CRISPR/Cas9-mediated Dax1 Knockout in the Monkey Recapitulates Human AHC-HH

Mutations in the DAX1 locus cause X-linked adrenal hypoplasia congenita (AHC) and hypogonadotropic hypogonadism (HH), which manifest with primary adrenal insufficiency and incomplete or absent sexual maturation, respectively. The associated defects in spermatogenesis can range from spermatogenic arrest to Sertoli cell only syndrome. Conclusions from Dax1 knockout mouse models provide only limited insight into AHC/HH disease mechanisms, because mouse models exhibit more extensive abnormalities in testicular development, including disorganized and incompletely formed testis cords with decreased number of peritubular myoid cells and male-to-female sex reversal. We previously reported successful clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9)-mediated genome targeting in cynomolgus monkeys. Here, we describe a male fetal monkey in which targeted genome editing using CRISPR/Cas9 produced Dax1-null mutations in most somatic tissues and in the gonads. This DAX1-deficient monkey displayed defects in adrenal gland development and abnormal testis architecture with small cords, expanded blood vessels and extensive fibrosis. Sertoli cell formation was not affected. This phenotype strongly resembles findings in human patients with AHC-HH caused by mutations in DAX1. We further detected upregulation of Wnt/β-catenin-VEGF signaling in the fetal Dax1-deficient testis, suggesting abnormal activation of signaling pathways in the absence of DAX1 as one mechanism of AHC-HH. Our study reveals novel insight into the role of DAX1 in HH and provides proof-of-principle for the generation of monkey models of human disease via CRISPR/Cas9-mediated gene targeting.