CHARACTERIZATION OF GENES ENCODING MEMBERS OF THE NUCLEAR HORMONE-RECEPTOR SUPERFAMILY FROM ONCHOCERCA-VOLVULUS

Several lines of evidence suggest that molting in parasitic nematodes is controlled through the action of steroid molting hormones, or ecdys ones. In other organisms, the central mediator of steroid hormone acti on is the hormone receptor. These receptor molecules are members of a superfamily of proteins called the nuclear hormone receptor family. Us ing an oligonucleotide derived from the amino-acid sequence of the Dro sophila melanogaster ecdysone receptor, genes encoding homologues of t he nuclear hormone receptor family were identified in the genome of th e human filarial parasite Onchocerca volvulus. The O. volvulus genome contains at least three genes that encode putative members of the nucl ear hormone receptor superfamily. A complete cDNA for one of these gen es, designated OVNHR-1, has been isolated and characterized. The OvNHR -1 cDNA was 2378 bp in length, and contained a single open reading fra me of 1104 bp. The open reading frame encoded a peptide with all of th e features characteristic of a member of the nuclear hormone receptor superfamily of proteins. OVNHR-1 appeared to be encoded by a single-co py gene. Expression of the mRNA corresponding to OvNHR-1 was developme ntally regulated, with maximal expression occurring during early embry ogenesis. The polypeptide encoded by the OVNHR-1 open reading frame is antigenic in a minority of individuals exposed to O. volvulus.