Role of Phospholipase C in Primordial Germ Cell Migration in Drosophila

Primordial Germ Cells (PGCs) are essential for fertility and the preservation of the species. Across the animal kingdom, PGCs are specified early in embryonic development and must migrate to reach the somatic gonad. In common PGC migration models, Zebrafish and Drosophila, migrating PGCs exhibit calcium (Ca2+) bursts. Despite this broadly shared feature, the source and function of Ca2+ dynamics in PGC development is unclear. We use the Drosophila melanogaster model, which has many advanced genetic and live imaging tools. To understand the source and function of Ca2+ signaling, we first targeted Phospholipases C (PLCs), which integrate signals downstream of G protein-coupled receptors and receptor tyrosine kinases, leading to either the release of Ca2+ from the endoplasmic reticulum or an influx of Ca2+ from the extracellular environment. Fortunately, the Drosophila genome contains only one RTK-like PLC and two GPCR-linked PLCs. We tested the genetic requirements of all three PLCs, and found that only the GPCR-linked Phospholipase C 21 c (plc21c) is required for PGC development in Drosophila. As our genetic studies involved ubiquitous loss of plc21c, we next tested whether plc21c is required in the surrounding somatic cells. To this end, we crossed virgin females carrying the mesodermal driver twi-GAL4; 24B-GAL4 against three plc21c RNAi lines to knock down plc21c mRNA. Quantification of extragonadal PGCs revealed no statistical significance between mesodermal depletion of plc21c and controls. These data are consistent with our hypothesis that plc21c and Ca2+ signaling are autonomously required in migrating PGCs for proper gonad colonization. We will further test our hypothesis that plc21c is required only in PGCs by ex vivo migration assay using sorted PGCs and genetic interactions assays between plc21c and guidance cues. Results from this study will help us understand the function of Ca2+ signaling requirements in PGC migration. This work was supported by R00HD097306 from NICHD, as well as start-up funds from UTSA and a GREAT seed grant from UTSA for LJB.