The C. elegans gonadal sheath Sh1 cells extend asymmetrically over a differentiating germ cell population in the proliferative zone

Abstract

The Caenorhabditis elegans adult hermaphrodite germline is surrounded by a thin tube formed by somatic sheath cells that support germ cells as they mature from the stem-like mitotic state through meiosis, gametogenesis, and ovulation. Recently, we discovered that the distal Sh1 sheath cells associate with mitotic germ cells as they exit the niche Gordon et al., 2020. Here, we report that these sheath-associated germ cells differentiate first in animals with temperature-sensitive mutations affecting germ cell state, and stem-like germ cells are maintained distal to the Sh1 boundary. We analyze several markers of the distal sheath, which is best visualized with endogenously tagged membrane proteins, as overexpressed fluorescent proteins fail to localize to distal membrane processes and can cause gonad morphology defects. However, such reagents with highly variable expression can be used to determine the relative positions of the two Sh1 cells, one of which often extends further distal than the other.

Getting there in one piece: The Rac pathway prevents cell fragmentation in a nonprotrusively migrating leader cell during organogenesis

“…Sections of this text are adapted from Li et al, 2022 99 , as they describe our standard laboratory practices.…”

“…Without Rac1 function when cellular cohesion is lost and the cell breaks apart, each fragment can retain leader cell function and support gonad elongation, suggesting that the nucleus is surprisingly dispensable for completion of gonad growth, but is required for long-term maintenance of the stem cell niche. METHODS Sections of this text are adapted from Li et al, 2022 99 , as they describe our standard laboratory practices. Strains Some strains were provided by the CGC, which is funded by NIH Office of Research Infrastructure Programs (P40 OD010440).…”

Higher-order epistasis shapes natural variation in germ stem cell niche activity

“…This is controlled by a network of RNA regulatory proteins, PUF (Pumilio and FBF) RNA-binding proteins, which promote self-renewal downstream GLP-1/Notch, and RNA regulatory pathways (GLD-1, GLD-2, SCF PROM-1 ), which promote entry into meiosis (Chen et al, 2020; Crittenden and Kimble, 2008; Hansen and Schedl, 2013; Haupt et al, 2020; Hubbard and Schedl, 2019; Kimble and Crittenden, 2007). Additional signals from gonadal sheath cells may further modulate C. elegans germ cell proliferation and differentiation (Gopal et al, 2021; Gordon, 2020; Killian and Hubbard, 2005; Li et al, 2022; McCarter et al, 1997; Starich et al, 2014; Tolkin and Hubbard, 2021). Germline PZ cell number is thus determined by the interplay of distal proliferative activity and the spatio-temporal transition into the proximal meiotic state.…”

“…This is controlled by a network of RNA regulatory proteins, including PUF (Pumilio and FBF) RNA-binding proteins that promote self-renewal downstream GLP-1/Notch and other RNA regulatory proteins (GLD-1, GLD-2, SCF ) that promote entry into meiosis 17,37,38,[46][47][48] . Additional signals from gonadal sheath cells further modulate C. elegans germ cell proliferation and differentiation [49][50][51][52][53][54][55] . Germline PZ cell number is thus determined by the interplay of distal proliferative activity and the spatio-temporal transition into the proximal meiotic state.…”