Critical Role of Caenorhabditis elegansHomologs of Cds1 (Chk2)-Related Kinases in Meiotic Recombination

Although chromosomal segregation at meiosis I is the critical process for genetic reassortment and inheritance, little is known about molecules involved in this process in metazoa. Here we show by utilizing doublestranded RNA (dsRNA)-mediated genetic interference that novel protein kinases (Ce-CDS-1 and Ce-CDS-2) related to Cds1 (Chk2) play an essential role in meiotic recombination in Caenorhabditis elegans. Injection of dsRNA into adult animals resulted in the inhibition of meiotic crossing over and induced the loss of chiasmata at diakinesis in oocytes of F1 animals. However, electron microscopic analysis revealed that synaptonemal complex formation in pachytene nuclei of the same progeny of injected animals appeared to be normal. Thus, Ce-CDS-1 and Ce-CDS-2 are the first example of Cds1-related kinases that are required for meiotic recombination in multicellular organisms. Protein kinases play crucial roles in the regulation of a wide variety of cellular functions. A novel family of protein kinases, bearing a phosphospecific protein-protein interaction motif, the forkhead-associated (FHA) domain (11), has been identified and shown to be involved in checkpoint regulation and DNA repair induced by DNA damage (16). Protein kinases belonging to this family include Saccharomyces cerevisiae Rad53, Dun1, and Mek1p (MRE4), Schizosaccharomyces pombe Cds1