The cellular expression of GABAA receptor a1 subunit during spermatogenesis in the mouse testis

Abstract

GABAA receptors are pentamers in structure and are mainly composed of α, ß and γ subunits. These receptors are known to function as chloride channels. We observed α5, ß1 and γ3 subunit immunoreactivity in the mouse testes, specifically in the cytoplasm surrounding the nucleus in the spermatocytes and spermatids. In the current study, α1 subunit immunoreactivity was located in the nucleus of spermatogonia, spermatocytes and round spermatids. Immunoelectron microscopy revealed that the α1 subunit was localized within the nucleus of pachytene and diplotene spermatocytes in the area of condensed chromatin rather than extended chromatin. Protein sequence analysis revealed that the α1 subunit included DM DNA binding domains that were related to transcription factors involved in testicular differentiation in adult mice. These findings suggest that the α1 subunit may undertake a gene transcription function during the maturation of germ cells. α1 immunoreactivity was also detected within the mitochondria of spermatocytes and in the acrosome of round and elongated spermatids. Although the precise physiological role of the GABAA receptor α1 subunit in mitochondria remains unknown, we hypothesize that its function in the acrosome may be related to the acrosome reaction during fertilization or during spermatogenesis.