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Anne-Lise Lecoq, Jérôme Bouligand, Mirella Hage, Laure Cazabat, Sylvie Salenave, Agnès Linglart, Jacques Young, Anne Guiochon-Mantel, Philippe Chanson and Peter Kamenický

Context

Recently, germline and somatic GPR101 p.(E308D) mutation was found in patients with isolated acromegaly. It is not known whether GPR101 point mutations are associated with other histological types of pituitary adenoma.

Objective

We sought germline GPR101 mutations in patients with sporadic pituitary adenomas, and compared the phenotypes of GPR101 mutation carriers and AIP mutation carriers.

Design

An observational cohort study performed between 2007 and 2014 in a single referral center.

Participants

This prospective study involved 766 unselected patients (413 women) with sporadic pituitary adenomas of all histotypes.

Methods

Entire GPR101 and AIP coding sequence were screened for germline mutations.

Results

Twelve patients (1.6%) were found to carry the GPR101 p.(E308D) mutation or rare GPR101 variants. The minor allele frequency of the GPR101 mutation and variants was higher in patients with pituitary adenomas than in unaffected individuals included in the Exome Aggregation Consortium database. Three of the six patients with the GPR101 p.(E308D) mutation had adult-onset acromegaly, two had adrenocorticotropin-secreting adenomas, and one had a nonfunctioning macroadenoma. Six patients carried rare GPR101 variants. Germline AIP mutations or rare AIP variants were identified in 32 patients (4.2%). AIP mutation carriers were younger at diagnosis than GPR101 mutation carriers and non carriers. None of the patients harbored mutations in both the GPR101 and AIP genes.

Conclusion

Germline GPR101 mutations are very rare in patients with sporadic pituitary adenomas of various histotypes. No digenism with AIP was identified. Further studies are required to establish whether and how genetic variation in GPR101 gene contributes to pituitary tumorigenesis.

Open access

Roberto Salvatori, Serban Radian, Yoan Diekmann, Donato Iacovazzo, Alessia David, Plamena Gabrovska, Giorgia Grassi, Anna-Marie Bussell, Karen Stals, Astrid Weber, Richard Quinton, Elizabeth C Crowne, Valentina Corazzini, Lou Metherell, Tara Kearney, Daniel Du Plessis, Ajay Kumar Sinha, Atik Baborie, Anne-Lise Lecoq, Philippe Chanson, Olaf Ansorge, Sian Ellard, Peter J Trainer, David Balding, Mark G Thomas and Márta Korbonits

Objective

Mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene are associated with pituitary adenoma, acromegaly and gigantism. Identical alleles in unrelated pedigrees could be inherited from a common ancestor or result from recurrent mutation events.

Design and methods

Observational, inferential and experimental study, including: AIP mutation testing; reconstruction of 14 AIP-region (8.3 Mbp) haplotypes; coalescent-based approximate Bayesian estimation of the time to most recent common ancestor (tMRCA) of the derived allele; forward population simulations to estimate current number of allele carriers; proposal of mutation mechanism; protein structure predictions; co-immunoprecipitation and cycloheximide chase experiments.

Results

Nine European-origin, unrelated c.805_825dup-positive pedigrees (four familial, five sporadic from the UK, USA and France) included 16 affected (nine gigantism/four acromegaly/two non-functioning pituitary adenoma patients and one prospectively diagnosed acromegaly patient) and nine unaffected carriers. All pedigrees shared a 2.79 Mbp haploblock around AIP with additional haploblocks privately shared between subsets of the pedigrees, indicating the existence of an evolutionarily recent common ancestor, the ‘English founder’, with an estimated median tMRCA of 47 generations (corresponding to 1175 years) with a confidence interval (9–113 generations, equivalent to 225–2825 years). The mutation occurred in a small tandem repeat region predisposed to slipped strand mispairing. The resulting seven amino-acid duplication disrupts interaction with HSP90 and leads to a marked reduction in protein stability.

Conclusions

The c.805_825dup allele, originating from a common ancestor, associates with a severe clinical phenotype and a high frequency of gigantism. The mutation is likely to be the result of slipped strand mispairing and affects protein–protein interactions and AIP protein stability.