A novel group of <i>pumilio</i> mutations affects the asymmetric division of germline stem cells in the <i>Drosophila</i> ovary

TLDR

Germline stem cells are essential for gametogenesis, yet their formation, self‑renewal division, and genetic regulation remain poorly understood. The study characterizes the self‑renewing asymmetric division of Drosophila ovarian germline stem cells, identified by the spectrosome marker. We found that mutations in the pumilio locus (ovt) and in piwi disrupt asymmetric division, that spectrosome development tracks GSC lineage, and that post‑transcriptional repression is required for germline stem cell maintenance.

Abstract

Germline stem cells play a pivotal role in gametogenesis; yet little is known about how they are formed, how they divide to self-renew, and how these processes are genetically controlled. Here we describe the self-renewing asymmetric division of germline stem cells in the Drosophila ovarian germline, as marked by the spectrosome, a cytoplasmic structure rich in membrane skeletal proteins. The ontogeny of the spectrosome marks the lineage of germline stem cells. We identified two new groups of mutations in which the divisional asymmetry is disrupted. The first, which we refer to as ovarette (ovt) mutations, was shown to correspond to a novel class of mutations in the pumilio locus. Since pumilio is known to posttranscriptionally repress the expression of target genes at earlier stages of germ cell development, our results suggest that a similar activity is needed to maintain germ line stem cells. We have also identified a second and novel gene, piwi, whose mutations abolish germline stem cell division.