THE CAENORHABDITIS-ELEGANS ORPHAN NUCLEAR HORMONE-RECEPTOR GENE NHR-2FUNCTIONS IN EARLY EMBRYONIC-DEVELOPMENT

We have identified a Caenorhabditis elegans gene, nhr-2 that is a memb er of the nuclear hormone receptor superfamily of transcription factor s and defines a new subclass of the superfamily. nhr-2 messenger RNA i s expressed in the maternal germline and during the first half of embr yogenesis. Zygotic expression of nhr-2 begins by the 16-cell stage, ma king it one of the earliest genes known to be transcribed in the embry o. Immunolocalization detects NHR-2 protein in embryonic nuclei as ear ly as the 2-cell stage. The protein is present in every nucleus until the 16- to 20-cell stage. Subsequently, expression continues in many, but not all, cell lineages, becoming progressively restricted to the a nterior and dorsal regions of the embryo and disappearing during the i nitial stages of morphogenesis. Disruption of nhr-2 function with anti sense RNA results in embryonic and early larval arrest, indicating tha t the gene has an essential function in embryonic development. nhr-2 d oes not correspond to known mutations mapped to the same genetic inter val, and will provide an entry point for further study of a heretofore uncharacterized zygotic gene regulatory pathway. (C) 1997 Academic Pr ess.