Extra-germ cell expression of mouse nuclear receptor subfamily 6, group A, member 1 (NR6A1)

Nuclear receptor subfamily 6, group A, member 1 (NR6A1) is an orphan member of the nuclear receptor superfamily and is required for normal mouse embryonic development. In adult mice, NR6A1 is predominantly expressed in spermatogenic cells and growing oocytes of the gonads and has a role in female reproduction by modulating the transcription of the oocyte-specific genes bone morphogenetic protein 15 (Bmp15) and growth differentiation factor 9 (Gdf9). In our goal to further understand the functional role of NR6A1 during postnatal development, we generated a Nr6a1:beta-galactosidase (LacZ) knockin reporter (Nr6a1(LacZ/+)) mouse line in which the Nr6a1:LacZ fusion gene was expressed and then characterized Nr6a1 expression in these reporter mice by performing LacZ staining. Our RT-PCR analyses showed that Nr6a1 was expressed in a variety of somatic tissues (e.g., oviduct and lung) other than gonads of normal adult mice. In adult Nr6a1(LacZ/+) mice, robust LacZ staining was observed in the gametes of gonads. Strong positive LacZ staining was also observed in the sperm of the epididymis, epithelial cells of the oviduct, and bronchioles within the lung. In adult Nr6a1(LacZ/+) mice, positive LacZ staining was observed in other somatic tissues, including hippocampus, cerebral cortex, cerebellum, and thalamus of brain; pars intermedia and pars anterior of pituitary; parathyroid; and islet of pancreas. NR6A1 expression in sperm within the epididymis, epithelial cells in the oviduct, and bronchioles of the lung was further confirmed by immunohistochemical studies. Nr6a1 is expressed not only in the germ cells of mouse gonads but also in a variety of somatic tissues, including epididymis, oviduct, brain, and pituitary. The extra-germ cell expression of NR6A1 makes it a less attractive contraceptive.