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Open Access Research article

FLI-1 Flightless-1 and LET-60 Ras control germ line morphogenesis in C. elegans

Jiamiao Lu12, William L Dentler1 and Erik A Lundquist1*

Author affiliations

1 Department of Molecular Biosciences, The University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA

2 Current address : Stanford University School of Medicine, Departments of Pediatrics and Genetics, 300 Pasteur Drive, Room H310, Stanford, CA 94305-5208, USA

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Citation and License

BMC Developmental Biology 2008, 8:54  doi:10.1186/1471-213X-8-54

Published: 16 May 2008

Abstract

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

    g
erm
    l
ine
    m
orphogenesis (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.

Conclusion

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.