Identification of four novel variant in the AMHR2 gene in six unrelated Turkish families

Two novel AMHR2 gene variants in monozygotic twins with persistent Müllerian duct syndrome: A case report and functional study

Background

Persistent Müllerian duct syndrome (PMDS) is an autosomal recessive congenital abnormality in which Müllerian derivatives, uterus, cervix, upper two‐thirds of the vagina, and fallopian tubes persist in otherwise normally virilized males. Mutations in anti‐Müllerian hormone (AMH) and AMH receptor type II (AMHR2) genes have been identified as causative. However, functional experimental analysis of AMHR2 or AMH variants that cause PMDS is still lacking.

Materials and Methods

A Chinese Han family affected by PMDS was identified. To assess the history and clinical manifestations of PMDS, physical, operational, ultrasonographical, pathological, and other examinations were performed on family members. The variant screening was conducted using trio whole‐exome sequencing (trio WES) and Sanger sequencing. Complementation‐based NanoLuciferase Binary Technology (NanoBiT) was used to examine the interaction between AMH and AMHR2 variants in vivo. The effect of the two variants on the transcriptional activity of the TGFβ/BMP pathway was evaluated using a luciferase assay.

Results

Classic phenotypic manifestations of PMDS in a pair of identical twins were described and confirmed by genetic sequence analysis. Molecular studies revealed two novel variants c.118G > C [p.(Gly40Arg)], c.1222G > C [p.(Ala408Pro)] in the AMHR2 gene. The AMHR2 p.Gly40Arg variant reduces its ability to bind to AMH, while the p.Ala408Pro variant alters the kinase domain structure. Both variants significantly reduce TGFβ/BMP signaling.

Conclusion

Two missense AMHR2 variants associated with PMDS were identified. These findings provide novel insights toward better clinical evaluation and further understanding of the molecular basis of PMDS.

Identification of AMH and AMHR2 Variants Led to the Diagnosis of Persistent Müllerian Duct Syndrome in Three Cases

Persistent Müllerian duct syndrome (PMDS) is a rare autosomal recessive disorder of sexual development in males, defined by the presence of Müllerian remnants with otherwise normal sexual differentiation. Mutations in anti-Müllerian hormone (AMH) and AMH receptor type 2 (AMHR2) genes are the main causes of PMDS. In this study, we performed molecular genetic analysis of 11 unrelated cryptorchidism patients using whole-exome sequencing and classified the variants. Three of the 11 patients had biallelic mutations in AMH or AMHR2. Case 1 carried a homozygous 4-bp deletion; c.321_324del:p.Q109Lfs*29 in exon 1 of AMH (NM_000479 transcript), which is a frameshift mutation, leading to the loss of function of AMH. Case 2 carried compound heterozygous mutations; c.494_502del (p.I165_A168delinsT) in exon 4 and g.6147C>A of AMHR2 (NM_001164690 transcript). Case 3 carried compound heterozygous mutations; c.G1168A (p.E390K) in exon 9 and c.A1315G (p.M439V) in exon 10 of AMHR2 (NM_001164690 transcript). All three patients were admitted due to azoospermia- and oligospermia-caused infertility. They were furtherly diagnosed with PMDS, as pelvic magnetic resonance imaging revealed the presence of Müllerian remnants. Our study suggests that PMDS and genetic analysis should be considered during the differential diagnosis of cryptorchidism.