Genetic Analysis of GHR Should Contain Sequencing of All Coding Exons and Specific Intron Sequences, and Screening for Exon Deletions

Abstract

Background: The work-up of patients with clinical and/or biochemical features of growth hormone insensitivity (GHI) usually contains genetic analysis of the growth hormone receptor (GHR) gene, and if negative, of STAT5B, IGFALS and IGF1. In a previous report we described 2 siblings presenting with short stature, low IGF-1 levels, elevated GH secretion and no increase of IGF-1 after 1 week of GH administration. Repeated analysis of the GHR showed no abnormalities; however, further testing revealed a heterozygous STAT5B defect in both siblings. Subjects and Methods: Two boys of Surinam-Hindustan origin showed growth failure up to the age of 6-7 years, followed by partial catch-up growth associated with increasing body mass index. Reanalysis of GHR including published intronic sequences was performed on the patients' DNA collected 7 years earlier. Results: The heterozygous STAT5B variant proved to be functionally benign. A homozygous intronic mutation of the GHR, c.618+792A>G (IVS6+792A>G), was subsequently found, resulting in the activation of pseudoexon 6ψ, and explaining the GHI phenotype of the patients. Conclusion: An intronic GHR mutation should be considered in all patients with signs of GHI and no coding exon mutations, even if the phenotype is mild and even if other genetic variants have been found.

GHR gene transcript heterogeneity may explain phenotypic variability in GHR pseudoexon (6Ψ) patients

“…Unfortunately, we were unable to perform segregation studies as parental DNA was not available for any of the subjects. However, consistent with our findings, a previous study of two 6Ψ patients also demonstrated that other genetic variants did not contribute to the severity of the phenotypes (20).…”

“…Genotyping a region spanning 17.10 Mb around the GHR gene on chromosome 5 and analysis of the complex single polymorphic region in intron 9 of the GHR in five GHR 6Ψ families showed the same genotype for all affected members, suggesting the presence of a common ancestor (19). Furthermore, 19/22 of the known GHR pseudoexon patients are of Pakistani ethnicity (18,19,20,21). This implies that the GHR 6Ψ patient cohort share a common genetic background.…”

“…Milder or 'non-classical' GHI cases are being increasingly recognised owing to advent of next generation sequencing techniques and an increased awareness of this group of disorders. Other molecular defects of the GH-IGF1 axis that cause 'non-classical' or milder GHI phenotypes include dominant negative GHR (38,39,40,41) and STAT5B (42) gene mutations, heterozygous IGF1 (43,44,45), IGF2 (46,47) and IGFALS (48,49) mutations, homozygous PAPPA2 (6) mutations and the GHR pseudoexon (6Ψ) mutation (18,19,20,21). Non-classical GHI is an important clinical entity and the prevalence may be higher than classical GHI (2).…”

“…In 2007, an additional seven 6Ψ patients were reported with a wider range of short stature (SS) phenotypes (19). In 2013, Walenkamp et al described two further 6Ψ patients with growth failure followed by partial catch-up growth without treatment (20). We recently reported the spectrum of clinical and biochemical features in 20 6Ψ subjects, which included eleven previously reported individuals and nine additional patients (21).…”

Targeted Resequencing of Putative Growth-Related Genes Using Whole Exome Sequencing in Patients with Severe Primary IGF-I Deficiency

“…material, see www.karger.com/doi/10.1159/000480505). Furthermore, we sequenced a GHR pseudo-exon intronic mutation (c.618+792A>G) by routine Sanger sequencing, which in affected individuals leads to an in-frame insertion of 36 amino acid residues [8]. …”