Sertoli cell specific decline in NOR‐1 leads to germ cell apoptosis and reduced fertility

Abstract

The somatic component of seminiferous epithelium, the Sertoli cells (Sc) respond to Follicle stimulating hormone (FSH), and Testosterone (T) to produce factors which are necessary for germ cell (Gc) survival and differentiation. Infant Sc do not support spermatogenesis in spite of sufficient hormonal milieu, a situation similar to that found in male idiopathic infertility. Sc maturation during pubertal period involves expression of some genes which may be important for initiation of spermatogenesis. Analysis of differentially expressed genes, one by one, in infant and pubertal Sc might provide useful information about the regulation of spermatogenesis. DNA microarray based analysis of mRNA from 5-days (infant) and 12-days (pubertal) old rat Sc revealed increased expression of Nor-1 by pubertal Sc. NOR-1 is an orphan nuclear receptor involved in maintaining cellular homeostasis and disease. We generated transgenic mice using shRNA cloned under Pem (Rhox5) promoter which is activated at puberty in Sc. Such transgenic mice had reduced Nor-1 expression and increased Tgfβ1, Tgfβ3, and Smad3 expression. Moreover, an increase in β-catenin expression was observed in NOR-1 knockdown testes. High β-catenin in such transgenic mice was found to be associated with disruption of Sc maturation characterized by elevated expression of Anti Mullerian hormone, Cytokeratin 18, and Sox9. This disruption of Sc maturation resulted in Gc apoptosis. Such NOR-1 knockdown mice showed reduced sperm count and litter size. We report for the first time that NOR-1 plays a crucial role in regulating sperm count and male fertility.

Homeobox transcription factor Meis1 is crucial to Sertoli cell mediated regulation of male fertility

“…We have shown in the past that besides hormones, a number of Sc gene products play an important role in maintenance of Sc function, crucial for spermatogenesis 16,25,27 . A number of transcription factors such as SOX9, WT1, and GATA4 are known to regulate Sc development and maturation 28 .…”

“…MEIS1 expression in the transgenic mice was found to be significantly down‐regulated as compared to age‐matched control animals, indicating efficient knockdown of MEIS1 by shRNA in the transgenic mice. Wild‐type mice were used as a control in our experiments as we have previously demonstrated that LacZ knockdown transgenic mice are phenotypically similar to wild‐type mice 25 …”

“…Terminal deoxynucleotidyl transferase (TdT) dUTP Nick‐End Labeling (TUNEL) assay was used for detecting apoptotic cells in Meis1 KD and wild‐type mice testicular sections. TUNEL assay was performed using DeadEnd™ Colorimetric TUNEL System (Promega) as described previously 25 . The total number of apoptotic germ cells was recorded from ten random fields (under 20× magnification) of the testicular sections of wild‐type and transgenic mice.…”

The function of nuclear hormone receptor 4A signaling in the human reproductive system: A review

“…Correspondingly, epididymal sperm count also indicated that the number of spermatozoa of NR4A3 knockdown mice was significantly declined. They suggest that perturbations in NR4A3 functioning might lead to a reduction in the number of sperm and this may be one of several as yet unidentified causes of male idiopathic infertility 88 . Together, these data highlight the importance of NR4A family receptors as regulators of spermatogenesis and male fertility.…”

Declining levels of miR-382-3p at puberty trigger the onset of spermatogenesis

“…The fertility assessment was done by measuring parameters like gonadosomatic index, sperm count, and litter size in the transgenic and age-matched wild-type mice. 53,[80][81][82] The body weight and testis weight for each mouse (WT or transgenic) was noted, and the gonadosomatic index (body weight/testis weight  100) was calculated. The testis size was also observed for any visible morphological changes.…”