This finding explains why ARMCX2 is upregulated in patients with FXS (Rosales-Reynoso et al., 2010), which is characterized by methylation of the FMR1 promoter region (Bagni and Oostra, 2013), and how ARMCX2 participates in the development of a variety of tissues during embryogenesis, particularly testicular tissue differentiation (Smith et al., 2005). Here, ARMCX2 is linked to fragile X syndrome.