Seminiferous tubule degeneration and infertility in mice with sustained activation of WNT/CTNNB1 signaling in sertoli cells

To elucidate the role(s) of WNT/CTNNB1 signaling in the testis, transgenic Ctnnb1 tm1Mmt/+;Amhr2 tm3(cre)Bhr/+ mice were generated to obtain sustained activation of the WNT/CTNNB1 pathway in Sertoli cells. Male Ctnnb1 tm1Mmt/+;Amhr2 tm3(cre)Bhr/+ mice were sterile because of testicular atrophy starting at 5 wk of age, associated with degeneration of seminiferous tubules and the progressive loss of germ cells. Sustained WNT/CTNNB1 pathway activation was obtained in Ctnnb1 tm1Mmt/+;Amhr2 tm3(cre)Bhr/+ Sertoli cells. Sertoli cells often exhibited morphological characteristics suggestive of incomplete differentiation that appeared in a manner coincident with germ cell loss, accompanied by an increase in the expression of the immature Sertoli cell marker AMH. Microarray analyses performed on cultured Sertoli cells showed that CTNNB1 induces the expression of genes associated with the female sex determination pathway as well as cell-cycle associated genes . Together, these data suggest that the WNT/CTNNB1 pathway regulates Sertoli cell functions critical to their capacity to support spermatogenesis and to proliferate in the postnatal testis. Sertoli cells were obtained from 3wks-old Ctnnb1(tm1Mmt/tm1Mmt) mice. Cells were infected with adenoviruses to express eGFP or Cre in serum-free medium, and subsequently harvested for RNA extraction. Preliminary experiments demonstrated that an infection efficiency of nearly 100% could be obtained at an MOI of 50 (as determined by analysis of fluorescent signal in Ad-eGFP-infected cells) and that the Ad-Cre virus produced complete recombination of the floxed Ctnnb1 allele after 12 hours. Microaaray analyses were done using triplicate RNA samples from each adenoviral treatment using MouseRef-6 v.2.0 expression BeadChips technology (Illumina, San Diego, CA).