GSP-2/PP1 phosphatase and small RNAs promote germ cell immortality and P-granule maintenance

Germ cell immortality can be promoted by small RNA-mediated nuclear silencing. We identified a hypomorphic mutation in gsp-2, a PP1/Glc7 phosphatase, that compromised germ cell immortality. C. elegans GSP-2 is recruited by LAB-1 to long arms of meiotic chromosomes, and loss of LAB-1 causes a Mrt phenotype. This implies that a meiotic chromosome cohesion function of GSP-2 may promote germ cell immortality, revealing the first meiotic process that promotes germ cell immortality. Histone H3 phosphorylation was upregulated in oocytes of gsp-2 phosphatase and small RNA silencing mutants suggesting that GSP-2 may modify histones in the context of small RNA-mediated genomic silencing. Germline degeneration, univalents and loss of P-granules were observed for gsp-2 and small RNA genomic silencing mutants at sterility. Moreover, P-granule dysfunction was sufficient to induce sterility, germline atrophy and univalents, implying that altered germ granule function may correspond to the stress that elicits transgenerational sterility of small RNA genome silencing mutants.