title: MSP and GLP-1/Notch signaling coordinately regulate actomyosin-dependent cytoplasmic streaming and oocyte growth in C. elegans.
abstract: Fertility depends on germline stem cell proliferation, meiosis and gametogenesis, yet how these key transitions are coordinated is unclear. In C. elegans, we show that GLP-1/Notch signaling functions in the germline to modulate oocyte growth when sperm are available for fertilization and the major sperm protein (MSP) hormone is present. Reduction-of-function mutations in glp-1 cause oocytes to grow abnormally large when MSP is present and Galpha(s)-adenylate cyclase signaling in the gonadal sheath cells is active. By contrast, gain-of-function glp-1 mutations lead to the production of small oocytes. Surprisingly, proper oocyte growth depends on distal tip cell signaling involving the redundant function of GLP-1 ligands LAG-2 and APX-1. GLP-1 signaling also affects two cellular oocyte growth processes, actomyosin-dependent cytoplasmic streaming and oocyte cellularization. glp-1 reduction-of-function mutants exhibit elevated rates of cytoplasmic streaming and delayed cellularization. GLP-1 signaling in oocyte growth depends in part on the downstream function of the FBF-1/2 PUF RNA-binding proteins. Furthermore, abnormal oocyte growth in glp-1 mutants, but not the inappropriate differentiation of germline stem cells, requires the function of the cell death pathway. The data support a model in which GLP-1 function in MSP-dependent oocyte growth is separable from its role in the proliferation versus meiotic entry decision. Thus, two major germline signaling centers, distal GLP-1 activation and proximal MSP signaling, coordinate several spatially and temporally distinct processes by which germline stem cells differentiate into functional oocytes.
authors.affiliation: Department of Genetics, Cell Biology and Development, University of Minnesota, 6-160 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, USA.
authors.forename: Saravanapriah
authors.initials: S
authors.lastname: Nadarajan
authors.forename: J Amaranath
authors.initials: JA
authors.lastname: Govindan
authors.forename: Marie
authors.initials: M
authors.lastname: McGovern
authors.forename: E Jane Albert
authors.initials: EJ
authors.lastname: Hubbard
authors.forename: David
authors.initials: D
authors.lastname: Greenstein
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D017173:Caenorhabditis elegans / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D003595:Cytoplasmic Streaming / Q000502:physiology*; D017930:Genes, Reporter; D015801:Helminth Proteins / Q000235:genetics / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism; D009865:Oocytes / Q000166:cytology / Q000502:physiology*; D051880:Receptors, Notch / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D000199:Actins; D029742:Caenorhabditis elegans Proteins; C060620:Glp-1 protein, C elegans; D015801:Helminth Proteins; D008562:Membrane Glycoproteins; D051880:Receptors, Notch; C050602:major sperm protein, nematode; D009218:Myosins