Semenogelin I and II, the predominant human seminal plasma proteins, are also expressed in non-genital tissues.

Semenogelin I (SgI) and semenogelin II (SgII) are the dominating protein components of the coagulum formed by freshly ejaculated human semen. The primary source of these proteins is the seminal vesicles and, apart from a small production of SgII in epididymis, they have not been detected in other tissues. In this report, we have re-examined the distribution of SgI and SgII transcripts and protein by RT-PCR and immunohistochemistry. Both SgI and SgII transcripts were demonstrated in several tissues, with the strongest signals coming from seminal vesicles, vas deferens, prostate, epididymis and trachea. Transcripts in the gastro-intestinal tract and skeletal muscle almost exclusively encoded SgI, whereas in kidney and testis, SgII transcripts were predominant. By immunohistochemistry, the basal cell layer of the secretory epithelium in prostate, trachea and bronchi was stained by antibodies recognizing both SgI and SgII. This is in contrast to the seminal vesicle and vas deferens, where the luminal cells were stained. The staining of skeletal muscle cells and a few scattered cells in the central nervous system suggests that semenogelin expression is not restricted to epithelial cells.