Growth Hormone Receptor Variants Research Articles

Reporting a novel growth hormone receptor gene variant in an Iranian consanguineous pedigree with Laron syndrome: a case report

BackgroundHuman growth hormone (hGH) plays a crucial role in growth by binding to growth hormone receptor (GHR) in target cells. Binding of GH molecules to their cognate receptors triggers downstream signaling pathways leading to the transcription of several genes, including insulin-like growth factor (IGF)-1. Pathogenic variants in the GHR gene can result in structural and functional defects in the GHR protein, leading to Laron Syndrome (LS) with the primary clinical manifestation of short stature. So far, around 100 GHR variants have been reported, mostly biallelic, as causing LS.Case presentationWe report on three siblings from an Iranian consanguineous family who presented with dwarfism. Whole-exome sequencing (WES) was performed on the proband, revealing a novel homozygous missense variant in the GHR gene (NM_000163.5; c.610 T > A, p.(Trp204Arg)) classified as a likely pathogenic variant according to the recommendation of the American College of Medical Genetics (ACMG). Co-segregation analysis was investigated using Sanger sequencing.ConclusionsTo date, approximately 400–500 LS cases with GHR biallelic variants, out of them 10 patients originating from Iran, have been described in the literature. Given the high rate of consanguineous marriages in the Iranian population, the frequency of LS is expected to be higher, which might be explained by undiagnosed cases. Early diagnosis of LS is very important, as treatment is available for this condition.

Characterization of dominant-negative growth hormone receptor variants reveals a potential therapeutic target for short stature.

Growth hormone insensitivity (GHI) encompasses growth restriction, normal/elevated growth hormone (GH), and low insulin-like growth factor I (IGF1). "Nonclassical" GHI is poorly characterized and is rarely caused by heterozygous dominant-negative (DN) variants located in the intracellular or transmembrane domains of the GH receptor (GHR). We sought to determine the molecular mechanisms underpinning the growth restriction in 2 GHI cases. A custom-made genetic investigative pipeline was exploited to identify the genetic cause of growth restriction in patients with GHI. Nanoluc binary technology (NanoBiT), in vitro splicing assays, western blotting, and flow cytometry, characterized the novel GHR variants. Novel heterozygous GHR variants were identified in 2 unrelated patients with GHI. In vitro splicing assays indicated both variants activated the same alternative splice acceptor site resulting in aberrant splicing and exclusion of 26 base pairs of GHR exon 9. The GHR variants produced truncated receptors and impaired GH-induced GHR signaling. NanoBiT complementation and flow cytometry showed increased cell surface expression of variant GHR homo/heterodimers compared to wild-type (WT) homodimers and increased recombinant human GH binding to variant GHR homo/heterodimers and GH binding protein (GHBP) cleaved from the variant GHRs. The findings demonstrated increased variant GHR dimers and GHBP with resultant GH sequestration. We identified and characterized 2 novel, naturally occurring truncated GHR gene variants. Intriguingly, these DN GHR variants act via the same cryptic splice acceptor site, highlighting impairing GH binding to excess GHBP as a potential therapeutic approach.

Assessment of Correlation of Growth Hormone Receptor Gene with Tooth Dimensions: A CBCT and Genotyping Study.

Aim:Assessment of root morphology, size, and amount of bone around tooth is essential before starting the orthodontic treatment. The present study aimed to assess the relationship between tooth dimensions with two gene variants of growth hormone (GH), namely rs6184 and rs6180.Materials and Methods:This study was conducted on 218 subjects (males: 104, females: 114) requiring orthodontic treatment. All underwent cone beam computed tomography (CBCT) scan for orthodontic treatment planning with Kodak CBCT machine. In all teeth, crown height (CH), root length (RL), and crown–root ratio were evaluated. Two growth hormone receptor (GHR) variants (rs6184 and rs6180) were genotyped using the TaqMan genotyping assay.Results:The mean CH and RL of all teeth, that is, maxillary and mandibular central incisors, lateral incisor, canine, first premolar, second premolar, first molar, and second molar, were measured. There was no significant difference in males and females (P > 0.05). Allele frequencies of GHR variants for rs6180 and rs6184 were 48.1% and 8.92%, respectively. Multiple regression analysis showed GHR rs6184 association with maxillary central incisor CH, maxillary canine RL, mandibular canine CH, and mandibular first premolar RL (P < 0.05).Conclusion:There was correlation of CH of maxillary and mandibular canine and RL of maxillary canine and mandibular first premolar with GHR rs6184.

Growth hormone receptor gene is related to root length and tooth length in human teeth.

To examine the relationship between tooth length and growth hormone receptor (GHR) gene variants in a healthy Japanese population. The subjects consisted of 193 Japanese adults (69 men, 124 women), aged 13 to 56 years. Genomic DNA was extracted from saliva and genotyped GHR rs6184 and rs6180 variants using the Taqman genotyping. Computed tomography (CT) images were acquired using a dental cone-beam CT scanner and reconstructed using open-source OsiriX medical image processing software. The maxillary (upper; U) and mandibular (lower, L) central incisors (1), lateral incisors (2), canines (3), first premolars (4), second premolars (5), first molars (6), and second premolars (7) were evaluated. Teeth were assessed for crown height (CH), root length (RL), overall tooth length (C+R), and crown to root ratio (C/R). The relationships between GHR variants and CH, RL, C+R, and C/R were statistically examined. The GHR variant rs6184 was associated with the root lengths and tooth length for the upper and lower lateral incisors and upper canines (U2 RL; U3 RL, C+R; L2 RL [ P < .05]). The results indicate that the GHR rs6184 variant is associated with tooth length and ratio dimensions in a Japanese cohort. Further studies utilizing a larger sample size are needed to confirm this finding.

Dynamic responses of prolactin, growth hormone and their receptors to hyposmotic acclimation in the olive flounder Paralichthys olivaceus

Prolactin (PRL) and growth hormone (GH) play important roles in regulating salt and water balance through osmoregulatory organs in vertebrates. The aim of this study was to investigate the dynamic changes of GH/PRL hormone gene expressions in the pituitary gland and their receptors in gill and kidney, as well as the plasma osmolality when the olive flounder fish Paralichthys olivaceus were acclimated in freshwater (FW) conditions. After transfer from seawater (SW) to freshwater (FW), the osmolality of FW-adaption fish reached the lowest level at 1d which rose slightly afterwards. However, the hormone gene expression of PRL increased from 2d, reaching its peak at 5d, and then decreased at 14d. At this time, the value was still significantly higher than the control, showing a similar trend to the plasma hormone PRL. In contrast, the pituitary mRNA level of GH significantly decreased at 1d and then returned to normal levels. The mRNA levels of PRL receptor (PRLR) in both gill and kidney displayed a similar trend to the pituitary PRL. We also observed the synchronous expression trend of the renal PRLR with pituitary PRL (5d) and the asynchronous expression peaks between branchial (8d) and renal PRLR (5d). Significant responses of GH and its receptor (GHR) in both gill and kidney during the FW-acclimation were not observed. Nevertheless, the gene expression of GH receptor variant (GHR-V) in both gill and kidney declined at 2d, indicating unknown osmoregulatory functions of GHR-V. Collectively, our results provided more insights of the PRL, GH and their corresponding receptors in modulating osmoregulatory responses, representing an important aspect of FW–acclimation in flounder fish.

Growth hormone receptor gene variant and three-dimensional mandibular morphology.

To examine the relationship between three-dimensional mandibular morphology and growth hormone receptor (GHR) gene variants in a healthy Japanese population. The subjects, who were unrelated Japanese orthodontic patients, consisted of 64 men and 114 women. Using the Taqman genotyping assay, GHR gene rs6184 and rs6180 variants were detected in genomic DNA extracted from saliva. Mandibular volume and length were measured from cone-beam computed tomography images that were analyzed using Analyze image-processing software. The relationship between GHR gene variants and three-dimensional mandibular morphology was statistically examined. Statistical significance for the relationship between the distance between the left and right coronoid processes and rs6180 was noted (P < .05). Our results indicate that the GHR variant rs6180 is associated with the distance between the left and right coronoid process in the Japanese subjects.

The growth hormone receptor gene deleted for exon three (GHRd3) polymorphism is associated with birth and placental weight

ContextHuman growth hormone receptor (GHR) transcripts have two isoforms, full-length (GHRfl) or exon 3 deleted (GHRd3). An association of these isoforms has been found with small for gestational age (SGA) infants but does not influence adult height. The role of this polymorphism in the birth size spectrum in the general population is unclear.ObjectiveTo determine the association of maternal and infants GHR exon 3 polymorphism with antenatal growth, birth size and early postnatal growth in two large, normal white European birth cohorts.Study designPregnant women from white European families were recruited by the University College London Foetal Growth Study (n = 774) and the Moore normal pregnancy cohort (n = 274). GHR variants, wild-type (fl) and deleted for exon 3 (d3) were analysed using multiplex PCR.ResultsThere was a significant underrepresentation of infants wild-type fl/fl (36%) and overrepresentation of d3/d3 (14%) genotypes in the SGA infants within the cohorts (χ2 = 11·2, P = 0·003, df = 2). Fl/fl was overrepresented in large for gestational age (LGA) infants (χ2 = 6·1, P = 0·047, df = 2). There was a significant association of infants GHR isoforms with placental weight (P < 0·001) and birth weight standard deviation scores (P = 0·04) with the fl/fl genotype associated with a larger placental and birth weight. In multiple regression analysis, the GHR isoform type, maternal booking weight and parity influenced placental weight (R2 = 0·35; P < 0·001, df = 7). The GHR isoform type was not related to antenatal anthropometric measurements or growth in infancy.ConclusionThese data suggest that the GHR isoforms are associated with placental and birth weight.

Growth Hormone Receptor Variants and Response to Pegvisomant in Monotherapy or in Combination with Somatostatin Analogs in Acromegalic Patients: A Multicenter Study

The influence of full-length GH receptor (GHR) and exon 3-deleted GHR (d3GHR) on responsiveness to pegvisomant (PEG-V) in acromegalic patients is uncertain. The aim of the study was to assess the distribution of GHR genotypes in a large series of patients on PEG-V therapy and their influence on treatment efficacy and adverse effects. A cross-sectional multicenter pharmacogenetic study was conducted in 16 Italian endocrinology centers of major universities and tertiary care hospitals. The study included 127 acromegalic patients enrolled from 2009 to 2010 not cured by previous surgery, radiotherapy, and long-acting somatostatin (SST) analogs, treated with PEG-V. Sixty-three of 127 patients received combined PEG-V + SST analog therapy. Clinical and hormonal data at diagnosis and before and during PEG-V therapy were inserted in a database. GHR exon 3 deletion and other polymorphisms were genotyped by the coordinator center. Differences in PEG-V dosage required for IGF-I normalization and occurrence of adverse effects between carriers and noncarriers of GHR variants were evaluated. d3GHR variants were not in Hardy-Weinberg equilibrium (P = 0.008). No association of these variants with PEG-V dose required for IGF-I normalization, adverse effects occurrence, and tumor regrowth was found in patients on PEG-V and on PEG-V + SST analog treatment. Similar data were obtained considering the GHR variant rs6180. This study did not confirm a better response of d3GHR to PEG-V treatment in acromegaly. Other studies are needed to determine whether deviation from Hardy-Weinberg equilibrium may indicate an association of d3GHR genotype with poor response to usual treatments.

Extreme Elevation of Serum Growth Hormone-Binding Protein Concentrations Resulting from a Novel Heterozygous Splice Site Mutation of the Growth Hormone Receptor Gene

Background/Aims: Circulating growth hormone-binding protein (GHBP), in humans, is the proteolytic product of the growth hormone receptor (GHR). We investigated a prepubertal male subject who was of short stature, but who had a markedly elevated serum level of GHBP. Methods: Serum and DNA from the patient and his mother were analyzed. Results: Both the patient and mother had serum GHBP concentrations over 100-fold higher than normal, by assays, and Western and ligand blot analysis. Sequencing of the GHR gene revealed a novel heterozygous C>A transversion at position 785-3 in the acceptor splice site of intron 7. Conclusion: In silico analysis of the altered sequence suggested that 785-3(C>A) is a splicing mutation, with either retention of intron 7 or the skipping of exon 8. The consequence is a truncated GHR lacking the transmembrane domain (encoded by exon 8) and the cytoplasmic domain. We hypothesize that this GHR variant cannot anchor to the cell membrane, and the continual secretion into the circulation explains the elevated levels of serum GHBP detected in the patient and his mother. Despite this mutation, the presence of the wild-type GHR allele, presumably, permits some normality in GH-induced action.

GHR exon 3 polymorphism: Association with type 2 diabetes mellitus and metabolic disorder

Growth hormone (GH) signaling via the growth hormone receptor (GHR) forms a major part of the GH-IGF-I axis, which is crucial for controlling metabolism and anabolism. Two common variants of the GHR differ by the presence (full length or GHR fl) or absence of exon 3 (exon 3 deleted or GHR d3), the function of which is unknown. However, differential response to GH treatment has been observed with carriers of the GHR d3 variant conferring a greater growth rate. This study investigates these GHR variants in subjects with normal glucose tolerance (NGT) and impaired glucose tolerance (IGT), including Type 2 diabetes mellitus (T2DM). DNA was extracted from blood samples from subjects with NGT ( n = 158), IGT ( n = 116) and T2DM ( n = 194). The T2DM subjects in set 1 ( n = 39) were newly diagnosed, whilst those in set 2 ( n = 155) had a mean duration of 7 years. Set 1 also included NGT and IGT subjects. Genotyping by standard PCR and gel electrophoresis were carried out. A significant difference was observed between T2DM and NGT ( p < 0.0001) with a significantly lower frequency of GHR d3 in T2DM (3.6% compared to 17% in NGT). Both sets of T2DM subjects with at least one GHR d3 allele had significantly higher BMI. In the larger subset of T2DM, GHR d3 was associated with higher CRP levels as well as age adjusted IGF-I, with a trend of higher C-peptide secretion and impaired lipid levels, indicating a phenotype with metabolic disorder when compared to the GHR fl/fl T2DM subjects. In conclusion, homozygosity for the GHR d3 allele appears to be preventive of T2DM. However, when other factors cause overt T2DM, the GHR d3 allele confers a phenotype indicative of metabolic disorder. This study supports the hypothesis that the two GHR alleles by their inclusion or exclusion of exon 3 are functionally different.

Molecular cloning and characterization of gilthead sea bream ( Sparus aurata) growth hormone receptor (GHR). Assessment of alternative splicing

The full-length growth hormone receptor (GHR) of gilthead sea bream ( Sparus aurata) was cloned and sequenced by RT-PCR and rapid amplification of 5′and 3′ends. The open reading frame codes for a mature 609 amino acid protein with a hydrophobic transmembrane region and all the characteristic motifs of GHRs. Sequence analysis revealed a 96 and 76% of amino acid identity with black sea bream ( Acanthopagrus schlegeli) and turbot ( Scophthalmus maximus) GHRs, respectively, but this amino acid identity decreases up to 52% for goldfish ( Carassius auratus) GHR. By means of real-time PCR assays, concurrent changes in the hepatic expression of GHRs and insulin-like growth factor-I (IGF-I) was evidenced. Moreover, their regulation occurred in conjunction with the summer spurt of growth rates and circulating levels of GH and IGF-I. Search of alternative splicing was carried out exhaustively for gilthead sea bream GHR, but Northern blot and 3′ RACE failed to demonstrate the occurrence of short alternative messengers. Besides, RT-PCR screening did not reveal deletions or insertions that could lead to alternative reading frames. In agreement with this, cross-linking assays only evidenced two protein bands that match well with the size of glycosylated and non-glycosylated forms of the full-length GHR. If so, it appears that alternative splicing at the 3′end does not occur in gilthead sea bream, although different messengers for truncated or longer GHR variants already exist in turbot and black sea bream, respectively. The physiological relevance of this finding remains unclear, but perhaps it points out large inter-species differences in the heterogeneity of the GHR population.

Reduced growth hormone receptor (GHR) messenger ribonucleic acid in liver of periparturient cattle is caused by a specific down-regulation of GHR 1A that is associated with decreased insulin-like growth factor I.

GH receptor (GHR) messenger RNA (mRNA) is transcribed from at least three different promoters within the liver of cattle. The first promoter (P1) is liver specific and alternatively splices exon 1A onto the GHR mRNA (GHR 1A mRNA). The second and third promoters (P2 and P3) have constitutive activity in many tissues and alternatively splice exons 1B and 1C onto the GHR mRNA (GHR 1B and GHR 1C mRNA). The total amount of GHR in the liver partially determines liver insulin-like growth factor I (IGF-I) synthesis in response to GH. Two studies were conducted to characterize the changes in GHR 1A mRNA, alternatively spliced GHR mRNA, and IGF-I mRNA during late pregnancy and early lactation in dairy cattle. Liver RNA was isolated from pregnant Holstein cattle (Bos taurus) on days -14, 0, and 21 relative to parturition (study 1) or days -14, 0, 15, 30, 60, and 90 relative to parturition (study 2). Ribonuclease protection assays were used to quantify total GHR (all GHR variants) as well as liver-specific GHR 1A and alternatively spliced GHR mRNA. Likewise, total IGF-I as well as alternatively spliced IGF-I mRNA (class 1 and class 2 transcripts) were measured. A decrease in total GHR mRNA at parturition (P < 0.01) was associated with a specific decrease in GHR 1A mRNA (P < 0.001). The amount of alternatively spliced GHR mRNA (including GHR 1B and GHR 1C mRNA) did not change at parturition (P > 0.10). Total liver IGF-I mRNA and blood IGF-I concentrations were also decreased at parturition (P < 0.05 and P < 0.01, respectively). However, a decrease in IGF-I mRNA was observed for both class 1 and class 2 IGF-I transcripts (P < 0.01 and P < 0.05, respectively). We conclude that the reduced amount of GHR mRNA during early lactation is caused by a specific down-regulation of GHR 1A mRNA that was associated with decreased liver IGF-I mRNA and decreased blood IGF-I concentrations. These data provide evidence for independent regulation of GHR mRNA by mechanisms that discriminate between GHR P1 (transcribes GHR 1A) and alternative promoters that transcribe constitutive GHR mRNA.