17β-Estradiol (E₂) is thought to be responsible for sex-specific differences in skeletal muscle mass. The
biological function of E₂ is exerted through its binding to
estrogen receptor α (ERα). The expression of
ubiquitin-specific peptidase 19 (USP19) is upregulated during
muscle atrophy and by E₂-activated ERα. Here, we investigated the involvement of USP19 in sex difference in muscle mass in young mice. Knockdown of USP19 in hindlimb muscles increased the mass and fiber size in soleus muscle in females but not males. Using Usp19 promoter reporter constructs, a functional half-
estrogen response element (hERE) was identified in intron 1 of Usp19. ERα bound to hERE in an E₂-dependent manner in C2C12 myoblasts and in soleus muscle in ovariectomized (OVX) female mice. Furthermore, under normal physiological conditions, ERα bound to hERE in soleus muscle only in females. In contrast, administration of E₂ resulted in increased Usp19
mRNA expression, decreased muscle mass, and recruitment of ERα to hERE in soleus muscle in males. Knockdown of ERα in hindlimb muscles decreased Usp19
mRNA expression and increased the mass of soleus muscle only in females. Knockdown of USP19 resulted in increased levels of
ubiquitin conjugates in soleus muscle in females. OVX increased the levels of
ubiquitin conjugates and administration of E₂ decreased OVX-induced levels of
ubiquitin conjugates. These results demonstrate that in soleus muscle in young female mice under physiological conditions, E₂ upregulates USP19 expression through ERα and consequently leads to decreases in
ubiquitin conjugates and muscle mass.