Mandal Kamal, Sarkar Rajesh K, Sen Sharma Souvik, Jain Ayushi, Majumdar Subeer S
Cellular Endocrinology Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India.
Cellular Endocrinology Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India.
Gene. 2018 Jan 30;641:18-24. doi: 10.1016/j.gene.2017.10.032. Epub 2017 Oct 12.
Globally, there is an alarming decline in sperm count. Very often hormonal supplementation fails to restore normal sperm count. Sertoli cells (Sc) present within seminiferous tubules provide appropriate niche and factors required for the differentiation of germ cells (Gc) into mature sperm (spermatogenesis). Functionally compromised Sc may be one of the reasons for failure of hormones to facilitate normal spermatogenesis. Although role of secretory proteins and signaling molecules of Sc has been studied well, role of transcription factors regulating sperm count has not been addressed appropriately. Retinoic acid receptor-related orphan receptor (ROR)-alpha is one of such transcription factors reported in testis but its role in testicular function is not yet known. In a separate study, we found abundant ROR-alpha binding sites on promoter regions of several genes upregulated in pubertal rat Sc as compared to infant Sc. Immunostaining studies also revealed presence of ROR alpha in nucleus of pubertal Sc. We generated a transgenic knockdown rat model expressing shRNA targeted to ROR-alpha under Sc specific promoter, which is transcriptionally active only at and after puberty. ROR-alpha knockdown animals were found to have abnormal association of Sc and Gc, including Gc sloughing and restricted release of sperm. The knockdown animals displayed compromised spermatogenesis leading to significant reduction in sperm count. This is the first report describing the Sc specific role of ROR-alpha in maintaining quantitatively normal sperm output. Identification of various such molecules can generate avenues to limit or reverse an alarmingly declining sperm count witnessed globally in men.
在全球范围内，精子数量出现了惊人的下降。激素补充疗法常常无法恢复正常的精子数量。生精小管内的支持细胞（Sc）为生殖细胞（Gc）分化为成熟精子（精子发生过程）提供了合适的微环境和所需因子。功能受损的支持细胞可能是激素无法促进正常精子发生的原因之一。虽然对支持细胞分泌蛋白和信号分子的作用已有充分研究，但对调节精子数量的转录因子的作用尚未得到恰当探讨。维甲酸受体相关孤儿受体（ROR）-α是睾丸中报道的此类转录因子之一，但其在睾丸功能中的作用尚不清楚。在另一项研究中，我们发现与幼年支持细胞相比，青春期大鼠支持细胞中上调的几个基因的启动子区域有大量ROR-α结合位点。免疫染色研究还显示青春期支持细胞的细胞核中存在ROR-α。我们构建了一种转基因敲低大鼠模型，该模型在支持细胞特异性启动子的作用下表达靶向ROR-α的短发夹RNA（shRNA），该启动子仅在青春期及之后具有转录活性。发现ROR-α敲低的动物支持细胞与生殖细胞的关联异常，包括生殖细胞脱落和精子释放受限。敲低动物的精子发生受损，导致精子数量显著减少。这是第一份描述ROR-α在支持细胞中对维持精子数量正常的特异性作用的报告。鉴定各种此类分子可为限制或逆转全球男性中令人担忧的精子数量下降开辟途径。
