Expression and regulation of type II integral membrane protein family members in mouse male reproductive tissues.

Type II Integral membrane protein (Itm2) family consists of three members, Itm2a, Itm2b and Itm2c. ITM2B has been shown to be closely related to human male reproduction. The expression and regulation of Itm2 family members in male reproductive tissues are still unknown. The aim of the present study was to examine the expression pattern and regulation of Itm2 family members in male mouse reproductive tissues during sexual maturation, castration, and busulfan treatment by in situ hybridization. During sexual maturation, a low level of Itm2a was detected in testicular interstitium on days 30-70. Itm2b expression was basally detected in the epithelium of seminiferous tubules on days 1, 5, and 10, and then the signal was transited into Leydig cells and gradually increased up to day 70. Itm2c was detected at a basal to low level in the testis during sexual maturation. Both Itm2a and Itm2c were not detected in the epididymis and vas deferens during sexual maturation. In contrast, Itm2b expression was detected in the epithelium of caput, corpus, cauda epididymis, and vas deferens from neonate to adult mice. In the caput, Itm2b expression reached the highest level on day 15 and maintained this level up to day 70. However, in corpus and cauda epididymis, the signals gradually reached a high level from days 15 to 70. In vas deferens, Itm2b gradually increased to a high level from days 25 to 70. In the castrated mice, Itm2b expression was upregulated in epididymis and vas deferens by testosterone treatments. When busulfan was used to specifically destroy the germ cells in the testis, there were no observable effects on Itm2b expression in the male reproductive organs. Our results suggested that Itm2b mRNA was differentially expressed in mouse male reproductive tissues, during sexual maturation and up-regulated by testosterone.