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. Author manuscript; available in PMC: 2022 Mar 1.
Published in final edited form as: Wiley Interdiscip Rev RNA. 2020 Aug 1;12(2):e1620. doi: 10.1002/wrna.1620

Figure 6. Brat and Mei-P26 regulate Drosophila oogenesis.

Figure 6.

A. Early oogenesis in adult Drosophila. Germline Stem Cells (GSCs), in contact with somatic cap cells, receive Decapentaplegic (Dpp) signal that is necessary for their maintenance. The resulting signaling cascade ensures expression of Nanos (N), Pumilio (P), and Mei-P26 (M). Asymmetric cell division pushes one daughter cell below the signal threshold (dashed line), causing expression of Bam (B) and Brat. The nascent cystoblast (CB) further divides incompletely into cysts, one of which is designated to become the oocyte (Ooc).

B. Molecular pathways maintaining GSC identity. Dpp signaling promotes Mothers against Dpp (Mad)-mediated transcriptional (Tx) regulation of Bag of marbles (bam). At the same time, Nanos (Nos), Pum, and Mei-P26 repress translation (TL) of brat mRNA.

C. Molecular pathways promoting differentiation of nascent cystoblasts. Loss of Dpp signal in the cystoblast allows expression of Bam. In turn, Bam collaborates with Mei-P26, Sex-lethal (Sxl), and benign gonial cell neoplasm (Bgcn) proteins to repress translation of Nanos mRNA. As a result, translational repression of Brat is alleviated. Brat protein collaborates with Pum to repress expression of mad, medea, and schnurri (shn) transcription factors. Dotted lines represent reduced strength of interactions.