title: CSR-1 and P granules suppress sperm-specific transcription in the C. elegans germline.
abstract: Germ granules (P granules) in C. elegans are required for fertility and function to maintain germ cell identity and pluripotency. Sterility in the absence of P granules is often accompanied by the misexpression of soma-specific proteins and the initiation of somatic differentiation in germ cells. To investigate whether this is caused by the accumulation of somatic transcripts, we performed mRNA-seq on dissected germlines with and without P granules. Strikingly, we found that somatic transcripts do not increase in the young adult germline when P granules are impaired. Instead, we found that impairing P granules causes sperm-specific mRNAs to become highly overexpressed. This includes the accumulation of major sperm protein (MSP) transcripts in germ cells, a phenotype that is suppressed by feminization of the germline. A core component of P granules, the endo-siRNA-binding Argonaute protein CSR-1, has recently been ascribed with the ability to license transcripts for germline expression. However, impairing CSR-1 has very little effect on the accumulation of its mRNA targets. Instead, we found that CSR-1 functions with P granules to prevent MSP and sperm-specific mRNAs from being transcribed in the hermaphrodite germline. These findings suggest that P granules protect germline integrity through two different mechanisms, by (1) preventing the inappropriate expression of somatic proteins at the level of translational regulation, and by (2) functioning with CSR-1 to limit the domain of sperm-specific expression at the level of transcription.
authors.affiliation: Kathryn W. Davis Center for Regenerative Biology and Medicine, Mount Desert Island Biological Laboratory, Bar Harbor, ME 04672, USA.
authors.forename: Anne C
authors.initials: AC
authors.lastname: Campbell
authors.affiliation: Kathryn W. Davis Center for Regenerative Biology and Medicine, Mount Desert Island Biological Laboratory, Bar Harbor, ME 04672, USA dupdike@mdibl.org.
authors.forename: Dustin L
authors.initials: DL
authors.lastname: Updike
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D005854:Germ Cells / Q000502:physiology*; D008297:Male; D034622:RNA Interference / Q000502:physiology; D013091:Spermatogenesis / Q000235:genetics / Q000502:physiology; D013094:Spermatozoa / Q000378:metabolism*
chemical_list: D029742:Caenorhabditis elegans Proteins
keywords: C. elegans; CSR-1; Germ granules; Germline; Germline sex determination; P granules; Sperm; Spermatogenesis