Autoregulation of testicular luteinizing hormone receptors in hypogonadal (hpg/hpg) mice

Loss of microRNA-7a2 induces hypogonadotropic hypogonadism and infertility

MicroRNAs (miRNAs) are negative modulators of gene expression that fine-tune numerous biological processes. miRNA loss-of-function rarely results in highly penetrant phenotypes, but rather, influences cellular responses to physiologic and pathophysiologic stresses. Here, we have reported that a single member of the evolutionarily conserved miR-7 family, miR-7a2, is essential for normal pituitary development and hypothalamic-pituitary-gonadal (HPG) function in adulthood. Genetic deletion of mir-7a2 causes infertility, with low levels of gonadotropic and sex steroid hormones, small testes or ovaries, impaired spermatogenesis, and lack of ovulation in male and female mice, respectively. We found that miR-7a2 is highly expressed in the pituitary, where it suppresses golgi glycoprotein 1 (GLG1) expression and downstream bone morphogenetic protein 4 (BMP4) signaling and also reduces expression of the prostaglandin F2a receptor negative regulator (PTGFRN), an inhibitor of prostaglandin signaling and follicle-stimulating hormone (FSH) and luteinizing hormone (LH) secretion. Our results reveal that miR-7a2 critically regulates sexual maturation and reproductive function by interconnecting miR-7 genomic circuits that regulate FSH and LH synthesis and secretion through their effects on pituitary prostaglandin and BMP4 signaling.

Effects of estrogen and ectopic pituitary transplants on the responsiveness of pituitary prolactin release to luteinizing hormone-releasing hormone and dopamine

Abstract The responsiveness of prolactin release to regulatory inputs depends on the functional state of the lactotrophs. In the present study, we have examined the effects of luteinizing hormone-releasing hormone (LHRH; 10(-7) or 10(-6) M) on the release of prolactin in vitro from hyperplastic pituitaries of estrogen-treated male Fischer rats, ectopic pituitary transplants and in situ pituitaries of grafted and control rats. The effects of dopamine (10(-8) or 10(-7) M) in this system were also examined. The extent of inhibition of prolactin release by dopamine was not related to the amounts of prolactin secreted under basal conditions or to plasma prolactin levels. LHRH significantly suppressed prolactin secretion in all groups but its effect was most pronounced in the ectopic pituitary transplants and in the hyperplastic pituitaries of animals after chronic exposure to estrogen followed by a period of recovery. Thus, the effects of LHRH on prolactin release appear to be related to the secretory activity and/or to the absolute or relative number of the lactotrophs.