Two Novel AMHR2 Gene Variants in Monozygotic Twins with Persistent Müllerian Duct Syndrome

Background: Persistent müllerian duct syndrome (PMDS) is an autosomal recessive congenital abnormality for which müllerian derivatives, uterus, cervix, upper 2/3 vagina and fallopian tubes, persist in an otherwise normally virilized males. Mutations in the AMH gene and AMHR2 gene have been identified as causative. However, there has been no functional experimental analysis of AMHR2 or AMH variants that caused PMDS. We ascertained a Chinese PMDS pedigree. To elucidate the pathogenic mechanisms of variant, we used complementation-based NanoLuciferase Binary Technology (NanoBiT) to examine AMH and AMHR2 variants interaction in vivo. Using an ID-1 luciferase assay, we probed the effect of the two variants on the transcriptional activity of the TGFβ/BMP pathway. Results: Molecular studies revealed two novel variants [c.118G>C/p. Gly40Arg, c.1222G>C/p. Ala408Pro] in the AMHR2 gene of our monozygotic boys. The AMHR2 p. Ala408Pro variants affect a functional domain, result in impaired substrate recognition and affinity. For p.Gly40Arg variant, the arginine residue will disfigure the local backbone and alter function. The AMHR2 p.Gly40Arg variant reduces its ability to bind to AMH, while the p.Ala408Pro variant alters the kinase domain structure. Conclusion: Both variants significantly reduce TGFβ/BMP signaling. This study provides new methods and concepts as to the study of the molecular pathogenic mechanism of PMDS.