R31C GNRH1 mutation and congenital hypogonadotropic hypogonadism.

Luigi Maione, Frederique Albarel, Philippe Bouchard, Megan Gallant, Colleen A Flanagan, Regis Bobe, Joelle Cohen-Tannoudji, Rosario Pivonello, Annamaria Colao, Thierry Brue, Robert P Millar, Marc Lombes, Jacques Young, Anne Guiochon-Mantel, Jerome Bouligand

Index: PLoS ONE 8(7) , e69616, (2013)

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Abstract

Normosmic congenital hypogonadotropic hypogonadism (nCHH) is a rare reproductive disease leading to lack of puberty and infertility. Loss-of-function mutations of GNRH1 gene are a very rare cause of autosomal recessive nCHH. R31C GNRH1 is the only missense mutation that affects the conserved GnRH decapeptide sequence. This mutation was identified in a CpG islet in nine nCHH subjects from four unrelated families, giving evidence for a putative "hot spot". Interestingly, all the nCHH patients carry this mutation in heterozygosis that strikingly contrasts with the recessive inheritance associated with frame shift and non-sense mutations. Therefore, after exclusion of a second genetic event, a comprehensive functional characterization of the mutant R31C GnRH was undertaken. Using different cellular models, we clearly demonstrate a dramatic reduction of the mutant decapeptide capacity to bind GnRH-receptor, to activate MAPK pathway and to trigger inositol phosphate accumulation and intracellular calcium mobilization. In addition it is less able than wild type to induce lh-beta transcription and LH secretion in gonadotrope cells. Finally, the absence of a negative dominance in vitro offers a unique opportunity to discuss the complex in vivo patho-physiology of this form of nCHH.