Ejaculates from the common marmoset (Callithrix jacchus) contain semenogelin and beta-microseminoprotein but not...

Human seminal plasma contains high concentrations of prostatic acid phosphatase (PAP), prostate-specific antigen (PSA), beta-microseminoprotein (MSP), semenogelin I (SgI), and semenogelin II (SgII), whereas only PAP and MSP are present in rodents. In order to gain a better understanding of the evolution and function of semen proteins, we have studied ejaculates from the common marmoset (Callithrix jacchus)-a New World monkey. Semen samples were analyzed with SDS-PAGE, Western blotting, and isoelectric focusing. Under reducing conditions the dominating protein components appear as heterogeneous material of 55-70 kDa and distinct protein bands of 85, 17, 16, and 15 kDa. The heterogeneous material contains glycosylated material detected by an antiserum recognizing both human SgI and SgII. Southern blotting indicates that the common marmoset has genes for both SgI and SgII. There are several marmoset MSP genes, but the strong immunoreactivity against one 15 kDa semen component with pI 7.3 suggests preferential expression of one gene in the prostate. Expression of two other genes cannot be excluded as indicated by weak reaction to isoforms with pI 6.6 and 4.9. Unexpectedly, PSA was not detected by either immunological methods or activity measurements. This is in agreement with results from Southern blotting suggesting that the common marmoset might not have a PSA gene. Thus, in this study we have shown that semen coagulum proteins are present in marmoset seminal plasma, but the lack of PSA precludes a similar liquefaction as of human semen.