Species: other
Mutation name:
type: null mutation
fertility: fertile
Comment: Maternal Larp6 controls oocyte development, chorion formation and elevation. Hau HTA et al. (2020) La-related protein6 (Larp6) is a conserved RNA binding protein found across eukaryotes that has been suggested to regulate collagen biogenesis, muscle development, ciliogenesis and various aspects of cell proliferation and migration. Zebrafish have two Larp6 family genes, larp6a and larp6b In situ hybridisation revealed significant expression of both genes in early embryos, followed by decline of larp6b mRNA by gastrulation stages, whereas larp6a mRNA showed widespread low-level expression throughout the first few days of life. To test the role of Larp6 proteins, genome editing generated predicted nonsense mutations in the first coding exon of each gene, and breeding yielded viable and fertile single and double homozygous mutants. Contrary to expectation, analysis of muscle structure revealed no defects and mutant fish grew and behaved indistinguishably from heterozygous or wild type siblings. No phenotypes similar to collagen or ciliogenesis mutants were observed. Zygotic mutants lacking all wild type Larp6 activity displayed no apparent phenotype and were viable and fertile. However, larp6a mutant females produced defective eggs with chorions that failed to elevate fully and were fragile. Eggs from larp6b single mutant females showed minor chorion defects, but chorions from eggs laid by larp6a;larp6b double mutant females were more defective than those from larp6a single mutant females. Electron microscopy revealed defective chorionogenesis during oocyte development. Nevertheless, maternal zygotic single and double mutants were viable and fertile despite defective chorions and misshapen and constricted early embryogenesis. Mass spectrometry analysis of chorions provided an initial description of chorion protein composition and revealed significant reductions in a subset of zona pellucida and lectin-type proteins between wild type and mutant chorions that paralleled the severity of the phenotype. We conclude that Larp6 proteins are required for normal oocyte development, chorion formation and egg activation.//////////////////