[Impact of overexpressed FOXJ2 on mouse spermatogenesis and its action mechanism]

Objective: To analyze the phenotype of the male reproductive system in the germline-specific conditional Foxj2 knock-in mouse model (Stra8-cre; Foxj2tg/+), identify a target gene of the transcription factor FOXJ2, and investigate the effect of the overexpression of Foxj2 on mouse spermatogenesis and its action mechanism.

Methods: Based on the Cre-loxP recombination system, we generated a germline-specific conditional Foxj2 knock-in mouse model (Stra8-cre; Foxj2tg/+). We determined male fertility by counting the number of pups per litter and the fertilization rate after intracytoplasmic sperm injection (ICSI), observed the morphology of the testes and epididymides by HE staining, examined the sperm quality by computer assisted sperm analysis (CASA), detected the expression and localization of Cx43 in the testis by RT-qPCR, Western blot and immunohistochemistry, and verified the binding site of FOXJ2 to the Cx43 promoter using ChIP-PCR and dual luciferase reporter assay.

Results: The number of pups per litter and fertilization rate after ICSI were lower in the Stra8-cre; Foxj2tg/+ male mice than in the controls, and so were the size and weight of the testis. HE staining exhibited obvious exfoliation of germ cells and dramatically decreased spermatocytes and spermatids in the seminiferous tubules of the Stra8-cre; Foxj2tg/+ mice. Moreover, sperm concentration in the cauda epididymides was reduced, and the transcription and expression levels of Cx43 in the testis were increased. ChIP-PCR and dual luciferase reporter assay showed direct binding of FOXJ2 to the Cx43 promoter in the testis.

Conclusions: Overexpressed FOXJ2 may lead to spermatogenic failure and subfertility in Stra8-cre; Foxj2tg/+ male mice by upregulating the expression of Cx43.