The protein encoded by the open reading frame F08b4.1 is homologous to human DICE-1 protein, which was first identified in a human lung carcinoma cell as a candidate tumor suppressor. Although human DICE-1 (deleted in cancer 1) is presumed to be a tumor suppressor, its detailed molecular function is unknown. We have examined the functions and expression pattern of Ce-DIC-1 by RNA interference and immunostaining. Ce-DIC-1 was localized by immunostaining in the endoplasmic reticulum (ER) of germ cells from the pachytene stage, oocytes, and embryonic cells. RNAi of the
Ce-dic-1 expression at the young adult stage resulted in complete embryonic lethality. When RNAi was performed from the L1 stage, pleiotropic phenotypes in the germ line such as undersized gonads, abnormal gonad migration, defective oocyte development, endomitotic oocytes, increased apoptosis, and protruding vulva appeared.
dic-1(RNAi) embryos showed increased number of cell corpses and morphological defects, followed by developmental arrests at a late embryonic stage. The morphological defects induced by RNAi of
dic-1 were observed in pharynx, gut, hypodermis, and muscle using several GFP-expressing strains. These RNAi phenotypes showed that the Ce-DIC-1 is required for oocyte formation and embryonic morphogenesis in Caenorhabditis elegans. Especially, increased apoptosis by the RNAi together with the intracellular localization in ER suggest the possibility that the DIC-1 protein may be involved in the regulation of apoptosis.