DEAD box RNA helicases are involved in diverse cellular functions such as RNA splicing, ribosome assembly, initiation of translation, gametogenesis, embryogenesis, and cell growth. Several C. elegans RNA helicases have been identified to be components of P granules (mRNA-protein complexes that are present in the germline and that are also essential for its function). VASA is the first RNA helicase described as a Drosophila polar granule component, and is essential in the female germline. Based on interactions between VASA and translation factors it has been suggested that this protein might be involved in translational regulation; however, its function remains to be elucidated. In the C. elegans genome, the ORF most closely related to Drosophila vasa is Y54E10A.9. This gene is comparably similar to another RNA helicase from Drosophila known as belle. Belle is expressed in female and male somatic and germline tissues, and is required for oogenesis (1). Based on this homology, we have named Y54E10A.9 vasa belle like helicase,
vbh-1. Using RNAi, we have found that
vbh-1 is essential for germline function in C. elegans. Nearly half of the
vbh-1(RNAi) F1 hermaphrodites are sterile, and the remainder show dramatically reduced brood size and produce a high percentage of sterile progeny.
vbh-1(RNAi) F1 hermaphrodite gonads are characterized by normal germ cell numbers and size, but produce a reduced number of sperm. In many of these animals, the most proximal oocytes contain endomitotic nuclei.
vbh-1(RNAi) males are also sterile. Antibody staining experiments have shown that the VBH-1 protein is present in both the male and hermaphrodite germline. VBH-1 is found in the germ cell cytoplasm, and is abundant in P granules in both hermaphodites and males. We have been unable to detected VBH-1 staining in the somatic gonad or other tissues, suggesting that this protein might be germline specific. We are continuing to analyze the
vbh-1(RNAi) phenotype, and investigate VBH-1 function.Reference1. Johnstone, O., Deuring, R., Fuller, M.T. and Lasko, P. Bel is an essential DEAD-box protein with a requirement in the germline. A. Dros. Res. Conf. 2001:63A