Abstract: 122

EXPRESSION OF GENES ENCODING THE MEDIATORS OF ACTIVIN SIGNALING, SMADS, IN MALE REPRODUCTIVE TRACT.

Ai Zhen Wu¹ , Zong-Ming Feng¹ , Ching-Ling C. Chen^{1 2}
Population Council, New York, NY ¹
Rockefeller University, New York, NY ²

Activins are known to modulate diverse functions within and outside of the reproductive system. The actions of activins on male reproductive tract were further confirmed by our demonstration of the expression of both type II and IIB activin receptors in these tissues. Recent studies concluded that the activin signaling from its receptor at the cell membrane to the nucleus is mediated through SMAD protein family, Smad2, Smad3 and Smad4. To delineate the mechanisms of activin actions in male reproductive tract, we have studied the expression of the three Smad genes in these tissues. All three Smad mRNAs were identified in the testis and prostate of rat at the age of 7-80 days. Two species, 2.6 and 2.0 kb, of Smad2 mRNA were observed in rat testis, and one additional 6.5-kb mRNA was found in rat prostate. One major species of 5.4-kb Smad3 mRNA and 3.6-kb Smad4 mRNA were identified. In testis, a testis-specific 4.6-kb Smad3 mRNA was also found. Except the 2.0-kb Smad2 mRNA, all three Smad mRNAs were expressed in maximal levels in immature testis of 7- to 21-days. These findings are in good agreement with our previous observations of the expression of the 6.0-kb type II activin receptor in the testis, suggesting that activin receptor and its mediators, Smads, are coordinately expressed during testicular development and are probably expressed in the same testicular cell types, such as, spermatogonia and Sertoli cells. In addition to the testis and prostate, the three Smad mRNAs were also identified in other male reproductive tract organs, epididymis, seminal vesicles and vas deferens with maximal expressions in young animals. In conclusion, activin receptors and the mediators of activin signaling, Smads, are coexpressed in the male reproductive tract tissues.

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