miR-23a2 ensures germline expansion through post-transcriptional regulation of proliferation
The establishment of an adequate pool of embryonic germ cells is a prerequisite for fertility, but the molecular factors controlling their expansion are not fully understood. In this study, we show that the conserved microRNA miR-23a2 is required for proper cystic proliferation in the germline of the medaka fish (Oryzias latipes). Disruption of miR-23a2 results in the de-repression of ndrg1b, a factor known to inhibit proliferation, which leads to fewer germ cells and disorganized cellular cysts. Transcriptomic analyses further revealed changes in pathways associated not only with the cell cycle but also with immune responses and extracellular matrix organization. Together, these findings indicate that miR-23a2 coordinates proliferative activity with tissue architecture and homeostatic cues. By uncovering this previously unrecognized layer of microRNA regulation, our work highlights how small RNAs contribute to securing reproductive success in vertebrates.