ETS transcription factor pointed controls germline survival in Drosophila

Abstract

Proper gonad development is a pre-requisite for gametogenesis and reproduction. During female gonad formation in Drosophila, the EGF receptor (EGFR) signalling pathway ensures the correct number of primordial germ cells (PGCs) populate the larval gonad. We study the gene pointed (pnt), which acts downstream of the EGFR receptor and belongs to the ETS transcription factor family, with a previously unknown function in gonadogenesis. We report that pnt is expressed in female larval gonads and later in the adult ovarian germline niche and that it is required to sustain proper gametogenesis. Loss of pnt function in female larval gonads, similar to the EGFR, induced PGC overproliferation. Conversely, we isolated a novel mutant allele gene, termed pntaga, which resulted in agametic gonads and ovaries. While pntaga embryos developed gonads containing a normal complement of PGCs, these are subsequently lost by apoptosis during late larval and pupal stages. Molecular characterization of pntaga revealed reduced expression levels of the different pnt isoforms, unveiling a complex autoregulatory network involving the three Pnt proteins. We propose that germline survival in Drosophila gonads requires a precise tuning of EGFR signalling to ensure the appropriate transcriptional activation of its target pnt.