Phf7 has impacts on the body growth and bone remodeling by regulating testicular hormones in male mice

PHD finger protein 7 (Phf7) is a member of the PHF family proteins, which plays important roles in spermiogenesis. Phf7 is expressed in the adult testes and its deficiency causes male infertility. In this study, we tried to find the causal relationship between Phf7 deficiency and reduced growth retardation which were found in null knock-out (Phf7^-/-) mice. Phf7^-/- mice were born normally in the Mendelian ratio. However, the Phf7^-/- males showed decreased body weight gain, bone mineral density, and bone mineral content compared to those in wild-type (WT) mice. Histological analysis for tibia revealed increased number of osteoclast cells in Phf7^-/- mice compared with that in WT mice. When we analyzed the expressions for marker genes for the initial stage of osteoclastogenesis, such as receptor activator of nuclear factor kappa B (Rank) in tibia, there was no difference in the mRNA levels between Phf7^-/- and WT mice. However, the expression of tartrate-resistant acid phosphatase (Trap), a mature stage marker gene, was significantly higher in Phf7^-/- mice than in WT mice. In addition, the levels of testosterone and dihydrotestosterone (DHT), more potent and active form of testosterone, were significantly reduced in the testes of Phf7^-/- mice compared to those in WT mice. Furthermore, testicular mRNA levels for steroidogenesis marker genes, namely Star, Cyp11a1, Cyp17a1 and 17β-hsd, were significantly lower in Phf7^-/- mice than in WT mice. In conclusion, these results suggest that Phf7 deficiency reduces the production of male sex hormones and thereby impairs associated bone remodeling.