Niche Cell Wrapping Ensures Primordial Germ Cell Quiescence and Protection from Intercellular Cannibalism

Abstract

Highlights d Niche cell wrapping templates a laminin-based basement membrane around the gonad d Basement membrane and dystroglycan maintain niche cell wrapping d Basement membrane inhibits Notch to ensure primordial germ cell quiescence d Niche cell wrapping protects primordial germ cells from cannibalism by neighboring cells

DAF-18/PTEN inhibits germline zygotic gene activation during primordial germ cell quiescence

“…However, this phenotype does not likely relate to DAF-18 since, unlike PGC divisions in the daf-18 mutant [5], loss of akt-1 does not suppress PGC divisions that occur upon depletion of laminin. Rather, inappropriate PGC divisions are dependent on GLP-1 Notch signaling [71]. We examined our RNA-seq dataset and found that both sygl-1 and lst-1 (the relevant outputs of GLP-1 signaling) are indeed detected but their levels are not significantly different in starved daf-18 mutants versus wild type.…”

“…However, these divisions likely reflect defects in fate specification [65] rather than alterations in levels of germline transcripts. In addition, depletion of the basement membrane component laminin allows PGCs to divide [71]. However, this phenotype does not likely relate to DAF-18 since, unlike PGC divisions in the daf-18 mutant [5], loss of akt-1 does not suppress PGC divisions that occur upon depletion of laminin.…”

Notch pathway is required for protection against heat-stress in spermatogonial stem cells

“…During embryogenesis, the constitutive activation of NOTCH1 signaling in Sertoli cells caused the exit of gonocyte from the quiescence status [26]. In flies, Notch signaling directly controls germline stem cell development and maintenance [5,63], reinforcing the importance of cell-to-cell Notch signaling in the regulation of germ cell differentiation. Interestingly, although our results in medaka support the activation of the Notch pathway, including receptors, ligands, γ-secretase and the respective effectors of this pathway, the activation of Notch signals seems to work in the opposite direction to that described above, wherein the input signal (high temperature) seems to be sensed by SGa while the output seems to be in the somatic cells with a high expression of Pen-2, presumably Sertoli cells [44].…”

“…In this sense, despite countless studies, it is still difficult to characterize the somatic stem niche in v e r t e b r a t e s [ 1 7 ] . R e c e n t s t u d i e s i n e a r l y development of mice have been able to show a possible somatic stem niche [18], and much progress has also been made in other model organisms, like flies [5,6]. In both cases, it was observed that one of the main signaling pathways involved is the Notch pathway.…”

“…Spermatogenesis is a cellular process necessary for the formation of male gametes from spermatogonial stem cells (SSCs), which proliferate synchronically and differentiate into millions of spermatozoa (SZ) or are constantly self-renewed asynchronically, like other stem cells [1,2]. To maintain continuous spermatogenesis throughout the male reproductive life, SSCs reside in the "niche", a specialized microenvironment of the testes, which regulates their properties of self-renewal, pluripotency, quiescence, size, and their ability to differentiate and proliferate [3][4][5][6]. This ability of the niche to maintain SSCs homeostasis is what allows them to survive under adverse conditions.…”