The Exocyst Component Sec3 Controls Egg Chamber Development Through Notch During Drosophila Oogenesis

Abstract

The exocyst complex plays multiple roles via tethering secretory or recycling vesicles to the plasma membrane. Previous studies have demonstrated that the exocyst contains eight components, which possibly have some redundant but distinct functions. It is therefore interesting to investigate the biological function of each component. Here, we found that Sec3, one component of exocyst complex, is involved in Drosophila egg chamber development. Loss of sec3 results in egg chamber fusion through the abolishment of cell differentiation. In addition, loss of sec3 increases cell numbers but decreases cell size. These defects phenocopy Notch pathway inactivation. In line with this, loss of sec3 indeed leads to Notch protein accumulation, suggesting that the loss of Sec3 inhibits the delivery of Notch onto the plasma membrane and accumulates inactive Notch in the cytoplasm. Loss of sec3 also leads to the ectopic expression of two Notch pathway target genes, Cut and FasciclinIII, which should normally be downregulated by Notch. Altogether, our study revealed that Sec3 governs egg chamber development through the regulation of Notch, and provides fresh insights into the regulation of oogenesis.

EXOC1 plays an integral role in spermatogonia pseudopod elongation and spermatocyte stable syncytium formation in mice

“…Although studies using gene-deficient mouse models have shown that the exocyst is important for embryo development ( Mizuno et al, 2015 ; Friedrich et al, 1997 ; Fogelgren et al, 2015 ; Dickinson et al, 2016 ), its tissue-specific functions in adults are largely unknown. In Drosophila models, the exocyst plays an important role in the formation of both female and male gametes ( Giansanti et al, 2015 ; Wan et al, 2019 ; Murthy and Schwarz, 2004 ; Mao et al, 2019 ). In mice, all exocyst subunits are expressed in male germ cells at each stage of differentiation ( Green et al, 2018 ), and although it is predicted that these subunits may be involved in mammalian spermatogenesis, the function of these subunits is completely unknown.…”

Mutations in the exocyst component EXOC2 cause severe defects in human brain development

“…Remarkably, however, mutations in some subunits are tolerated. Budding yeast can survive LoF mutations of EXOC1 ( Finger and Novick, 1997 ; Novick et al, 1980 ), for example, and in Drosophila, a truncation mutant of EXOC2 that retains the CorEx motif allows organismal viability ( Sommer et al, 2005 ; Wan et al, 2019 ). Exocyst function is also important for proper delivery to the primary cilium of the Joubert syndrome protein Arl13b and for ciliogenesis in a wide range of cell and tissue types.…”