GT repeat polymorphism in the 5' flanking region of the human growth hormone receptor gene

Sex-specific effects of a microsatellite polymorphism on human growth hormone receptor gene expression

Growth hormone (GH) binds to its specific receptor (GHR) at the surface of target cells activating multiple signaling pathways implicated in growth and metabolism. Dysregulation of GHRs leads to pathophysiological states that most commonly affect stature. We previously showed the association of a polymorphic (n = 15-37) GT microsatellite in the human GHR gene promoter with short stature in a sex-specific manner. In the present study we evaluated the functional relevance of this polymorphism in regulating GHR expression. Using luciferase reporter assays, we found that the GT repeat had a significant cis regulatory effect in response to HIF1α and a potential repressor role following C/EBPβ stimulation. Using a digital PCR application to measure allelic imbalance (AI), we showed a high prevalence of AI (∼76%) at the GHR locus in lymphoblastoid cell lines (LCLs), with a significantly higher degree of imbalance in LCLs derived from males. Examination of expression of GHR as well as other members of the GH-IGF1 axis in the LCLs revealed significant associations of GHR, IGF1 and BCL2 expression with GT genotype in a sex-specific manner. Our results suggest that this GT microsatellite exerts both cis and trans effects in a sex-specific context, revealing a new mechanism by which GHR gene expression is regulated.

Genetic variations at the human growth hormone receptor (GHR) gene locus are associated with idiopathic short stature

GH plays an essential role in the growing child by binding to the growth hormone receptor (GHR) on target cells and regulating multiple growth promoting and metabolic effects. Mutations in the GHR gene coding regions result in GH insensitivity (dwarfism) due to a dysfunctional receptor protein. However, children with idiopathic short stature (ISS) show growth impairment without GH or GHR defects. We hypothesized that decreased expression of the GHR gene may be involved. To test this, we investigated whether common genetic variants (microsatellites, SNPs) in regulatory regions of the GHR gene region were associated with the ISS phenotype. Genotyping of a GT‐repeat microsatellite in the GHR 5′UTR in a Montreal ISS cohort (n = 37 ISS, n = 105 controls) revealed that the incidence of the long/short (L/S) genotype was 3.3× higher in ISS children than controls (P = 0.04, OR = 3.85). In an Italian replication cohort (n = 143 ISS, n = 282 controls), the medium/short (M/S) genotype was 1.9× more frequent in the male ISS than controls (P = 0.017, OR = 2.26). In both ISS cohorts, logistic regression analysis of 27 SNPs showed an association of ISS with rs4292454, while haplotype analysis revealed specific risk haplotypes in the 3′ haploblocks. In contrast, there were no differences in GT genotype frequencies in a cohort of short stature (SS) adults versus controls (CARTaGENE: n = 168 SS, n = 207 controls) and the risk haplotype in the SS cohort was located in the most 5′ haploblock. These data suggest that the variants identified are potentially genetic markers specifically associated with the ISS phenotype.

Genetic polymorphisms and protein structures in growth hormone, growth hormone receptor, ghrelin, insulin-like growth factor 1 and leptin in Mehraban sheep

The somatotropic axis, the control system for growth hormone (GH) secretion and its endogenous factors involved in the regulation of metabolism and energy partitioning, has promising potentials for producing economically valuable traits in farm animals. Here we investigated single nucleotide polymorphisms (SNPs) of the genes of factors involved in the somatotropic axis for growth hormone (GH1), growth hormone receptor (GHR), ghrelin (GHRL), insulin-like growth factor 1 (IGF-I) and leptin (LEP), using polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and DNA sequencing methods in 452 individual Mehraban sheep. A nonradioactive method to allow SSCP detection was used for genomic DNA and PCR amplification of six fragments: exons 4 and 5 of GH1; exon 10 of GH receptor (GHR); exon 1 of ghrelin (GHRL); exon 1 of insulin-like growth factor-I (IGF-I), and exon 3 of leptin (LEP). Polymorphisms were detected in five of the six PCR products. Two electrophoretic patterns were detected for GH1 exon 4. Five conformational patterns were detected for GH1 exon 5 and LEP exon 3, and three for IGF-I exon 1. Only GHR and GHRL were monomorphic. Changes in protein structures due to variable SNPs were also analyzed. The results suggest that Mehraban sheep, a major breed that is important for the animal industry in Middle East countries, has high genetic variability, opening interesting prospects for future selection programs and preservation strategies.

Characterization of the GHR gene genetic variation in Chinese indigenous goat breeds

The aim of the present work was to investigate single nucleotide polymorphism (SNP) of growth hormone receptor (GHR) gene exon 10, characterize the genetic variation in three Chinese indigenous goat breeds, and search for its potential association with cashmere traits. In this study, a polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) protocol has been developed for rapid genotyping of the GHR gene in goats. One hundred seventy-eight goats from Liaoning Cashmere (96), Inner Mongolia White Cashmere (40), and Chengdu Grey (42) breeds in China were genotyped at GHR locus using the protocol developed. In all goat breeds investigated, a SNP in exon 10 of GHR gene has been identified by analyzing genomic DNA. The polymorphism consists of a single nucleotide substitution A → G, resulting in two alleles named, respectively, A and G based on the nucleotide at the position. The allele A was found to be more common in the animals investigated, and seems to be more consistent with cattle and zebu at this polymorphic site found in goats. The Hardy-Weinberg equilibrium of genotype distributions of GHR locus was verified in Liaoning Cashmere, and Inner Mongolia White Cashmere breeds. According to the classification of polymorphism information content (PIC), Chengdu Grey was less polymorphic than Liaoning Cashmere and Inner Mongolia White Cashmere breeds at this locus. The phylogenetic tree of different species based on the nucleotide sequences of GHR gene exon 10 is generally in agreement with the known species relationship. No significant association was found between the polymorphism revealed and the cashmere traits analyzed in present work.

The cytoplasmic C2A domain of synaptotagmin shows sequence specific interaction with its own mRNA

Synaptotagmin-1 (Syt1) is essential in Ca(2+)-dependent neurotransmitter release, but its expression regulation is unknown. Here we report that the cytoplasmic Syt1 fragment forms ribonucleoprotein complex by interacting with the 3' untranslated region (3(')UTR) of its own mRNA. Two protein-binding domains, GU(15) repeat and GUCAAUG, within the Syt 3'UTR and the C2 domains in Syt1, especially C2A, are essential in this ribonucleoprotein complex formation. Furthermore, in in vitro assay the translation efficiency of Syt1 mRNA was downregulated in presence of 3'UTR. These results demonstrate for the fist time that the soluble fraction of Syt1 can interact with its own mRNA in a highly sequence specific manner.

Transcribed short tandem repeats occur in couples with strongly preferred registers

Short tandem repeats (STRs) have been widely observed, but most STRs have no recognized organization or function. Here we show that for diverse mRNAs, 84% of (GC)(n) repeats were found unexpectedly coupled with another STR, (GU)(n). These STR couples exhibited preferred polarity and register. In 3(') untranslated mRNA sequences (UTRs) 100% of (GC)(n>6) repeats were tightly coupled with (GU)(n). For (GC)(n), stem folding energy correlated with the length and number of neighboring, non-folding (GU)(n) partners (p=0.014). Approximately 20% of (AU)(n>/=14) repeats were coupled with (GU)(n). The STR couple (AC)(n)(AG)(n) also exhibited polarity and register preferences. The sequence arrangement at STR-couple joints was conserved rigorously, suggesting that these sequences were under selection pressure. Some STR couples may function as mRNA processing landmarks, based on alternative transcript comparisons. These observations suggest that some transcribed STRs may be functional UTR signals with predictable organization and usage patterns.