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Genetics, Vol. 178, 1973-1987, April 2008, Copyright © 2008
doi:10.1534/genetics.107.083469
Genetic Analysis of the Caenorhabditis elegans GLH Family of P-Granule Proteins
Caroline Spike*,1,2,
Nicole Meyer*,1,
Erica Racen
,
April Orsborn,3,
Jay Kirchner*,4,
Kathleen Kuznicki,5,
Christopher Yee,6,
Karen Bennett and
Susan Strome*,7
* Department of Biology, Indiana University, Bloomington, Indiana 47405 and Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, Missouri 65212
7 Corresponding author: MCD Biology, Sinsheimer 328, University of California, 1156 High St., Santa Cruz, CA 95064.
E-mail: strome{at}biology.ucsc.edu
The Vasa DEAD-box helicases are widespread markers of germ cells across species, and in some organisms have been shown to be essential for germ-cell formation and development. In contrast to the single Vasa gene in most systems analyzed, Caenorhabditis elegans has four Vasa family members, the germline helicases GLH-1, GLH-2, GLH-3, and GLH-4. Our analysis of deletion alleles of each glh gene demonstrates that GLH-1 is the key member of the family: loss of GLH-1 function causes sterility that is mainly maternal effect, is manifested predominantly at elevated temperature, and is due to reduced germ-cell proliferation and impaired formation of both sperm and oocytes. The other GLHs are not essential. However, GLH-4 serves redundant roles with GLH-1: loss of both genes' function causes glh-1-like sterility at all temperatures. Molecular epistasis analysis demonstrates that GLH-1 and GLH-4 are required for proper association of the PGL family of proteins with P granules, suggesting a pathway of P-granule assembly in which the GLHs are upstream of the PGL proteins and the mRNA cap-binding protein IFE-1. While loss of some P-granule components causes worms to be defective in RNA interference, loss of GLH-1 and GLH-4 does not compromise RNAi. Thus, RNAi likely does not require intact P granules but instead relies on particular P-granule factors. We discuss the evolution of the Vasa/GLH genes and current views of their functions and the assembly and roles of germ granules among species.
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Genetics 2008 178: NP.