Drosophila Cyclin J is a poorly characterized cell cycle regulator that is expressed in ovaries and early embryos. The Cyclin J gene (CycJ) lies immediately downstream of armitage, a gene involved in RNA interference pathways and required for assembly of RNA induced silencing complexes. Previous studies have shown that a hypomorphic armi mutant leads to DNA damage and checkpoint-dependent defects in oocyte axis specification, but a role for CycJ in oogenesis has not been explored. Here we assessed oogenesis in armi and CycJ null mutants by deleting both genes together and then complementing the double mutant with each gene individually. We show that a null of armi results in not only axis specification defects but also germline stem cell (GSC) depletion. This result is consistent with the established role of other RNA interference pathway members in maintaining GSCs. In contrast, CycJ null mutants displayed no obvious defects in GSC maintenance or axis specification. However, deletion of both armi and CycJ together resulted in a striking up regulation of cystoblast division in the mutant germaria. Ovaries from the double mutant had an excess of cystoblasts at the anterior and abnormal cysts containing multiple clusters of 16 interconnected cystocytes with a single oocyte at the posterior. These cysts were eventually eliminated, rendering the ovarioles agametic. This novel phenotype, unlike that for an armi loss of function, was not suppressed by a mutation in the checkpoint gene, maternal nuclear kinase (mnk). The strong genetic interaction between armi and CycJ reveals a novel role for CycJ in coordinating GSC division and oocyte development.
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|Advisor:||Finley, Russell L., Jr.|
|Commitee:||Akins, Robert, Pile, Lori, VanBerkum, Mark F.A|
|School:||Wayne State University|
|Department:||Biochemistry and Molecular Biology|
|School Location:||United States -- Michigan|
|Source:||DAI-B 70/08, Dissertation Abstracts International|
|Subjects:||Molecular biology, Genetics, Biochemistry|
|Keywords:||Cyclin, Cystoblasts, Germline stem cells, Oogenesis, piRNA|
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