Constitutive WNT/Beta-Catenin Signaling in Murine Sertoli Cells Disrupts Their Differentiation and Ability to Support Spermatogenesis1

Abstract

Sertoli and germ cell interactions are essential for spermatogenesis and, thus, male fertility. Sertoli cells provide a specialized microenvironment for spermatogonial stem cells to divide, allowing both self-renewal and spermatogenesis. In the present study, we used mice with a conditional activated allele of the beta-catenin gene (Ctnnb1(tm1Mmt)(/+)) in Sertoli cells expressing Cre recombinase driven by the anti-Müllerian hormone (AMH; also known as Müllerian-inhibiting substance) type II receptor promoter (Amhr2(tm3(cre)Bhr)(/+)) to show that constitutively activated beta-catenin leads to their continuous proliferation and compromised differentiation. Compared to controls, Sertoli cells in mature mutant mice continue to express high levels of both AMH and glial cell-derived neurotrophic factor (GDNF), which normally are expressed only in immature Sertoli cells. We also show evidence that LiCl treatment, which activates endogenous nuclear beta-catenin activity, regulates both AMH and GDNF expression at the transcriptional level. The epididymides were devoid of sperm in the Amhr2(tm3(cre)Bhr)(/+);Ctnnb1(tm1Mmt)(/+) mice at all ages examined. We show that the mutant mice are infertile because of defective differentiation of germ cells and increased apoptosis, both of which are characteristic of GDNF overexpression in Sertoli cells. Constitutive activation of beta-catenin in Amhr2-null mice showed the same histology, suggesting that the phenotype was the result of persistent overexpression of GDNF. These results show that dysregulated wingless-related MMTV integration site/beta-catenin signaling in Sertoli cells inhibits their postnatal differentiation, resulting in increased germ cell apoptosis and infertility.

Focal Müllerian duct retention in male mice with constitutively activated β-catenin expression in the Müllerian duct mesenchyme

“…The retained MD tissue was often accompanied by fibrosis near the adjacent tubules, which had the deleterious effect of causing obstructive azoospermia by formation of enlarged epididymal cysts (Fig. 4) of impacted sperm that resemble spermatoceles in most of the mutant mice with what little spermatogenesis was occurring in their testes before seminiferous tubule degeneration begins in Amhr2-Cre;Ctnnb1 Δ(ex3) mice when they are ∼4 wk old (18,19).…”

“…We and others have also shown that CA β-catenin causes sterility in males by inhibiting postnatal Sertoli maturation and spermatogenesis (18)(19)(20). Given the requirement for Wnt signaling in MD development (21) and the relative paucity of reports linking Wnt signaling and Wolffian duct (WD) differentiation, we examined whether dysregulated β-catenin activity in the adjacent MD mesenchyme affected normal WD development into the epididymis, vas deferens, and seminal vesicles (22,23).…”

“…Given the requirement for Wnt signaling in MD development (21) and the relative paucity of reports linking Wnt signaling and Wolffian duct (WD) differentiation, we examined whether dysregulated β-catenin activity in the adjacent MD mesenchyme affected normal WD development into the epididymis, vas deferens, and seminal vesicles (22,23). We show that CA β-catenin expression in the MD mesenchyme results in focal MD retention and adjacent WD obstruction, which leads to azoospermia and infertility secondary to seminiferous tubule degeneration and defective spermatogenesis that develops later in the adult (18,19).…”

Transcriptome profiling of the developing postnatal mouse testis using next-generation sequencing

“…It regulates the self-renewal and differentiation of spermatogonial stem cells; however, the balance of self-renewal and differentiation of spermatogonial stem cells is influenced not only by intracellular signals, but also by the microenvironment, termed the spermatogonial stem cell niche, which is formed by surrounding Sertoli cells [76]. By regulating the differentiation and maturation of Sertoli cells, the Wnt signaling pathway has an ability to support spermatogenesis [77]. We found that the transcriptional activity of the Wnt signaling pathway decreases in PN2.…”

Aberrant Wnt/β-Catenin Signaling Pathway in Testis of Azoospermic Men​

“…22 Overexpression of β-catenin leads to uncontrolled proliferation, inhibition of differentiation in Sertoli cells and their function to support germ cells in mice. 23 As a result, relationship of Wnt/β-catenin signaling dysfunction in sertoli, germ cell, and infertility has been confirmed. Leydig cells have not been studied in this regard.…”