Nematode genome sequence dramatically extends the nuclear receptor superfamily

Nuclear receptors represent a large class of ligand-activated transcription al regulators; about 70 members of-this protein family have been cloned fro m mammalian or insect species. Thus, it came as a great surprise when the r ecent completion of the Caenorhabditis elegans genome revealed at least 228 genes for nuclear receptors. Clearly, some of these receptors are homologu es of known receptors, but most lack homologues in other species. Whether t hese receptors possess homologues in mammalian species is of great interest ; if these do exist the size of the nuclear receptor superfamily could also expand dramatically in humans.