ASCIDIAN NEWS*
Gretchen and Charles Lambert
206-365-3734
glambert@fullerton.edu or clambert@fullerton.edu
home page: http://depts.washington.edu/ascidian/
Number 66 June
2010
Thanks
to the many contributions, this is another packed issue, with 121 new publications
listed at the end. We hope you will find it very useful and interesting.
*Ascidian News is not part of the scientific literature and should not
be cited as such.
1. From Cristian
Cañestro: I'd like to share with the ascidian community that I have
recently moved to the Department of Genetics at the University of Barcelona
(Spain), where I'm setting up my own group working with Oikopleura,
among other chordate models. See our new publication Cañestro et al. 2010 at the end of this
newsletter. My new email address is canestro@ub.edu.
2. From Rosana Rocha: I have pdf’s of a large
number of old and difficult to obtain ascidian papers which I am happy to share
with anyone who needs them. You can contact me
(rmrocha@ufpr.br) and I will send
you the website address where you can download them.
3. From
from Changho
Yi: Another ascidian recipe! This one for ascidian whiskey—sure to
be a favorite! yichangho@gmail.com
.
“I saw Korean foods 'mong-gae bibim bap' in AN65. We enjoy Styela clava too. It was very funny in the cultural view, at least to me. Because I like that much. And I enjoy the 'mong-gae ju', means ascidian whiskey. It's little maniac, but many Koreans like that too. It's very simple:
We make that by pouring Soju (korean
traditional whiskeys) into hollow tunics of Halocynthia
roretzi.'removing inner part' but 'remaining body fluid' is
important. It provides unique smells.
Can you imagine its
taste? I like that much! J
http://www.ohmynews.com/NWS_Web/view/at_pg.aspx?CNTN_CD=A0000255144
[Editor’s note: the website is
all in Korean; a translation for the second recipe would be appreciated but the
photos speak for themselves!]
4. More
dining adventures with ascidians at these websites:
And another website for a
slightly different Korean bibimbap:
http://joongangdaily.joins.com/article/view.asp?aid=2918887
5. From Christian Sardet, BioMarCell
group UMR 7009 BioDev CNRS / Univ P et M Curie Paris 6,
Observatoire, Villefranche sur Me. csardet@gmail.com http://www.biologymultimedia.com
We posted on line episodes of our series of
short films called "Plankton Chronicles/ Chroniques du Plancton" as
part of a project I initiated in the context of the
Thanks for your suggestions
and comments.
1) Macroplancton gélatineux: http://vimeo.com/11871607
2) Ctenophores: orgies de couleurs: http://vimeo.com/11801925
3)Le plancton: http://www.vimeo.com/8698014
4)Pleurobrachia: http://www.vimeo.com/8572476
5)Ptéropodes, des mollusques qui nagent: http://www.vimeo.com/8021348
6)Larves et embryons: http://www.vimeo.com/8350760
7)Protistes, ambiance spatiale (no sound):http://www.vimeo.com/8350727l
They will soon be in English
and released for the general public. Thanks
for your suggestions and comments.
6. From Gretchen Lambert: I have a softbound
copy for sale for $65.00 of Van Name, W.G. 1945. The North and South American
Ascidians. Bull. Amer. Mus. of Nat. History. 476 pp., 31 black and white
plates. This was the personal copy of Dr. Patricia Dudley, who studied
parasitic copepods of ascidians. The money will go toward a student scholarship
at the
7. From Howard Reid, Executive Director, Mona Institute of Applied Sciences, 4
Belmopan Close, University of the West Indies, Mona Kingston 7, Jamaica,
Telephone: (876) 970-2021, (876) 970-2042, Fax: (876) 970-0289, Email: mias@uwimona.edu.jm,
Website: http://mias.uwimona.edu.jm .
For sale: compact
disc entitled: Caribbean Sea Squirts:
The Goodbody Collection produced by the Mona Institute of Applied Sciences
(MIAS) in collaboration with the Environmental Foundation of Jamaica. The CD is based on over fifty years of
research by author and zoologist, Professor Ivan Goodbody, on Caribbean Ascidiacea
at the University of the
Over 100 species of Sea Squirts (Ascidiacea)
have been recorded from shallow water environments in the
The CDs are informative, interactive, colorful,
and are tailored to attract scholars, researchers, students and marine
enthusiasts. The cost is US$75 plus shipping and handling and
can be purchased online through our website: http://www.discoverjamaica.com/shop/mona.html. Further information such as videos and
reviews can also be viewed on the website.
For purchases of 3 CDs or more,
the price is US$60 plus shipping and
handling and can be accessed through our office using the information
above.
8. From Ken Hastings,
Please mark your calendars. The Sixth International Tunicate Meeting
will be held in
See you in
WORK IN PROGRESS
1. From Serena
Teo tmsteolm@nus.edu.sg
and Serina Lee tmslscs@nus.edu.sg,
Tropical Marine Science Institute, National University of Singapore.
Currently our laboratory is conducting
surveys of marine fouling organisms in
2. The
hemolymph of the ascidian Styela plicata
contains heparin in intracellular granules of basophil-like cells. Cintia
Monteiro De Barros1,2; Giselle Cristina Ferreira Corrêa1;
Silvana Allodi2; Mauro Sérgio Gonçalves Pavão1. 1Laboratório
de Tecido Conjuntivo – IBqM – UFRJ – mpavao@hucff.ufrj.br 2Laboratório de Biologia de
Invertebrados – ICB – UFRJ – sallodi@histo.ufrj.br
Introduction: In vertebrate chordates, heparin is
synthesized on a specific protein core, forming the Serglycin proteoglycan
(PG). This PG occurs in secretory granules of some immune cells, such as tissue
mast cells and circulating basophils. In mast cells, the Serglycin PG is
glycosylated with heparin, whereas in basophil, chondroitin sulfate E is the
glycosaminoglycan (GAG) component of the serglycin protein [1]. Ascidians,
invertebrate chordates, contain different types of immune cells, occurring
either in the tissue or circulating in the hemolymph. These cells display
morphological and biochemical characteristics that resemble vertebrate mast cells
and basophils, respectively. In the ascidian S.plicata, a heparin GAG was shown to co-localize with histamine in
intracellular granules of only one type of hemolymph hemocyte, named
granulocyte [2].
Objective: To characterize the PG of the
ascidian granulocyte and their biological function.
Methods: The hemocytes were harvested from
the pericardial cavity of the ascidians. The PGs of the hemocytes were
extracted and purified in ion-exchange chromatography. The hemocytes were also
prepared for immunoelectronmicroscopy and western blotting using primary
anti-serglycin antibody. In addition, an in
vivo inflammatory assay was performed with the injection of E.coli into the tunic. After 5 days, a
fragment of the tunic was dissected, fixed for immunohistochemistry with
anti-serglycin and anti-MCP-1 antibodies.
Results: The Immunoelectronmicroscopy and
western blotting analyses with the anti-serglycin antibody indicate that a
serglycin-like protein co-localize with heparin and histamine in the
intracellular granules of the ascidian basophil-like cell (Figure 1). An
initial biochemical analyses indicate that the granulocyte heparin is linked to
a serglycin proteic core. Moreover, in
vivo inflammatory assays confirm the involvement of granulocytes (Figure
2). Theses results suggest that in primitive basophil-like cells from
invertebrate chordates, the serglycin PGs are glycosylated with heparin chains,
different from basophils from vertebrate chordates. Supported by CNPq,
References
[1] Iozzo, R.V. 1999. Marcel Dekker Inc.
[2] De Barros, C.M., Andrade, L.R., Allodi, S., Viskov, C.,
Mourier, P.A., Cavalcante, C.M., Straus, A.H., Takahashi, H.K., Pomim, V.H.,
Carvalho, V.F., Martins, M.A., Pavão, M.S.G. J. Biol. Chem. 2007. 282(3): 1615-1626.
3. From Anna Di Gregorio and2015@med.cornell.edu
Temporal
regulation of the muscle gene cascade by Macho1 and Tbx6 transcription factors
in Ciona intestinalis. In press, Journal
of Cell Science.
Kugler JE, Gazdoiu S, Oda-Ishii I, Passamaneck
YJ, Erives AJ, and Di Gregorio, A., Dept. of Cell and Developmental Biol.,
Weill Medical College of Cornell Univ., New York, NY 10065, USA
For
over a century, muscle formation in the ascidian embryo has been representative
of "mosaic" development. The molecular basis of muscle fate
predetermination has been partly elucidated with the discovery of Macho-1, a
maternal zinc-finger transcription factor necessary and sufficient for primary
muscle development, and of its transcriptional intermediaries Tbx6b and
Tbx6c. However, the molecular mechanisms by which the maternal
information is decoded by cis-regulatory modules (CRMs) associated with
muscle transcription factor and structural genes, and the ways by which a
seamless transition from maternal to zygotic transcription is ensured, are
still mostly unclear. By combining misexpression assays with CRM
analyses, we have identified the mechanisms through which Ciona Macho1
(Ci-Macho1) initiates expression of Ci-Tbx6b and Ci-Tbx6c, and we
have unveiled the cross-regulatory interactions between the latter
transcription factors. Knowledge acquired from the analysis of the
Ci-Tbx6b CRM facilitated both the identification of a related CRM in the
Ci-Tbx6c locus and the characterization of two CRMs associated with the
structural muscle gene fibrillar collagen 1 (CiFCol1). We
use these representative examples to reconstruct how compact CRMs orchestrate
the muscle developmental program from pre-localized ooplasmic determinants to
differentiated larval muscle in ascidian embryos.
4. Preparation
of pickle from Herdmania pallida, simple ascidian (In Press - World
Journal of Dairy and Food Science - IDOSI Publications)
M. Tamilselvi, V. Sivakumar, H. Abdul Jaffar Ali and R.D.
Thilaga 1 2 3 4 tamil_asc@yahoo.co.in
Dept. of
Dept. of
Dept. of
Biotechnol.
Dept. of
Zool.
Herdmania pallida, simple ascidian, belongs to the Subphylum Urochordata, Class
Ascidiacea, Family Pyuridae and is commonly available in Tuticorin coast of
[Personal note added by author: After
preparing the pickle, our family members were consuming it continuously for a
month. We received appreciation whole heartedly from the groups of people who
had the good opportunity to taste it. Really this pickle excelled in taste and
flavour. To my knowledge, I have not enjoyed this taste and flavour in the
pickles of molluscs, prawn and fish. This is the best one. As H. pallida contains calcium, protein,
iron, etc this species could be recommended for anemic, osteoporesis
patients. Further research is needed on these aspects.]
5. From Dr. H. A. Jaffar Ali: research activities carrying out by my students for their Ph.D programs.
a. Mrs. R..Radhalakshmi, Assistant Prof. in Zoology,VVV
College, Virudhunagar is doing research for her Doctoral Degree on Nutritional value of marine ascidians in
Indian coastal waters under the supervision of Dr.H.A.Jaffar Ali, Asst. Prof. of Biotechnology, Islamiah College,
Vaniyambadi, India with Co-Guide Dr. V.Sivakumar, Associate Prof. of Zoology,
V.O.C.College, Tuticorin. e-mail: jaffar_asc@yahoo.com
This work focuses on the nutritive value such
as protein, amino acid profile, carbohydrates, lipid, omega – 3 – fatty acids,
vitamins and micro & macro minerals of both simple and colonial ascidians along
the Indian coastal waters with the objective to pave the way for better
utilization of marine food sources and meet out the nutritional requirements of
the ever–increasing population in India.
b. Mr. A.Kallemullah Khan is doing his Ph.D. in the discipline
Marine natural products from
ascidians off Indian coastal waters and their biotechnological implications. This research work focuses on isolation
of marine natural products from chosen ascidians along the Indian coastal
waters and screening for their biological activities such as, antimicrobial,
antifungal, cytotoxic and antifouling activities. This work also focuses on
biosynthesis of silver/gold nanoparticles.
Half day ascidian taxonomy
workshop led by Gretchen Lambert.
Biology, Systematics and Biogeography Session:
Linking physiology,
biogeography and success of non-natives in subtidal communities in the Gulf of
Maine Dijkstra, Jennifer A.;
Westerman, E.L.; Brooks, C.; Harris, L.G.
Reproductive biology of Ciona intestinalis in Prince Edward Island, Canada Bourque,
Daniel
Spawning and culture techniques for
the invasive ascidian Didemnum
vexillum Fletcher, Lauren M.; Forrest, B.M.; Bell, J.J.
Monitoring ascidians on
natural and anthropogenic habitats in Bocas del Toro, Panama
Rocha, Rosana M.
Abundance and diversity of ascidians in
Pacific Panama: Differences with coastal development levels and distance from
the mainland Bullard, Stephan G.; Carman, M.R.; Rocha, R.M.;
Djikstra, J.A.; Goodwin, A.
Ascidians at the Pacific and
Atlantic entrances to the Panama Canal Carman, Mary R.; Rocha,
R.M.; Lambert, G.; Bullard, S.G.; Dijkstra, J.A.; Roper, J.J.; Goodwin, A.;
Baker, E.M.
Persistence of colonies of
the tunicate Didemnum
vexillum over a 5-year
period at specific sites on gravel habitats of Georges Bank, New England Valentine,
Page C.; Gallea, L.; Guida, V.; Blackwood, D.S.
TBA York, Amber
A time-series of morphological
development of the tunicate Didemnum vexillum
from settled larva to colony in
Ecology and Genetics Session:
Total genome analysis of
Didemnum vexillum Kott, 2002, a model organism for the study of marine
bio-invasions Gittenberger,
Adriaan; Stefaniak, L.M.
High resolution temporal patterns
of larval settlement: Do settlers avoid their spatial competitors? Hamilton,
John F.; Whitlatch, R.B.; Osman, R.W.
Multiplex beads assay as a
sensitive tool to detect tunicate aquatic invasive species in Prince Edward
Island sea water Siah, Ahmed; Pariseau, J.; McKenna, P.;
Sandjong, B.;Davidson, J.; Johnson, G.; Berthe, F.C.J.
Interspecific competition:
Effect of colonial tunicate presence on Ciona intestinalis recruitment Paetzold, S. Christine;
Davidson, John; Hill, J.; Davidson, Jeff
The vasa gene as a phylogenetic marker
for identification of invasive botryllids Tankouo-Sandjong,
Bertrand; Siah, A.
Ecology and management of invasive
solitary ascidians in New Zealand Willis, Kate; Nutsford, S.;
Floerl, O.
Investigations in Ciona intestinalis biofouling in Nova Scotia, Canada Vercaemer,
Benedikte; Sephton, D.; Nicolas, J-M.; Keays J.
Biology, ecology and trials of
potential methods for control of the introduced ascidian Eudistoma elongatum in Northland, New Zealand Page,
Michael, J.; Morrisey, D.J.; Handley, S.J.
Global phylogeography of the
solitary ascidian Styela
plicata Pineda, Mari Carmen; López-Legentil, S.;Turon, X.
Impacts Session:
Ecosystem consequences
of vase tunicate (Ciona intestinalis) infestation in mussel-producing estuaries
of Prince Edward Island Locke,
Andrea; Bourque, D.; Leger, C; Barkhouse, C.
An approach utilizing inhibitors of
invertebrate settlement and metamorphosis in preventing fouling of aquaculture
structures by ascidian pests Heasman, Kevin; Chautard, C.;
Dodgshun, T.; Mountfort, D.O.
First occurrence of the invasive
tunicates Ascidiella
aspersa and Didemnum vexillum in eelgrass habitat Colarusso, Phil;
Carman, M.R.; Grunden, D.W.; Chintala, M.M. Blackwood, D.S.
If You Build It, They Will
Come: Settlement of tunicates on artificial seagrass Grunden,
David W.; Carman, M.R.; Colarusso, P.; Chintala, M.M.; Blackwood, D.S.
Interspecific competition
between the colonial tunicates Botryllus schlosseri, Botrylloides violaceus and the cultured mussel Mytilus edulis, and efficacy of pressurized seawater as an
anti-fouling treatment Arens, Collin J.; Davidson, J.; Ramsay, A.
TBA Locke,
Andrea
Risk Assessment and Management Session:
Treatments to rid tunicates from cultured blue mussels Mytilus edulis Green-Beach, Emma; Carman, M.R.; Karney, R.C.;
Bagnall, P.L.; Carman, M.M.
Rapid Assessment for Didemnum vexillum in southwest New Brunswick Martin,
Jennifer L.; LeGresley, M.M.; Cooper, J.A.; Thorpe, B.; Locke, A.; Simard, N.;
Sephton, D.; Bernier, R.; Bérubé, I.; Hill, B.2; Keays, J.; Knox,
D.; Landry, T.; Lander, T.; Nadeau, A.; Watson, E.J.
Successes and failures:
proof-of-concept trials with new mitigation treatments against invasive
tunicates Paetzold, S.
Christine; Davidson, J.
Predicting the impacts of ocean
warming on a California fouling community using stage-structured population
modeling Sorte, Cascade
J.B.; Cockrell, M.L.
Tunicate monitoring in Nova Scotia
2005-2010: Program recap
2. Society for Integrative & Comparative Biology
(SICB),
a)
Comparative Proteomics: The Response of the ascidian congeners Ciona
intestinalis and C. savignyi to acute temperature stress. SERAFINI,
L., TOMANEK, L. Cal Poly, SLO. lserafin@calpoly.edu
Ciona intestinalis and C.
savignyi are congeneric tunicates that are commonly found along the Pacific
coast of
b) Proteomic
analysis of acute salinity stress in the two ascidian species Ciona savignyi
and C. intestinalis. KOMAN, James S.,
TOMANEK, Lars. Cal Poly SLO jskoman@gmail.com
The ascidian species Ciona savignyi
and C. intestinalis have been fully sequenced and thus allow analysis of
their proteomic response to environmental stress. We have chosen to analyze
their response to hyposaline conditions, which are known to occur during heavy
winter rains in the coastal regions in which Ciona populations live.
Such conditions often lead to population declines and it has been suggested
that it may contribute to determining the life history of these species along
the West coast of
c) Cellular
Basis for ascidian neurulation. SHERRARD, K.*; ROBIN, F;
CARVAJAL, D.; DANAHER, B.; DENG, W.; JOSHI, S.; MONTGOMERY, M.; SEMON, S.;
WHITE, D.; MUNRO, E.; Center for Cell Dynamics, Univ. of Washington; Center for
Cell Dynamics (U.W.) and Univ. of Chicago; Univ. de Antioquia, Columbia; Center
for Cell Dynamics (U.W.); SARS Institute, Bergen, Norway; Univ. of Pittsburgh;
Univ. of Washington; Univ. of Washington; Univ. of Alberta, Edmonton; Center
for Cell Dynamics (U.W.) and Univ. of Chicago kmsherra@alumni.uchicago.edu
Ascidians form a neural tube of only
a few hundred cells, providing an unparalleled opportunity to study this
fundamental morphogenetic process at the cellular level. Several distinct
subprocesses contribute to ascidian neurulation. First, primary invagination of
the neural plate is followed by axial elongation accompanied by mediolateral
cell-cell intercalation and oriented cell divisions. Second and concurrently,
constriction of the blastopore and medially-directed crawling bring epidermal
cells together at the posterior midline to initiate neural tube closure.
Finally, neural tube closure proceeds through anterior to posterior zippering
of both the neural tube and the overlying epidermal cells. Experiments with
explants and laser ablation reveal that neural plate invagination proceeds
normally in the absence of the posterior zipper-forming cells, but zippering
fails. Conversely, zipper initiation and propagation proceed normally in the
absence of the primary neural plate. Furthermore, unlike in vertebrates,
formation and elongation of the neural tube does not require the presence of a
notochord. A propagating zone of localized rho-kinase-dependent myosin
activation is required for blastopore closure and for zippering, but not for
invagination of the neural plate. Thus in ascidians, the complex process of
neurulation can be decomposed into, and understood in terms of, a set of
fundamental cellular mechanisms that are directly amenable to experimental
analysis.
d) A
propagating zone of localized protrusive and contractile activity drives
zippering and neural tube closure in ascidians. ROBIN, F.B.*; SHERRARD, K.M.;
MONTGOMERY, M.; SEMON, S.; MUNRO, E.M.; Univ. of Washington & Univ. of
Chicago; Univ. of Washington & Univ. of Chicago; Univ. of Washington; Univ.
of Washington; Univ. of Washington & Univ. of Chicago rbfr@u.washington.edu
The ascidian neural tube forms by
neurectoderm folding, followed by fusion of the neural folds at the dorsal
midline by a posterior-to-anterior "zippering" process. Using
time-lapse fluorescence microscopy, we found that neural closure is accompanied
by the constriction of a supra-cellular purse string-like actin cable that
develops at the boundaries between presumptive neurectoderm and lateral
epidermis. Significantly, constriction of the purse string is strongly biased
to it’s posterior end where it is accompanied by highly localized protrusive
activity and cortical contractility. Immuno-staining of fixed embryos and
time-lapse microscopy of live embryos revealed that the active RhoA and active
forms of Myosin are similarly localized to the highly contractile posterior
zone, which propagates posterior to anterior and cell to cell as zippering
proceeds. Blocking the Rho-pathway kinase ROCK with the inhibitor Y-27632 leads
to loss of localized activated Myosin and specifically causes the zipper to
collapse and the entire purse string to relax. Following fusion of opposed
neural fold cells, midline cells are first dragged anteriorly as the zipper
progresses further forward, then abruptly released as the apical domains of
presumptive dermal and neural cells lose contact. The result of this process is
to form two epithelia (one neural, one dermal) from a single initial epithelial
layer. Our data highlight the existence of a "morphogenetic
organizer" that coordinates supercellular force generation in time and
space to achieve the completion of an essential step in chordate development.
e) Neural
Tube Closure: Zipper Propagation in Ascidian Embryos. SEMON, Shelby N*; ROBIN, Francois;
SHERRARD, Kristin; MUNRO, Edwin; Univ. of Washington; MGCB, Univ. of Chicago;
Center for Cellular Dynamics, Univ. of Washington; MGCB, Univ. of Chicago snsemon@u.washington.edu
Ascidians are a member of the
chordate phylum and as such they undergo many of the same developmental
processes that other chordates undergo. The difference is that Ascidians have a
much smaller number of cells and larger cell size to embryo size ratio making
them an ideal system in which to study the fundamental processes involved in
neural tube closure. Focusing on the cellular processes involved in neural tube
closure, we used confocal microscopes for fixed and time lapse imaging with
fluorescent probes to carefully observe the cellular behaviors of control
embryos. We found that neural tube closure proceeds unidirectionally from
posterior to anterior in a behavior we call zippering. This behavior involves
three main processes: cell crawling, adhesion and contraction. Focusing on the
role of contractility, we found that there is a mechanically continuous actin
purse string that has myosin localized in an area of high contractility in the
boundary cells closest to the zipper. Using Y-27632, a drug that inhibits
RhoKinase-activated myosin to inhibit contractility at different stages during
zipper closure, we found that when Y-27632 was added near the beginning of the
zippering process, zippering did not proceed and when added late in the
zippering process, the zipper broke and the interior structures of the embryo
extended out of the anterior half. However, invagination of the floor cells of
the neural plate occurred normally in Y-27632 treated embryos. We conclude that
contractility is essential for zipper initiation and propagation but not a
driving force in the invagination that proceeds the zippering process.
f) Initiation
of Neural Tube Closure in Ciona Intestinalis. MONTGOMERY, M.S.*;
MUNRO, E.; SHERRARD, K.; ROBIN, F.; Univ. of Washington, Seattle monicm2@u.washington.edu
Ascidian neural tube closure
(zippering) is initiated by the assembling of cells and materials at a
posteriorly located center we are calling the zipper origin. The zipper origin
as a structure has not previously been described in the literature. To advance
our understanding of the prospective identity and morphological change of cells
in contact with the zipper origin, we created 3-D reconstructions through Amira
and 3-D Virtual Embryo of early neurula we fixed and stained in phalloidin. We
find that posterior-most muscle, neural plate, notochord, and epidermal cells
meet as they extend towards the zipper origin. With time-lapse imaging and
confocal microscopy, we show that initiation of neural tube closure occurs by
three main events: 1) cinching of the apical ends of muscle cells lining the
closing blastopore; 2) rolling-inward of the two posterior-most roof cells; and
3) crawling of posterior epithelial cells towards the zipper origin. We provide
evidence that this gathering at the zipper origin is significantly driven by
myosin contractility. We find the presence of monophosphorylated nonmuscle
myosin II at the same time and location of blastopore closure and building of
the zipper origin. We also find diphosphorylated nonmuscle myosin II
concentrated at the zipper origin at earlier and later stages corresponding to
the time of initiation of neural tube closure. We show further that inhibition
of nonmuscle myosin II through the
g)
Computational approach to neural tube closure. VELASQUEZ-CARVAJAL, D.*; SHERRARD,
K.M.; ROBIN, F.B.; MUNRO , E.M.; Univ. of Washington and Univ. of Antioquia;
Univ. of Washington; Univ. of Washington and Univ. of Chicago; Univ. of
Washington and Univ. of Chicago davidvelasc@gmail.com
Neural tube closure in ascidians
occurs by unidirectional zippering of epithelial and neural tube cells, and
involves several distinct cellular processes. On each side of the leading edge
of the zipper, filopodia protrude, make contact and pull the edges together
until the cells form new adhesions. At the same time, a “V” of localized
acto-myosin contractility is progressively activated in just a few cells as
they reach the zipper’s leading edge, and experiments inhibiting this
contractile “V” demonstrate it is essential for closure. It is not clear how
the filopodia, formation of adhesions, and localized contractility work
together to generate neural tube closure. We used a two-dimensional
computational model in which individual cells could exhibit these behaviors to
varying degrees to explore their relative importance. We found that a
combination of localized “V” contractility and filopodial action best
reproduced the shape changes observed in real embryos. In contrast, uniform
purse-string contractility failed to form a long tube, while filopodial action
alone was ineffective at sealing the tube. Localized “V” contractility could
drive normal closure kinematics, but only a for very restricted set of
parameter choices. Further, the model was able to reproduce an experimental
observation from partially ablated embryos, in which the “V” had a wider angle
than under normal conditions and neural tube closure failed. A concomitance of
different cell and tissue conditions are needed for a morphogenetic process to
occur properly, and computional modeling provides a means, complementary to
experiments, to separate key features essential to such processes.
h) Ascidian
neural tube morphogenesis proceeds normally following ablation of the notochord DANAHER, B.*; MUNRO, E.; SHERRARD,
K.; ROBIN, F.;
Ascidian neurulation proceeds through
concurrent invagination and extension of a monolayer neural plate. The
underlying notochord forms simultaneously through invagination and convergent
extension of a monolayer plate into a cylindrical rod. The notochord is a
likely candidate for effecting neural morphogenesis: it is the substrate for
neural tissue throughout neurulation, and its robust convergent extension is a
probable source of extensile force in the ascidian tailbud. Here we use laser
ablation at the 64-cell stage and time lapse confocal microscopy to examine
neural morphogenesis in the absence of a notochord. We show that neural plate
organization, invagination, and neural tube closure all continue normally.
Neural tube extension is slightly limited, but neural cells retain normal
organization and significant elongation. Our results indicate that neural
morphogenesis is a robust process, and suggest alternative driving forces for
ascidian tailbud elongation.
i) From
Genome to Development in Amphioxus. HOLLAND, L.Z.*; SHORT, S.; Univ. of California San Diego;
Portsmouth Univ, U.K. lzholland@ucsd.edu
Although gnathostome genomes
(mammals, fish) were the first deuterostome genomes sequenced, genomes of most
major deuterostome groups have now been sequenced. These include an agnathan
(lamprey), ascidian and appendicularian tunicates, a cephalochordate
(amphioxus) an echinoderm (sea urchin) and hemichordate. Comparative genomics
has answered many questions (e.g. the timing of whole genome duplications) but
has also raised awareness of how little is known about how genes direct
formation of a functional organism. Heritable traits not directly encoded by
the genome (epigenetics) have assumed increased importance in this regard. One
such epigenetic phenomenon is alternative splicing. Paired box (Pax)
transcription factors are involved in development of such endocrine organs as
the thyroid and its homolog, the endostyle (in larval lampreys, tunicates and
amphioxus) [Pax2/5/8], the thymus [Pax3/7], pharyngeal endoderm [Pax1/9] and
adenohypophysis [Pax4/6]. Alternative splicing can affect the DNA binding
domains of Pax factors and/or the c-terminal transactivation and repression
domains. Some splice forms are evolutionarily conserved, suggesting vital
functions, while others are not. Pax splice forms are differentially expressed
during development in both amphioxus and vertebrates. To investigate the
importance of Pax isoforms in development, we used antisense morpholino-oligonucleotides
(MOs) to knock down function of all isoforms of amphioxus Pax2/5/8 and Pax1/9
as well as that of specific isoforms. Our results show that knockdown of all
isoforms of these two genes with an MO complementary to the ATG start codon
gives the same phenotype as using a splice-blocking MO to convert the major
isoform expressed in early development to a minor one. These results suggest
that the minor isoforms may function to modulate function of the major ones and
underscore the importance of post-transcriptional mechanisms for gene function.
j)
Amphioxus thyroid hormone signaling pathway and the evolution of metamorphosis
in chordates. PARIS,
M*; ESCRIVA, H; SCHUBERT, M; BRUNET, F; BRTKO, J; CIESIELSKI, F; JAMIN, E;
CRAVEDI, JP; RENAUD, JP; SCANLAN, TS; HOLLAND, ND; LAUDET, V; Univ. of
California, Berkeley; Lab. Arago, Banyuls sur mer; Ecole Normale Superieure de
Lyon; Ecole Normale Superieure de Lyon; Inst. of Experimental Endocrinol.;
AliX, Illkirch; INRA, Toulouse; INRA, Toulouse; AliX, Illkirch; Oregon Health
& Science Univ., Portland; Scripps Inst. of Oceanography, La Jolla; Ecole
Normale Superieure de Lyon mparis@berkeley.edu
Metamorphosis is a spectacular
post-embryonic developmental stage, allowing a larva to become a juvenile. In
the chordate lineage, that comprises vertebrates, urochordates like tunicates
and cephalochordates like amphioxus, the morphological changes during
larva-to-adult transitions vary extensively from one species to another,
suggesting that metamorphosis may have arisen several times in the chordate
lineage. Does the molecular determinism of metamorphosis in this group reflect
this morphological diversity? In the well-studied vertebrates, metamorphosis is
triggered by thyroid hormones (THs) binding to their receptor TR, member of the
nuclear hormone receptor superfamily. In order to get better insight into the
evolution of the molecular determinism of metamorphosis in chordates, we
focused on the most basal chordate amphioxus. Combined biochemical and
phylogenetic approaches allowed us to establish that amphioxus produces various
THs through metabolic pathways homologous to vertebrate ones. Then we showed
that TH production as well as TH-dependent TR activation are essential for
metamorphosis induction in amphioxus, like in vertebrates, with the slight
difference that the active TH is not T3, the classical vertebrate TH, but
possibly its derivative TRIAC. Consequently the homology of metamorphosis in
chordates is revealed by the conservation of its triggering mechanism. This
suggests that the evolution of metamorphosis in chordates is marked by the
conservation of the couple TH/TR whereas other parts of the regulatory network
may change to underlie the morphological diversity observed nowadays.
k) Tunicate
genomics: a window into chordate development and evolution ZELLER, R.W.; San Diego State Univ.
rzeller@sciences.sdsu.edu
Tunicates, particularly ascidians,
are an excellent biological system in which to study gene regulatory mechanisms
important during embryological development. Because of their phylogenetic
position within the chordates, tunicates will provide insight into the
evolution of chordate gene regulation. Three tunicate genomes have been
sequenced to date: two ascidians – Ciona intestinalis and C. savignyi,
and one larvacean – Oikopleura dioica – possessing the smallest known
chordate genome. This wealth of genomic information, coupled with extensive EST
collections from all three species, has allowed researchers to initiate
genome-level investigations of tunicate development. The Ciona genome
encodes about 15,000 genes, but is one twentieth the size of typical vertebrate
genomes. Tunicate genomes lack extensive gene duplication events thus gene
regulatory mechanisms are believed to be simplified compared to vertebrates. A
review of the current Ciona genome assembly will be presented and
examples from genome-scale research efforts will be discussed.
l) Genomics
of Amphioxus and Tunicates: Tracing the Evolution of the Endocrine System. SHERWOOD, Nancy M.*; ROCH, Graeme J.;
TELLO, Javier A.; Univ. of Victoria nsherwoo@uvic.ca
The sequencing of the genomes for amphioxus
and tunicates has allowed us to examine the foundation of the endocrine system
in species that evolved at the transition between invertebrates and
vertebrates. In regard to reproduction, the neuroendocrine system in these
early chordates is vertebrate-like, but the pituitary and gonadal endocrine
hormones and receptors are clearly lacking a number of vertebrate components.
In tunicates (Ciona intestinalis and C. savignyi), six
gonadotropin-releasing hormones (GnRH) and four receptors were cloned. The six
GnRH peptides selectively activated recombinant forms of their receptors and in
vivo spawning. In amphioxus (Brachiostoma floridae), four GnRH receptors
were cloned and expressed in COS7 cells; their pattern of response provides
evidence that both invertebrate-type and vertebrate-type GnRH receptors exist
in amphioxus. In contrast, functioning neuroendocrine systems in basal
chordates do not appear to activate specific pituitary hormones, as neither FSH
nor LH hormones/receptors are identified in the amphioxus or tunicate genomes.
Rather it is likely that the GnRH peptides act directly on the gonads. Only
amphioxus and not Ciona has the necessary enzymes for biosynthesis of
sex steroids. Also, both chordate groups have a small number of nuclear
receptors but only amphioxus has steroid-type nuclear receptors. Outside of
reproduction, the insulin-IGF family and receptors, essential for growth,
development and metabolism, are present in both amphioxus and tunicates along
with other hormones including the osmoregulatory hormone stanniocalcin. The
endocrine components are homologous to those in vertebrates and reveal the
foundation of the chordate endocrine system before the genomic duplications in
early vertebrates.
m) A Dual
Origin of the Pituitary Primordium in the Ascidian. KANO, S*; SATOU, Y; DESCHET, K;
MARTIN, P; HAEUSSLER, M; JOLY, JS; CNRS, Gif-sur-Yvette, France; Kyoto
University, Kyoto, Japan; CNRS, Gif-sur-Yvette, France; INRA. Jouy-en-Josas,
France; CNRS, Gif-sur-Yvette, France; CNRS, Gif-sur-Yvette, France kanoic@ciona.info
The pituitary is an essential
endocrine organ in the vertebrates. While the urochordate possesses no distinct
pituitary organ, it has been long proposed that the ascidian neural complex (NC)
composes homologous organs to the brain and the pituitary. Recent molecular
data suggests that the ciliated funnel (CF), one of the NC components, is the
most probable candidate as several placodal genes including CiPitx are
expressed at the ectodermal stomodaeum and the CF, respectively, in embryonic
and the adult stages (Boorman and Shimeld, 2002; Christiaen et al.,
2002). To reinforce this hypothesis with insights from the developmental
process, we conducted lineage analyses mainly using a photo-convertible
fluorescent protein Kaede driven with promoters recapitulating endogenous
expressions of CiPitx and CiNut (the neural tube marker). We
validated that a part of the ectodermal stomodeaum invaginates, separates from
the major part and gives rise to the distal tip of the CF. Furthermore, we
revealed that the proximal domain of the CF, which is adjacent to the distal
tip, is derived from the neuroectodermal "dorsal duct". Thus, the
ascidian CF has a dual origin and its organogenesis resembles the vertebrate
pituitary. We then investigated whether the ectodermal CF expresses genes
relevant to an endocrine activity like the vertebrate pituitary. However, we
could not confirm it. It is likely that a pituitary primordium is present in
the ascidian, but that the endocrine activity of the pituitary is a vertebrate
innovation presumably with evolutions of adenohypophyseal transcription factors
which terminally differentiate hormone-secreting cells.
n) Multiple
roles of retinoic acid in the pharyngeal endoderm development of amphioxus. KOOP, D.*; HOLLAND, L.Z.; Univ. of
California, San Diego dkoop@ucsd.edu
In the cephalochordate, amphioxus, the
pharyngeal endoderm gives rise to Hatschek’s pit (homologous to the vertebrate adenohypophysis),
endostyle (homologous to the vertebrate thyroid) and gills. However, in
vertebrates, pharyngeal structures receive a major contribution from neural
crest cells, whereas amphioxus lacks neural crest facilitating the study of the
role of the endoderm in pharyngeal patterning. In both amphioxus and
vertebrates homologous suites of genes pattern the pharyngeal endoderm. These
include Tbx1/10, Eyes absent, Six genes and Pax
genes. Our previous studies have demonstrated that retinoic acid (RA) signalling,
mediated by Hox established the posterior limit of the pharyngeal endoderm.
Here we present a second role for RA signalling in the development of the
gills. To investigate the role of RA signalling during pharyngeal endoderm
morphogenesis, we examined the effects of late RA treatments on the genes that
pattern the gill pimordia such as Six and Pax genes. Our results
show that at later stages in development RA does not inhibit gill primordia
formation but does plays an important role in regulating gene expression and
apoptosis in the forming gill slits. These results suggest that in amphioxus,
as in vertebrates, pharyngeal development involves a complex interaction of
signalling pathways, often playing multiple roles.
o) Potential resistance
of Antarctic ascidians to sympatric bacterial epibiosis. KOPLOVITZ, G*; MCCLINTOCK, J.B.;
AMSLER, C.D.; BAKER, B.J.; Univ. of Alabama at Birmingham; Univ. of Alabama at
Birmingham; Univ. of Alabama at Birmingham; Univ. of S. Florida gilkop@uab.edu
Both biotic and abiotic surfaces in
benthic marine environments are subject to fouling by bacteria, protists and
macroinvertebrate larvae. Although in certain circumstances epibiosis may be beneficial
to the basibiont (the organism being fouled), for example, through the
provision of vitamins and nitrogenous compounds, by in large, fouling is more
harmful than beneficial. A large variety of fouling organisms are commonly
found on the surfaces (tunic) of ascidians. These include bacteria, algae (such
as diatoms), bryozoans and hydroids, as well as other macroinvertebrates. The
focus of this study was to assess the incidence of antimicrobial activity in
both lipophilic and hydrophilic crude organic extracts of a suite of solitary
and colonial ascidians from the western
p) Does
temperature affect Whole Body Regeneration (WBR) rate in Botrylloides
spp? PINNICK, G.L.*;
COHEN, C.S.; San Francisco State Univ. sarahcoh@sfsu.edu
Botryllid ascidians, colonial marine
chordates, possess unique modes of propagating and regenerating that make
robust models for studying the biological pathways for tissue regeneration.
Here, we test the effect of temperature on regeneration ability and rate, as
mediated by the retinoic acid (RA) pathway that is common in chordate embryonic
development. Colonies of Botrylloides sp from 2 sites in
q) Bloody
Whole Body Regeneration!
BROWN, FD*; KEELING, EL; LE, AD; SWALLA, BJ; Univ. of Washington; Univ. de
los Andes, Bogotá; Univ. of Washington; Calif. Polytechnic State Univ. San Luis
Obispo; Univ. of Washington federico.brown@tuebingen.mpg.de
Colonial ascidians exhibit one of the
most extreme cases of regeneration. Upon removal of all individuals in a colony
of Botrylloides violaceus, the vascular network and blood left within
the tunic of the colony reorganizes, and aggregates of blood differentiate into
buds. One of these buds continues to complete regeneration of a whole
individual. Using phase contrast microscopy, time-lapse video recording and
detailed histological studies of regenerating colonies, we describe the
earliest events of regeneration. We examine the pattern of cell proliferation
by immunohistology using proliferating cell nuclear antigen (PCNA) antibodies.
Next, we report the expression of piwi, a stem cell maintenance marker involved
in microRNA processing and stem cell maintenance, in hemocytes surrounding the
early regenerates. We rarely found Piwi or PCNA in differentiating tissues
during vascular budding, suggesting that cells that form the epithelial tissues
during budding and regeneration originate mostly from circulatory hemocyte
precursors, and likely include stem cell progenitors. First attempts to
establish lineage tracing are now in progress. Preliminary results using the
nuclear stain DAPI (<360 nm excitation range to avoid endogenous
autofluorescence) show that it can be reliably followed in the colony up to a
month after labeled hemocyte injection. We find DAPI labeled cells integrate
into tissue epithelia of different germ layers. Taken together, we propose that
multiple stem cell types occur within the hemocytes, and that they undergo
proliferation in the vasculature before differentiating into epithelial
tissues.
r) Colony
fusion common in a colonial ascidian. WESTERMAN, E.L.*; DIJKSTRA, J.A.; HARRIS, L.G.; Yale Univ.;
Wells National Estuarine Research Reserve; Univ. of New Hampshire erica.westerman@yale.edu
Many benthic colonial invertebrates
have the ability to fuse and form chimeras with compatible colonies. Botryllid
ascidians fusion rates have been determined for different populations and
species by random sampling and fusion testing individuals. However, natural
fusion rates over time nor their influence on colony size have not been
documented. We deployed six settlement panels to monitor the growth of single
genotypes of ,Botrylloides violaceus and Botryllus schlosseri
from July to September 2006 in
s) Dispersal
limitation and post-settlement survival of an introduced ascidian (Botrylloides
violaceus) in
Distributions of introduced species
are often patchy; however, the mechanisms regulating these patchy distributions
are poorly understood. Sessile organisms with short-lived larvae provide an
opportunity to test whether these distributions are dispersal-limited or
determined through post-metamorphic survival and growth. Here we used the
non-native colonial tunicate Botrylloides violaceus to examine the roles
of dispersal and predation in determining its distribution by transplanting
recently settled juveniles to locations with and without adult B. violaceus
colonies. Survival and growth were not different between caged and uncaged treatments
at any site, suggesting that predation is not controlling the distribution of
this species. However, survival and growth were different among locations. One
site without established colonies had significantly lower growth and survival
than all others, suggesting the importance of abiotic factors at this site. The
other site where adults were absent had similar growth and survival to sites
with established colonies, indicating that dispersal limitation is more
important at this site than abiotic factors. Our study suggests that the
distribution of B. violaceus is limited by both dispersal and
environmental conditions that affect juveniles after settlement.
t) Form,
function and flow in the plankton: Jet wake structure and swimming performance
of pelagic tunicates. SUTHERLAND,
K. R.*; MADIN, L. P.; MIT/WHOI Joint Program in Oceanography; Woods Hole
Oceanographic Institution krakow@whoi.edu
Salps are barrel-shaped marine
invertebrates that swim by jet propulsion. Morphological variations among
species and life-cycle stages are accompanied by differences in swimming mode.
The goal of this investigation was to compare propulsive jet wakes and swimming
performance variables among morphologically distinct salp species (Pegea
confoederata, Weelia (Salpa) cylindrica, Cyclosalpa affinis) and relate
swimming patterns to ecological function. Using a combination of in situ dye
visualization and particle image velocimetry (PIV) measurements, we described
properties of the jet wake and swimming performance variables including thrust,
drag and propulsive efficiency. Locomotion by all species investigated was
achieved via vortex ring propulsion. We found that the slow-swimming P.
confoederata produced the highest weight-specific thrust (T= 53 N kg-1)
and swam with the highest whole-cycle propulsive efficiency (ηwc=
55%). The fast-swimming W. cylindrica had the most streamlined body
shape but produced an intermediate weight-specific thrust (T= 30 N kg-1)
and swam with an intermediate whole-cycle propulsive efficiency (ηwc=
52%). Weak swimming performance variables in the slow-swimming C. affinis,
including the lowest weight-specific thrust (T= 25 N kg-1) and
lowest whole-cycle propulsive efficiency (ηwc= 52%), may be
compensated by low energetic requirements. Swimming performance variables will
be considered in the context of ecological roles and evolutionary
relationships.
3. 5th Intl. Tunicate Meeting, Naha-city,
a. Differentiation of
rostral sensory neurons in the larva of the ascidia Botryllus schlosseri.
Federico Caicci, Giovanna Zaniolo, Valentina Degasperi, Fabio Gasparini,
Paolo Burighel, Lucia Manni, Dept. of Biology, Univ. of Padova, Italy.
The larva of the colonial ascidian Botryllus schlosseri bears three
anterior papillae for selection and settlement on the substrate. They are
defined “ganglionated” for the presence of sensory neurons grouped in a
ganglion-like structure at their base. We investigated at morphological
(ultrastructural and immunocytochemical) level the differentiation of the
rostral epidermis during late embryogenesis, larval swimming stage and onset of
metamorphosis. The rudiments of papillae appear in early tail-bud stage as
protrusions bearing at apex bipolar neurons. These neurons differentiate into
two types of ganglionic neurons (central and peripheral), with long, rod-like
dendritic terminations, which in larval stage become exposed to the sea-water.
At the base of papillae and in the adjacent epidermis, other scattered sensory
neurons extend into the tunic long-sinuous dendrites. We identified these
neurons as equivalent to rostral trunk epidermal neurons described in Ciona intestinalis (Takamura, 1998). In B. schlosseri, at onset of metamorphosis, the papillae
retract and neurons undergo involution by apoptosis. On the base of dendrite
features and larva behavior, we propose that ganglionic neurons are
mechanoreceptors, whereas rostral trunk epidermal neurons are chemoreceptors.
During embryonic development the epidermis among papillae acquires
progressively secretory features culminating in apocrine secretion at
settlement. We suggest that this interpapillary epidermis is involved in
production of sticky substances which render the tunic suitable for temporary
adhesion of the larva to the substrate.
b.Gene expression during body muscle
differentiation in the colonial ascidian Botryllus
schlosseri. V.
Degasperi*, S.M. Shimeld**, F. Gasparini*, L. Manni*, P. Burighel*.
*Dept. of Biology,
Ascidians display
three types of muscles during their life: striated in the larval tail and
heart, and smooth in the post-metamorphic sessile phase. The larval and cardiac
muscles have an arrangement of myofilaments like the striated muscle of
vertebrates. Instead, the smooth body-wall musculature has intermediate
characters between smooth and striated muscle of vertebrates. A great number of
ascidians form colonies constituted of clonal individuals (blastozooids)
originated by asexual reproduction. We studied the musculature in Botryllus schlosseri analysing its
organization, differentiation with electron microscopy. Moreover, we followed
gene expression of muscle actin and troponin T in the larva and during the
development of blastozooids, beginning from the early bud stage to adult and
regression stage. We isolated and characterised two transcripts from colonies
that resulted homologous to muscle genes of solitary ascidians: a muscle-type
actin (BsMA2), a cytoplasmic-type
actin (BsCA1) and a troponin T (BsTnT-c). Moreover, we obtained also the
genomic sequences coding for BsMA2
and BsCA1. Phylogenetic analyses
showed a close relationship between urochordates and vertebrates muscle genes.
The BsMA2 and BsCA1 genomic sequences were compared in the exon-intron organization
with other muscle and cytoplasmic–type actin genes of both invertebrates and
vertebrates. Our data revealed that intron positions are conserved in ascidians
and in the other deuterostomes. We detected the expression of the two genes by in situ hybridization on section (ISH)
throughout the blastogenetic cycle of B.
schlosseri. The ISH, in parallel with phalloidin staining experiments,
showed that the first diffuse signal of BsMA2
and BsTnT-c labels differentiating
muscles which appear in the intersiphonal area of young buds. Then, the muscle
fibres differentiate into the body-wall, while an intense expression only of BsMA2 marks the myocardium just when it
begins contractions. Thus, all the phases of muscle development and regression
were documented by an integrated study showing the close correspondence of in situ expression of BsMA2 and BsTnT-c, phalloidin signal and ultrastructure.
4. 12th Congress of the
European Soc. for Evolutionary Biology,
Characterization of a MuSashI-like
transcript in a colonial chordate, phylogenetic analysis of the protein group
and differential expression patterns in sexual versus asexual development.
F. Gasparini, V. Degasperi, E. Ruffoni, P.
Burighel, L. Manni. Dipartimento di Biologia, Università degli Studi di Padova
Tunicates
are the unique chordates to possess species reproducing sexually and asexually.
Between them, Botryllus schlosseri
forms similar organisms (oozooids and blastozooids) trough embryogenetic and blastogenetic
pathways respectively. We here illustrate the characterization and expression
pattern, during both pathways, of a transcript for a gene that we named BsMSI. We demonstrate that BsMSI falls into MuSashI-like (MSI-like)
group, formed by MSI1, MSI2 and DAZAP1 genes. They encode for
RNA-binding proteins phylogenetically related to other protein groups: the TARDBP
and several hnRNPs. These proteins share same modular domain structure: a 2xRRM
motif. Analyses show that MSIs-like and 2xRRM-hnRNPs had a common origin from a
TARDBP type, and that 2xRRM-hnRNPs form a monophyletic group. A unique
MSI-like, orthologous to DAZAP1, was recognized in tunicates. We hypothesize
that, as MSIs are widely present in metazoans, tunicates have lost them during
their evolution. In vertebrates MSI1
is considered a stem cells marker, but also MSI2 and DAZAP1 are involved in
differentiative processes. BsMSI is
expressed in all the tissues of developing buds. This ubiquitous blastogenetic
expression differs from the embryogenesis one, which varies spatio-temporally
according to the differentiation of embryonic, larval or oozooid tissues.
Interestingly, BsMSI expression ends
in differentiated or regressing structures (adult blastozooids, differentiated
larval structures). Because the BsMSI
expression pattern doesn’t overlap
between blastogenesis and embryogenesis, we speculate it operates substitutive
functions of the vertebrates orthologues DAZAP, MSI1 and MSI2, and that the
function, related to differentiation or tissue maintaining, varies during the B. schlosseri life cycle.
5. XIth sci. meeting
of the Italian Assoc. of Developmental and Comparative Immunobiology 24-26
February 2010, Univ. of Modena & Reggio Emilia, Modena,
Natural apoptosis during the blastogenetic cycle of
the colonial ascidian Botryllus
schlosseri. F. Schiavon, L. Manni, M.Del Favero, L. Ballarin. Dipartimento di Biologia, Università
di Padova, Padova, Italy
Colonies of the compound ascidian Botryllus schlosseri undergo regular generation
changes during which adult zooids are progressively resorbed and replaced by
growing buds. The generation change, or take-over, is characterized by massive
cell death by apoptosis, changes in the expression of surface molecules by
senescent cells of zooid tissues and recruitment of circulating phagocytes in
zooid tissues which assure the complete clearing of the dying cells. The entire
process lasts 24-26 h at
6. Upcoming
symposium: The 7th Intl. Symp. on the Chemistry and Biol. Chemistry
of Vanadium, October 6 - 9, 2010,
Vanadium chemistry and biochemistry have
become more attractive in part because of the synthetic utility of several
vanadium complexes and in part because of new findings that vanadium compounds
have insulin-mimic and anti-tumor properties. In addition, the discovery of
several vanadium enzymes and proteins from marine organisms (including
ascidians) are the subject of intensive research. Organizing Committee: Hitoshi
Michibata (Chair),
7. ABCD meeting; Stem cells, development and
regenerative medicine,
Role of the alternative transcripts and targets of
the Ci-POU IV gene in the development
of the peripheral nervous system of the tunicate Ciona intestinalis.
Raoul Manenti*, Giuliana Zega*, Simona Candiani§, Mario
Pestarino§, Fiorenza De Bernardi*, Andrea Pasini°, Roberta Pennati*,
°Instit. de
Biol. du Développement de Marseille Luminy (IBDML), UMR6216, CNRS/Univ. de
Some members of the POU gene family regulate the neural patterning and differentiation in both vertebrate and
invertebrate embryos. The tunicate Ciona
intestinalis has only three genes encoding for POU transcription factors
and the gene Ci-POU-IV is
specifically expressed in all the peripheral nervous system (PNS) territories
and in some cells of the central nervous system during development. Within
chordates, tunicates represent the sister group of vertebrates and their larvae
have a typical chordate body plan. Notably larval nervous system is formed by
few cells whose organization mirrors that of vertebrates. The aim of this work
was to study the role played in neural differentiation by the two alternative
transcripts of Ci-POU-IV, we discovered, and to identify the targets of this
gene.
We
designed Morpholino oligos to perform gene knock-down experiments for the
different isoforms, a short and a long one. Preliminary results from these
experiments revealed that the expression of the serotonin rate-limiting
synthesis enzyme, tryptophane hydroxylase (TPH), and glutamate transporter
(vGlut) could be regulated by the long transcript. To verify if the alternative
transcripts are expressed in different neuron populations, we synthesized a
probe selective for the short isoform. The in situ hybridizations, compared to
the whole expression profile of Ci-POU-IV,
showed a lack of expression of the “short” form in the sensory epidermal
neurons of the trunk. Furthermore, we
look for the Ci-POU-IV targets by a
bioinformatic approach. The possible consensus sequences were obtained by
bibliographic research of those known for the POU IV family in both
invertebrates and vertebrates. We used these sequences to build a matrix that
was employed to perform a bioinformatic research in the whole C. intestinalis genome with a software
elaborated by the Lemaire team of the IBDML of Marseille. We identified 19
possible targets of Ci-POU-IV and we
preliminary selected 8 regions corresponding to 6 genes, including TPH. The
activity of the selected regions is being evaluated. Results from this work
allows us to hypothesize that the two isoforms play different roles during
nervous system differentiation. and will help us to delineate the signal
cascade of Ci-POU-IV during PNS
differentiation.
THESIS ABSTRACTS
1. The effects of Didemnum vexillum overgrowth
on Mytilus edulis biology and ecology.
Linda A. Auker, Dept. of Biological Sci.,
Didemnum vexillum is an invasive colonial ascidian in the
Overgrowth had a negative impact on mussel
growth. Tissue index and lip thickness were negatively affected as the mussel
lip margin was overgrown. Overall mussel growth was significantly higher in
control mussels by the end of the experiment. The pattern of spawning and gonad
development was reversed in overgrown male mussels from the control mussels.
Predation studies showed a potential positive effect for the mussel, as crabs
consumed more control mussels than overgrown mussels in both a choice study and
a consumption study. Finally, winter mussel settlement in 2008-2009 was lower
than historical 1980-1981 settlement, and there was a decrease in mussel
plantigrades with D. vexillum recruits. These studies show tradeoffs in
the effects of overgrowth by D. vexillum; growth and reproduction are
inhibited, while predation is decreased. As mussels are an important source of
food and habitat for other
2. Localization
and identification of protein kinase C subtypes in ascidian sperm activation. Senior Thesis by Rolando Rui,
In Ascidia ceratodes, sperm activation is
characterized by a morphological change known as mitochondrial
translocation. This event is an
actin:myosin-driven process and is dependent on internal calcium ion (Ca2+i)
release by the ER. Ca2+i
release is dependent on the action of inositol 1,4,5-trisphosphate via
signaling of the G-protein coupled receptor.
Ca2+i activates protein kinase C (PKC), which
facilitates signal transduction leading to mitochondrial translocation. Based on Rim-1 fluorescence labeling, we
propose that in activated but not unactivated sperm cells, the elevation of Ca2+
concentration from ER stores stimulates PKC8 to relocate from
mitochondrion-associated sites to the plasma membrane where it triggers a
pathway leading to Ca2+ entry and myosin activation. Myosin, in turn, powers mitochondrial
translocation. We also hypothesized that
conventional PKCα subtype is present in ascidian sperm. To test these hypotheses, cytosolic-, and
mitochondrial-rich fractions were prepared and checked for purity using
succinate dehydrogenase (SDH) and lactate dehydrogenase (LDH) enzymatic assays. PKC activity was tested in the two fractions
with a PKC assay kit. Various PKC
pseuodsubstrates (gift of Dr. Driss Zoukhri,
NEW PUBLICATIONS
Aiello, A.,
Fattorusso, E., Imperatore, C., Menna, M. and Muller, W. E. 2010. Iodocionin, a
cytotoxic iodinated metabolite from the Mediterranean ascidian Ciona
edwardsii. Marine Drugs 8: 285-291.
Akasaka, M., Harada,
Y. and Sawada, H. 2010. Vitellogenin C-terminal fragments participate in
fertilization as egg-coat binding partners of sperm trypsin-like proteases in
the ascidian Halocynthia roretzi. Biochemical and Biophysical Research
Communications 392: 479-484.
Astorga, M. P.,
Guinez, R. and Castilla, J. C. 2009. Genetic divergence in the ascidian Pyura
praeputialis (= Pyura stolonifera) (Heller, 1878) from mainland
Auger, H., Sasakura,
Y., Joly, J. S. and Jeffery, W. R. 2010. Regeneration of oral siphon pigment
organs in the ascidian Ciona intestinalis. Developmental Biology 339:
374-389.
Ballarin, L. and Kawamura,
K. 2009. The hemocytes of Polyandrocarpa mysakiensis: morphology and
immune-related activities. Invertebrate Survival Journal 6: 154-161.
Ballarin, L. and
Manni, L. 2009. Stem cells in sexual and asexual reproduction in Botryllus
schlosseri (Ascidiacea, Tunicata): an overview. In Stem Cells in Marine
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