The novel isoform of the progesterone receptor cDNA in the human testis and detection of its mRNA in the human uterine endometrium

A novel isoform (termed isoform S) of the progesterone receptor (PR) cDNA (PR isoform S cDNA) which consists of a previously unidentified 5’ sequence and exons 4–8 of the intracellular PR gene has been cloned from the human testicular cDNA library. The 5′ sequence of the message was confirmed to be derived from a novel exon (termed exon S) by genomic cloning. The expression level of the PR isoform S mRNA was higher in the spermatozoon than in the uterine endometrium with a lower expression level of the PR isoforms B and A mRNAs in the spermatozoon than in the endometrium. These results implied that the PR isoform S which was possibly translated from the PR isoform S mRNA in the spermatozoon might be related to the cell surface membrane PR. Moreover, the PR isoform S in the uterine endometium might play some physiological and/or pathogenic roles.