FLI-1 Flightless-1 and LET-60 Ras control germ line morphogenesis in C. elegans.
BACKGROUND
In the C. elegans germ line, syncytial germ line nuclei are arranged at the cortex of the germ line as they exit mitosis and enter meiosis, forming a nucleus-free core of germ line cytoplasm called the rachis. Molecular mechanisms of rachis formation and germ line organization are not well understood.


RESULTS
Mutations in the fli-1 gene disrupt rachis organization without affecting meiotic differentiation, a phenotype in C. elegans referred to here as the germ line morphogenesis (Glm) phenotype. In fli-1 mutants, chains of meiotic germ nuclei spanned the rachis and were partially enveloped by invaginations of germ line plasma membrane, similar to nuclei at the cortex. Extensions of the somatic sheath cells that surround the germ line protruded deep inside the rachis and were associated with displaced nuclei in fli-1 mutants. fli-1 encodes a molecule with leucine-rich repeats and gelsolin repeats similar to Drosophila flightless 1 and human Fliih, which have been shown to act as cytoplasmic actin regulators as well as nuclear transcriptional regulators. Mutations in let-60 Ras, previously implicated in germ line development, were found to cause the Glm phenotype. Constitutively-active LET-60 partially rescued the fli-1 Glm phenotype, suggesting that LET-60 Ras and FLI-1 might act together to control germ line morphogenesis.


CONCLUSIONS
FLI-1 controls germ line morphogenesis and rachis organization, a process about which little is known at the molecular level. The LET-60 Ras GTPase might act with FLI-1 to control germ line morphogenesis.
Lu
Jiamiao
J
Department of Molecular Biosciences, The University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA. jiamiao@stanford.edu
Dentler
William L
WL
Lundquist
Erik A
EA
D000199:Actins / Q000378:metabolism; D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000235:genetics* / Q000378:metabolism; D018628:Gene Dosage; D018507:Gene Expression Regulation, Developmental; D018095:Germ-Line Mutation; D006066:Gonads / Q000378:metabolism; D008840:Microfilament Proteins / Q000235:genetics* / Q000378:metabolism; D009024:Morphogenesis / Q000235:genetics*; D010641:Phenotype; D017384:Sequence Deletion; D018631:ras Proteins / Q000235:genetics* / Q000378:metabolism
D000199:Actins; D029742:Caenorhabditis elegans Proteins; D008840:Microfilament Proteins; C528409:fli-1 protein, C elegans; C066646:let-60 protein, C elegans; D018631:ras Proteins