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Purpose: The purpose of this study was to identify mutations that cause non-syndromic male infertility using whole exome sequencing of family cases. Methods: We recruited a consanguineous Turkish family comprising nine siblings with male triplets; two of the triplets were infertile as well as one younger infertile brother. Whole exome sequencing (WES) performed on two azoospermic brothers identified a mutation in the melanoma antigen family B4 ( MAGEB4) gene which was confirmed via Sanger sequencing and then screened for on control groups and unrelated infertile subjects. The effect of the mutation on messenger RNA (mRNA) and protein levels was tested after in vitro cell transfection. Structural features of MAGEB4 were predicted throughout the conserved MAGE domain. Results: The novel single-base substitution (c.1041A>T) in the X-linked MAGEB4 gene was identified as a no-stop mutation. The mutation is predicted to add 24 amino acids to the C-terminus of MAGEB4. Our functional studies were unable to detect any effect either on mRNA stability, intracellular localization of the protein, or the ability to homodimerize/heterodimerize with other MAGE proteins. We thus hypothesize that these additional amino acids may affect the proper protein interactions with MAGEB4 partners. Conclusion: The whole exome analysis of a consanguineous Turkish family revealed MAGEB4 as a possible new X-linked cause of inherited male infertility. This study provides the first clue to the physiological function of a MAGE protein. [ABSTRACT FROM AUTHOR]

The steroidogenic factor 1 (SF1) protein, encoded by the NR5A1 gene, plays a central role in gonadal development and steroidogenesis. Mutations in NR5A1 were first described in patients with primary adrenal insufficiency and 46,XY disorders of sexual development and later also in men with hypospadias, bilateral anorchia and micropenis and women with primary ovarian insufficiency. Recently, heterozygous missense mutations were found in 4% of infertile men with unexplained reduced sperm counts living in France, but all mutation carriers were of non-Caucasian ancestry. Therefore, we performed a comprehensive NR5A1 sequence analysis in 488 well-characterised predominantly Caucasian patients with azoo- or severe oligozoospermia. Two-hundred-thirty-seven men with normal semen parameters were sequenced as controls. In addition to several synonymous variants of unclear pathogenicity, three heterozygous missense mutations predicted to be damaging to SF1 protein function were identified. The andrological phenotype in infertile but otherwise healthy mutation carriers seems variable. In conclusion, mutations altering SF1 protein function and causing spermatogenic failure are also found in men of German origin, but the prevalence seems markedly lower than in other populations. [ABSTRACT FROM AUTHOR]