Influence of GH Receptor Gene Variants within Coding and Intronic Regions in Children with Idiopathic Short Stature (ISS) on Height and Components of the GH/IGF-I/IGFBP System

MARIA GABRIELA BALLERINI; PAULA SCAGLIA; IGNACIO BERGADA; ALICIA MARTÍNEZ; MERCEDES ALTUBE; ANA KESELMAN; DÉBORA BRASLAVSKY; MARÍA GABRIELA ROPELATO; HÉCTOR JASPER; HORACIO DOMENÉ

San Diego

Congreso; 97th. Annual Meeting of the Endocrine Society; 2015

The Endocrine Society

Background: More than 90 GHR gene mutations have been described in complete GH insensitivity (GHI), nevertheless, only few heterozygous GHR genetic variants have been associated to GHI. Little information regarding the impact of common polymorphisms within coding (Ex) and intronic (In) GHRregions on height and components of the GH/IGF-I/IGFBPs system is available. Aim: To test if GHR gene polymorphisms are associated to height and components of the GH/IGF-I/IGFBPs system in ISS children. Methods: GHR gene (Ex/In flanking regions) was PCR-amplified and sequenced in 75 unrelated ISS children. The GHR pseudoexon (6Psi) mutation was investigated by RFLP. GHR gene variants were classified as rare (minor allele frequency (MAF) ≤ 1%), less frequent (1-10%) and common (≥ 10%). To test the genotype influence of SNPs with MAF > 10% (HapMap-Project) on height and GH/IGF-I/IGFBPs system, ISS children were grouped as homozygous for the major allele and carriers of one or two copies of the minor allele. The proportion of variants (less than 3 versus 4 or more) was evaluated according to the median value of: height (-2.86 SDS), GHBP (-0.9 SDS; in house functional assay), maximal stimulated-GH (14.9 ng/L), IGF-I (-1.4 SDS), IGFBP-3 (-1.0 SDS, ICMA) and ALS (-1.3 SDS; RIA). Hardy-Weinberg equilibrium, Fisher´s exact test and Mann-Whitney analysis were used. Results: Six common and 5 less frequent variants were identified: Ex3 deletion (MAF: 26%), rs6179 (Ex6, 23%), rs6180 (Ex10, 42%), rs12521020 (In1, 32%), rs10941579 (In2, 32%), rs33972388 (In7, 37%), rs34223737 (In7, 1%), rs6880730 (In8, 5%), rs6182, rs6184 and rs115376349 (Ex10, 2%). In ISS, MAF distribution was not different from 41 control children or the HapMap database. We identified 4 heterozygous rare variants in 4/75 children (5.3%): p.R229H (Ex7) and p.R386C (Ex10) with normal IGF-I, IGFBP-3 and ALS levels, 1 of them with low GHBP (0.06). Conclusions: The sum of polymorphic variants has no effect on GH sensitivity, measured by levels of serum GHBP, IGF-I, IGFBP-3 and ALS. While p.R229H variant may result in a slight reduction in GHR expression as reflected by low GHBP levels, p.R386C, rs143475648 and c.618+700_705dupCAGCCA variants remain to be characterized by in vitro functional studies.