Membrane-Localized Estrogen Receptor 1 Is Required for Normal Male Reproductive Development and Function in Mice

Estrogen receptor 1 (ESR1) mediates major reproductive functions of 17β-estradiol (E2). Male Esr1 knockout (Esr1KO) mice are infertile due to efferent ductule and epididymal abnormalities. The majority of ESR1 is nuclear/cytoplasmic; however, a small fraction is palmitoylated at cysteine 451 in mice and localized to cell membranes, in which it mediates rapid E2 actions. This study used an Esr1 knock-in mouse containing an altered palmitoylation site (C451A) in ESR1 that prevented cell membrane localization, although nuclear ESR1 was expressed. These nuclear-only estrogen receptor 1 (NOER) mice were used to determine the roles of membrane ESR1 in males. Epididymal sperm motility was reduced 85% in 8-month-old NOER mice compared with wild-type controls. The NOER mice had decreased epididymal sperm viability and greater than 95% of sperm had abnormalities, including coiled midpieces and tails, absent heads, and folded tails; this was comparable to 4-month Esr1KO males. At 8 months, daily sperm production in NOER males was reduced 62% compared with controls. The NOER mice had histological changes in the rete testes, efferent ductules, and seminiferous tubules that were comparable with those previously observed in Esr1KO males. Serum T was increased in NOER males, but FSH, LH, and E2 were unchanged. Critically, NOER males were initially subfertile, becoming infertile with advancing age. These findings identify a previously unknown role for membrane ESR1 in the development of normal sperm and providing an adequate environment for spermatogenesis.

Estrogen-Dependent and -Independent Estrogen Receptor-α Signaling Separately Regulate Male Fertility

Estrogen receptor-α (ERα) plays a critical role in male reproductive tract development and fertility. To determine whether estrogen-dependent and -independent ERα mechanisms are involved in male fertility, we examined male estrogen nonresponsive ERα knock-in mice. These animals have a point mutation (G525L) in the ligand-binding domain of ERα that significantly reduces interaction with, and response to, endogenous estrogens but does not affect growth factor activation of ligand-independent ERα pathways. Surprisingly, we found that ligand-independent ERα signaling is essential for concentrating epididymal sperm via regulation of efferent ductule fluid reabsorption. In contrast, estrogen-dependent ERα signaling is required for germ cell viability, most likely through support of Sertoli cell function. By treating estrogen nonresponsive ERα knock-in (ENERKI) mice with the ERα selective synthetic agonist propyl pyrazole triol, which is able to bind and activate G525L ERα in vivo, we discovered male fertility required neonatal estrogen-mediated ERα signaling. Thus, our work indicates both estrogen-dependent and -independent pathways play separable roles in male murine reproductive tract development and that the role of ERα in human infertility should be examined more closely.

Testicular Efferent Ductule Cyst of a Dog

A 9-year-old male Shetland Sheepdog had a small mass in the left testis. Grossly, the round to oval cyst was present at the upper pole of the testicular parenchyma near the head of the epididymis. Histologically, the cyst was lined by a single layer of nonciliated and ciliated epithelial cells. Immunohistochemically, the epithelial cells of the cyst showed expression of the low- and high-molecular-weight cytokeratins, vimentin, and desmin similar to that of normal efferent ductules in the dog. The testicular cystic dysplasia was thought to originate from the efferent ductules.