Androgen down-regulated and region-specific expression of germ cell nuclear factor in mouse epididymis

Germ cell nuclear factor (GCNF), a nuclear orphan receptor, involved in spermatogenesis, neurogenesis, differentiation, and embryo development, was highly expressed with two transcripts (7.4 and 2.3 kb) in mouse testis and with only one transcript (7.4 kb) slightly expressed in brain, liver, and kidney. The 2.3-kb transcript was restricted to round spermatids at stages VII and VIII of the spermatogenic cycle. The present report demonstrated its expression in epididymis as well, but at a very low level. Northern blot analysis showed two transcripts: a common 7.4-kb transcript and a unique 3.1-kb transcript. The expression levels of both GCNF transcripts in epididymis were down-regulated by androgen, as observed in castrated animals and aged mice. Polyclonal antisera against GCNF protein were raised. Western blot analysis showed the presence of only one band in total protein extracts from either mouse testis or epididymis. It indicated that the two mRNAs (7.4 and 3.1 kb) encode for the same protein as in testis. Fluorescent immunohistochemical staining and in situ hybridization showed that its expression was in the principal cell abundant in the corpus region. It implies that some androgen-regulated gene expressions located at the corpus principal cells might be controlled by GCNF.