Genetic analysis of IRF6, a gene involved in craniofacial midline formation, in relation to pituitary and facial morphology of patients with idiopathic growth hormone deficiency.

INTRODUCTION

Growth hormone is secreted by the pituitary gland, which forms part of the craniofacial midline. IRF6 encodes a transcription factor involved in the development of the craniofacial midline and mutations in IRF6 are known to disturb craniofacial development. Craniofacial and pituitary development are closely related. After whole exome sequencing revealed a new mutation in IRF6 in a family with Idiopathic Growth Hormone Deficiency (IGHD), we screened the remainder of our IGHD cohort for mutations in this gene and related their genotypes to pituitary and craniofacial morphology.

MATERIALS AND

METHODS

We sequenced all coding exons and exon-intron boundaries of IRF6 in 81 patients with IGHD. We performed a multiplex ligation-dependent probe amplification (MLPA) in order to exclude copy number variations in IRF6. We analyzed facial measurements taken from standardized digital pictures of 48 patients.

RESULTS

We found two new variants and eleven polymorphisms. Apart from the new mutation found in the index family (p.Arg233Cys), we found one other new heterozygous missense mutation in IRF6 (Pro456Ser). p.Arg233Cys was reported as extremely rare in exome databases (1 allele out of 120.852 alleles sequenced), strictly conserved among species and was predicted deleterious by all variant predictor programs. Pro456Ser was predicted to be benign. MLPA did not reveal any exon deletions or duplications in any of the patients.

CONCLUSION

This is the first report of IRF6 analysis in an IGHD cohort. We found one new mutation which, based on in silico analysis, could be of functional relevance. However, we did not find any mutations in the other patients. Therefore, we conclude that IRF6 defects are rare in IGHD patients and further research should focus on new candidate genes.