GEN551 Berg
Paper for 20 Oct 2000
Kockel, L., J. Zeitlinger, L. Staszewski, M. Mlodzik, and D. Bohmann. 1997. Jun in Drosophila development: redundant and nonredundant functions and regulation by two MAPK signal transduction pathways. Genes Dev.11: 1748-1758. The authors examine the function of the Jun transcription factor in embryonic and eye development. Although Jun is essential for dorsal closure, surprisingly, clones of null alleles produce little effect in the eye. We will discuss the logic and methods for evaluating redundant genetic pathways.
Questions for Thought
1. Background: On the dorsal side of the Drosophila embryo, a small region called the amnioserosa must be closed over by more lateral cells moving upward and towards each other in a purse string fashion. This process is called dorsal closure; mutations that affect this process produce embryos with open tops (basket, kayak, canoe, etc.). Don't worry about the process, just view dorsal closure as another biological pathway.
What is the logic behind this work? Why are the authors studying Jun and its kinases, JUNK and JUNKK?
The authors use three approaches to investigate Jun in embryonic development. What are these methods and how does the information we learn from them differ?
How do the authors obtain mutations in jun?
2. Why do the authors think Jun functions in the eye? Given the results here, what kind of evidence might they have had previously to suggest a role for Jun in this tissue? What methods might have been used? Don't look up these papers - use your knowledge of genetics to think of two different approaches that might have been used to examine Jun function in the eye.
The authors make clones of jun
1 and jun2 alleles in the eye. What is the result? How does this result compare with previous studies? They suggest two hypotheses to explain this discrepancy. Are there other interpretations for this phenomenon?How do they test their hypotheses? (Figure 7) What is the logic behind this approach? That is, how do jun
ala and junasp function and why would that affect the result? Do you agree with their interpretation? How general is this method?3. The authors believe some other function can act redundantly for Jun in the eye. They use two different types of approaches to address this issue. Both are based on creating a "sensitized" background. What are these methods and how do they differ from that used by Simon et al.? What are their results?
4. If jun function is redundant, why does loss of one copy fail to complement loss of one copy of rl?
How could you use this information to identify the redundant function for jun? What type of screen would you design? What mutations would you use and why?
5. Suppose a redundant function acts for Jun in dorsal closure as well as in the eye, such that jun alleles are NOT lethal. How would you test whether Jun functioned in this process? How would these tests differ from those used by the authors of this paper and the authors of previous papers demonstrating that Jun functions in the eye?