CLONING OF A NOVEL ORPHAN RECEPTOR (GCNF) EXPRESSED DURING GERM-CELL DEVELOPMENT

We have cloned a novel member of the nuclear receptor superfamily that has been identified from complementary DNA libraries derived from mou se tissues using a low stringency cross hybridization strategy. The de duced protein sequence contains 495 amino acids and consists of the ch aracteristic DNA-binding and ligand-binding domains of the nuclear rec eptor superfamily. The primary sequence of this new orphan is distinct from those of previously cloned members and subgroups. Analysis of th e DNA-binding properties of the in vitro synthesized protein revealed that this new orphan receptor binds to the sequence TCAAGGTCA that inc ludes the steroidogenic factor-1 half-site and direct repeat with 0 bp spacing elements. Northern blot and ribonuclease protection assays sh owed that the receptor was predominantly expressed in the testis. Resu lts from in situ hybridization experiments confirmed this observation and showed it to be located in the spermatogenic cells. High level exp ression was also detected in developing oocytes in the ovary. Thus, hi gh level expression of this gene is restricted to developing germ cell s, the oocytes and spermatogenic cells. We speculate that this orphan receptor may be a molecule involved in regulating some aspect of meios is, and that the major function of this factor is likely to be involve d in the regulation of gene expression in germ cell development during gametogenesis. It has been designated germ cell nuclear factor.