Drosophila pericentrin‐like protein promotes the formation of primordial germ cells

Abstract

Summary Primordial germ cells (PGCs) are the precursors to the adult germline stem cells that are set aside early during embryogenesis and specified through the inheritance of the germ plasm, which contains the mRNAs and proteins that function as the germline fate determinants. In Drosophila melanogaster, formation of the PGCs requires the microtubule and actin cytoskeletal networks to actively segregate the germ plasm from the soma and physically construct the pole buds (PBs) that protrude from the posterior cortex. Of emerging importance is the central role of centrosomes in the coordination of microtubule dynamics and actin organization to promote PGC development. We previously identified a requirement for the centrosome protein Centrosomin (Cnn) in PGC formation. Cnn interacts directly with Pericentrin‐like protein (PLP) to form a centrosome scaffold structure required for pericentriolar material recruitment and organization. In this study, we identify a role for PLP at several discrete steps during PGC development. We find PLP functions in segregating the germ plasm from the soma by regulating microtubule organization and centrosome separation. These activities further contribute to promoting PB protrusion and facilitating the distribution of germ plasm in proliferating PGCs.

Orb-dependent polyadenylation contributes to PLP expression and centrosome scaffold assembly

“…In control embryos, Cnn radiates symmetrically from centrosomes, forming interphase-specific flares, as previously described (Figure 4C, WT) (Megraw et al, 2002). Consistent with our prior work, Cnn distribution appears severely disorganized in plp embryos with fragmented Cnn flares and Cnn puncta dispersed within the cytosol (Figure 4C, plp) (Lerit et al, 2015;Fang and Lerit, 2020). Quantification of the relative number of cytoplasmic Cnn puncta in segmented images shows a significant, nearly 6-fold increase in Cnn puncta in plp embryos, as compared to WT (Figure 4D).…”

“…In orb mutant embryos, we observed PLP protein is ~50% downregulated (Figure 3A, E). We recently showed plp hemizygote embryos (plp 2172 /+) also result in an average ~50% downregulation of PLP protein (Fang and Lerit, 2020). Therefore, we generated plp 2172 , orb F343 recombinant chromosomes and crossed these animals to orb mel mutants to harvest embryos from plp hemizygous, orb mutant mothers (genotype: plp 2172 /+, orb F343 /orb mel ; hereafter, plp/+, orb).…”

A study of the expression of germline-specific paralogs of the ubiquitously expressed NAC complex revealed their association with centrosomes

“…The presence of gNAC in the cytoplasm of pole cells has been expected, it was also preserved in the centrosomes of pole cells, the precursors of germ cells. It has been reported that the centrosome proteins participate in the organization and development of the primordial germ cells (Fang and Lerit, 2020) and centrosome nucleated microtubules facilitate germ plasm partitioning between proliferating primordial germ cells, which are highly sensitive to the dosage of germ plasm components (Lerit and Gavis, 2011).…”

“…It was found that both gNAC and the germinal marker, the VASA protein, can be detected in the cytoplasm of primordial germ cells and their precursors migrating to the sites of gonad formation. The importance of the presence of gNAC in embryonic syncytial centrosomes is highlighted by recent results revealing the critical role of centrosomes in the development of pole buds and pole cells and the formation of microtubules involved in the proper distribution of germplasm components in primordial germ cells (Lerit and Gavis, 2011; Fang and Lerit, 2020) and in protein interactions (Nishi et al, 2014; Koike et al, 2020; Rieloff and Skepo, 2020). We speculate that these events may be closely supported by a specific germline proteostasis network involving gNACs as internally disordered proteins carrying phosphosites.…”

The PCM scaffold enables RNA localization to centrosomes

“…Human PCNT and Drosophila Pcnt-like protein (Plp) share functionally conserved roles in PCM scaffolding and microtubule nucleation [23][24][25][26][27][28]. In humans, loss-of-function PCNT mutations are associated with microcephalic osteodysplastic primordial dwarfism type II (MOPD II), as well as cardiac and neurovascular abnormalities [29][30][31][32][33].…”