RTR: a new member of the nuclear receptor superfamily that is highly expressed in murine testis.

We have identified and cloned a novel member of the nuclear receptor superfamily from murine testis, referred to as retinoid receptor-related testis-associated receptor or RTR. Degenerate PCR primers homologous to two conserved regions of the DNA-binding domain of members of this superfamily were employed to identify this gene. The amino-acid sequence of RTR is most closely related to that of the mouse RXRs with an overall identity of 32-34%; the highest similarity (61%) is observed in the DNA-binding domain. Northern blot analysis using RNA from multiple tissues showed that RTR is predominantly expressed in the testis. Northern blot analysis using RNA from different testicular cell types showed that RTR mRNA is not expressed in early germ cells or Sertoli cells but is most abundant in round spermatids. Our observations suggest that this putative transcription factor plays a role in the regulation of gene expression particularly during the post-meiotic phase of spermatogenesis.