Germline-Soma Dychotomy

The entire Drosophila embryo initially develops as a syncytium of synchronously dividing nuclei.  However, when a subset of these nuclei reaches the germ plasm, they become surrounded by cell membranes. The mechanism of PGC cell formation is strikingly different from the process that controls somatic cells:  PGC formation relies solely on maternal factors and occurs 1.5 hours and four nuclear divisions earlier than somatic cellularization, which relies on specific factors synthesized by the zygote.  Using high-resolution live-imaging, we determined that PGCs form via two constrictions: one, the “bud neck constriction”, separates a budding nucleus basally from the rest of the embryo, while a second constriction, the cytokinetic furrow, separates the dividing nucleus along the anaphase furrow into two cells. The bud neck constriction is unusual as it occurs even after inhibition of microtubules and thus independent of the triggers that activates anaphase restriction. We found that the maternally supplied Germ Cell-less (GCL) protein is an instructive and rate-limiting component of bud-neck constriction. GCL encodes a conserved BTB protein and we are studying its mechanism of action at the genetic and biochemical level.







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