Characterization of Ataxin 2-Binding Protein 1 During Female Germ Cell Differentiation in Drosophila Melanogaster




Yilmaz, Ömür

Journal Title

Journal ISSN

Volume Title


Content Notes


In the Drosophila ovary, the molecules that promote the continued stepwise development of germline stem cells after their exit the niche remain largely unknown. During Drosophila oogenesis, a germline stem cell (GSC) divides asymmetrically to produce a renewing stem cell and a differentiated daughter that will progress through different stages of oogenesis to produce a mature egg. Numerous factors regulate the balance between GSC and a daughter cell, the cystoblast (CB). The Dpp/BMP signaling pathway from the niche silences bam transcription, a key differentiation factor, in the GSC. Bam protein is expressed in the cystoblast and forms a complex with its partner Bgcn, to antagonize the Pumilio-Nanos (Pum-Nos) complex through nos 3’UTR. Repression of Pum-Nos activity by the Bam-Bgcn complex permits CB differentiation. The CB goes through four incomplete divisions to give rise to a 16 cell cyst that buds off from the germarium to form an egg chamber. A number of genes have been found to have roles at 16 cell stage germ cell cysts but the molecular events that govern the intermediate stages (2-, 4- and 8-cell cysts) have remained elusive. In this study, I investigated the function of Drosophila homolog of the human disease gene Ataxin 2-binding protein 1 (A2BP1) during germline cyst differentiation. Through phenotypic analysis I showed that strong A2BP1 mutants display cystic tumors and mitosis to meiosis transition defects while weaker alleles have germline counting defects. Also, by genetic and biochemical analysis, I found that A2BP1 interacts with itself and Bruno, a known translational repressor. In addition, I examined the relationship between A2BP1 protein and other differentiation genes by expression analysis and showed that A2BP1 expression bridges the expression of the early differentiation factor Bam with late markers such as Bruno, Orb and Rbp9. The expression of A2BP1 is lost in bam, snf and mei-P26 mutants but is still present in rbp9 and arrest mutants. These observations might indicate existence of a linear hierarchy between these differentiation genes. In summary, my studies revealed A2BP1 defines a new tier within the genetic hierarchy that promotes the differentiation of single germ cells into mature 16-cell cysts during Drosophila oogenesis.

General Notes

The author has also published articles under the name "Omur Yilmaz Tastan" or "Ömür Yilmaz-Taştan".

Table of Contents


Related URI