GLD-3 and Control of the Mitosis/Meiosis Decision in the Germline of Caenorhabditis elegans

Abstract

Germ cells can divide mitotically to replenish germline tissue or meiotically to produce gametes. In this article, we report that GLD-3, a Caenorhabditis elegans Bicaudal-C homolog, promotes the transition from mitosis to meiosis together with the GLD-2 poly(A) polymerase. GLD-3 binds GLD-2 via a small N-terminal region present in both GLD-3S and GLD-3L isoforms, and GLD-2 and GLD-3 can be co-immunoprecipitated from worm extracts. The FBF repressor binds specifically to elements in the gld-3S 3Ј-UTR, and FBF regulates gld-3 expression. Furthermore, FBF acts largely upstream of gld-3 in the mitosis/meiosis decision. By contrast, GLD-3 acts upstream of FBF in the sperm/oocyte decision, and GLD-3 protein can antagonize FBF binding to RNA regulatory elements. To address the relative importance of these two regulatory mechanisms in the mitosis/meiosis and sperm/oocyte decisions, we isolated a deletion mutant, gld-3(q741), that removes the FBF-binding site from GLD-3L, but leaves the GLD-2-binding site intact. Animals homozygous for gld-3(q741) enter meiosis, but are feminized. Therefore, GLD-3 promotes meiosis primarily via its interaction with GLD-2, and it promotes spermatogenesis primarily via its interaction with FBF.

mir-35 is involved in intestine cell G1/S transition and germ cell proliferation in C. elegans

“…In the gonad, GLP-1 (abnormal Germ Line Proliferation)/Notch signaling is essential to promote germ line divisions in distal mitotic region [19][20][21][22]. GLD (defective in Germ Line Development) family plays a key role in determining meiosis entry and indirectly regulates mitotic proliferation of the germline [23][24][25][26][27]. We found that mir-35 may down-regulate gld-1 to ensure a normal germline proliferation in distal the mir-35 mutant gk262, less intestinal nuclei were observed than the wide type, at 3-fold and L3/L4 stages, respectively (Table 1, P < 0.001, Student t-test).…”

“…For RNAi experiments in the temperature-sensitive strains, we placed dsRNAs injected worms at 20 °C for 8 h for RNAi to take effect, shifted injected worms to 25 °C and obtained 3-fold embryos (RNAi) developed from laid eggs of RNAi animals. Mutations used in this study were as follows: cdc- 25 The promoter of ges-1 was amplified with the primers 5′ GCG-CATGCTCACCAATACCTTTAGTGAC 3′ and 5′ GGGGATC-CCTGAATTCAAAGATAAGATATGT 3′.…”

Cyclin E and CDK-2 regulate proliferative cell fate and cell cycle progression in the C. elegans germline

“…Another component of the GLD-1 pathway is NOS-3 (Hansen et al, 2004a). The GLD-2 pathway includes the GLD-2 cytoplasmic poly(A) polymerase (Wang et al, 2002) and GLD-3, an RNA-binding protein (Eckmann et al, 2004). It remains unclear how the regulatory activities of these pathways specifically promote the meiotic cell fate.…”

Genetics of germ cell development

“…These proteins inhibit meiotic entry by preventing translation of the meiosis-promoting genes GLD-1, a translational repressor, and GLD-3, a translational activator, that act along with the poly(A) polymerase GLD-2 and the nanos homolog NOS-3 to coordinate meiotic initiation. [57][58][59] GLD-3 and NOS-3 inhibit FBF-1 and FBF-2 function, maintaining the meiotic state once it has been initiated. 60,61 C. elegans hermaphrodites produce male and female gametes sequentially: the first few rounds of meiosis produce SPERMATOCYTES, and the rest of the GSCs then commit to OOCYTE production for the remainder of the animal's life.…”