Differential expression pattern of retinoid X receptors in adult murine testicular cells implies varying roles for these receptors in spermatogenesis

Retinoids have previously been shown to be crucial for normal spermatogenesis. The role of retinoic acid receptors has been studied, but relatively little is known about the function of retinoid X receptors (RXRs). To gain more insight in the function of RXRs during spermatogenesis, the cellular localization of RXRs in the mouse testis was examined using immunohistochemistry and RNase protection assays. In both normal and vitamin A-deficient (VAD) testes, a strong immune response to an RXRα antibody occurred in Leydig cells, peritubular myoid cells, and A spermatogonia. Weaker signals were found in spermatocytes and spermatids. In normal testes, an RXRβ antibody gave a reaction in Leydig cells, and, to a lesser extent, in Sertoli cells, A spermatogonia, pachytene spermatocytes, and spermatids. In Leydig cells, a cytoplasmatic signal was found in addition to the nuclear signal. In the VAD testis, only Leydig cells and A spermatogonia were positive, which indicates that RXRβ expression may be dependent on the retinoid status. Previous studies have shown RXRγ mRNA expression in the mouse testis at a low level. Nevertheless, an RXRγ antibody caused a strong immune response in interstitial cells and in A spermatogonia, and a weak signal in pachytene spermatocytes. These immunohistochemical data were supported by the results of RNase protection assays on mRNA of testicular cell isolations. In conclusion, the different RXRs in the mouse testis have distinct expression patterns, suggesting that they may have different functions.

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