Growth Hormone Receptor Mutation Research Articles

6459 A Novel Long-Acting GH Receptor Antagonist Optimizing Therapeutic Efficacy and Duration

Abstract Disclosure: C. Ku: None. C. Kang: None. J. Oh: None. E. Wang: None. H. Song: None. K. Park: None. B. Kim: None. K. Kim: None. S. You: None. S. Park: None. E. Lee: None. Background: Forty to sixty percent of acromegalic patients undergo medical treatment, utilizing somatostatin analogues, dopamine agonists, and GH receptor (GHR) antagonists. The GHR antagonist, pegvisomant exhibits the most robust efficacy in reducing IGF-1 levels in acromegalic patients. However, pegvisomant faces several clinical limitations, such as poor compliance due to the necessity of daily injections. This study aimed to develop a novel, long-acting fusion GHR antagonist with optimized therapeutic efficacy and duration. Method: Twelve mutant proteins with alterations in the C-terminal and N-terminal regions of GHR were generated to confirm the GHR binding affinity and inhibitory potency compared with pegvisomant, which was evaluated with STAT5b luciferase reporter assay. Several carriers were engineered into selected mutant GHRs to increase the therapeutic duration. For in vivo experiments, single or repetitive injection of GHR antagonists were applied to acromegalic mouse model (somatotroph specific Aip knock out (sAIPKO) mice). Pharmacokinetics (PK) and pharmacodynamics (PD) were evaluated in New Zealand White (NZW) rabbits. Result: Four out of the 12 GHR mutants exhibited higher affinity and stronger inhibitory potency toward human GHR when compared to pegvisomant. Specifically, three GHR mutants significantly reduced serum IGF-1 levels in sAIPKO mice following daily injections of 20 mg/kg for 7 days (52.3±6.0 to 5.9±1.3, 50.3±3.5 to 32.3±2.3, and 49.8±3.7 to 13.9±4.3 ng/mL; all p < 0.05). Among them, S4020N exhibited the lowest EC50 value for GHR binding affinity in in vitro analysis containing human GHR (0.594 nM) and mouse GHR (0.891 nM). Following fusion with each long-acting carrier, S4020N with the Fc carrier protein (ALT-B5) demonstrated the highest binding affinity and the strongest inhibitory potency toward human GHR, surpassing pegvisomant by 14 and 25 times, respectively. Administration of ALT-B5 (80 mg/kg) and pegvisomant (24 mg/kg) at a 3-day interval revealed the superior efficacy of ALT-B5 over pegvisomant (1879±219.4 vs. 3800±355.9 ng*hr/mL IGF-1 AUC for 5 days in ALT-B5 and pegvisomant, respectively; p < 0.01). In PK/PD studies, ALT-B5 was administered at doses of 3 mg/kg and 10 mg/kg in NZW rabbits, and PK/PD parameters were compared with the same molar concentration of pegvisomant. ALT-B5 exhibited the longest therapeutic duration and the highest efficacy compared to pegvisomant. Conclusion: ALT-B5 exhibited the longest duration and highest effectiveness in lowering IGF-1 levels. ALT-B5 emerges as a potential novel therapeutic option for acromegaly. Presentation: 6/1/2024

Genome editing of porcine zygotes via lipofection of two guide RNAs using a CRISPR/Cas9 system.

CRISPR/Cas9-based multiplex genome editing via electroporation is relatively efficient; however, lipofection is versatile because of its ease of use and low cost. Here, we aimed to determine the efficiency of lipofection in CRISPR/Cas9-based multiplex genome editing using growth hormone receptor (GHR) and glycoprotein alpha-galactosyltransferase 1 (GGTA1)-targeting guide RNAs (gRNAs) in pig zygotes. Zona pellucida-free zygotes were collected 10 h after in vitro fertilization and incubated with Cas9, gRNAs, and Lipofectamine 2000 (LP2000) for 5 h. In Experiment 1, we evaluated the mutation efficiency of gRNAs targeting either GHR or GGTA1 in zygotes transfected using LP2000 and cultured in 4-well plates. In Experiment 2, we examined the effects of the culture method on the development, mutation rate, and mutation efficiency of zygotes with simultaneouslydouble-edited GHR and GGTA1, cultured using 4-well (group culture) and 25-well plates (individual culture). In Experiment 3, we assessed the effect of additional GHR-targeted lipofection before and after simultaneous double gRNA-targeted lipofection on the mutation efficiency of edited embryos cultured in 25-well plates. No significant differences in mutation rates were observed between the zygotes edited with either gRNA. Moreover, the formation rate of blastocysts derived from GHR and GGTA1 double-edited zygotes was significantly increased in the 25-well plate culture compared to that in the 4-well plate culture. However, mutations were only observed in GGTA1 when zygotes were transfected with both gRNAs, irrespective of the culture method used. GHR mutations were detected only in blastocysts derived from zygotes subjected to GHR-targeted lipofection before simultaneous double gRNA-targeted lipofection. Overall, our results suggest that additional lipofection before simultaneous double gRNA-targeted lipofection induces additional mutations in the zygotes.

A Clinical Trial of High Dose Growth Hormone in a Patient with a Dominant Negative Growth Hormone Receptor Mutation.

Rare patients with short stature and growth hormone (GH) resistance have dominant-negative variants in the GH receptor. We describe a patient with GH resistance due to elevated levels of GH binding protein and demonstrate the potential for a precision medicine intervention. To determine whether high dose GH can overcome GH resistance in this specific patient resulting in normal IGF-1 levels and improved growth rates. Single patient trial of ascending doses of GH followed by dose stable phase; total 12 months of treatment. Patient has a heterozygous variant in GH receptor resulting in elevated levels of GH binding protein manifesting as GH resistance and severe short stature. Daily subcutaneous GH starting at 50 micrograms/kg/day and escalating to 250 micrograms/kg/day until goal IGF-1 achieved. Subject continued 250 micrograms/kg/day for a total treatment duration of 12 months. The primary outcome measure was the dose of GH required to achieve an IGF-1 level above the mid-point of the normal range. Secondary endpoints included height velocity and the change in height SDS during the 1st year of treatment. A dose of GH of 250 micrograms/kg/day achieved the target IGF-1 level. The patient's annualized height velocity was 8.7 cm/year, an increase of 3.4 cm/year from baseline, resulting in a 0.81 SD gain in height. A precision medicine approach of extremely high dose GH was able to overcome GH resistance in a patient with a dominant-negative variant in the GH receptor resulting in elevated GH binding protein levels.

Cancer in growth hormone excess and growth hormone deficit.

The relationship between growth hormone (GH) excess and cancer is a controversial matter. Until 2016, most studies in patients with acromegaly found links with colon and thyroid neoplasms. However, recent studies found increased risks in gastric, breast, and urinary tract cancer also. Concordantly, clinical situations where GH and insulin-like growth facto-I deficits exist are indeed associated with diminished malignancy incidence. In line with these observations, gain-of-function mutations of various enzymes belonging to the GH and IGF-I signaling pathways have been associated with increased carcinogenesis; similarly, loss-of-function mutations of other enzymes that usually work as tumor repressors are also associated with augmented cancer risk. In a study performed in Ecuador, it was demonstrated that subjects in the Ecuadorian cohort with Laron syndrome (ELS), who have a mutant GH receptor and greatly diminished GH and IGF-I signaling, display diminished incidence of cancer. Along with absent action of GH and IGF-I, ELS individuals also have low serum insulin levels and decreased insulin resistance. Furthermore, hyperglycemia and hyperinsulinemia are indispensable for fast cell mitosis, including that of those cells present in the benign and malignant neoplasms. Notably, and despite their obesity, subjects with the ELS display normoglycemia and hypo-insulinemia, along with diminished incidence of malignancies. We believe that the dual low-IGF-I/low insulin serum levels are responsible for the cancer protection, especially considering that the insulin/INSR signaling is a central site for energy generation in the form of ATP and GDP, which are indispensable for all and every GH/IGF-I physiologic as well as pathologic events.

GHR disruption in mature adult mice alters xenobiotic metabolism gene expression in the liver.

Lifelong reduction of growth hormone (GH) action extends lifespan and improves healthspan in mice. Moreover, congenital inactivating mutations of GH receptor (GHR) in mice and humans impart resistance to age-associated cancer, diabetes, and cognitive decline. To investigate the consequences of GHR disruption at an adult age, we recently ablated the GHR at 6-months of age in mature adult (6mGHRKO) mice. We found that both, male and female 6mGHRKO mice have reduced oxidative damage, with males 6mGHRKO showing improved insulin sensitivity and cancer resistance. Importantly, 6mGHRKO females have an extended lifespan compared to controls. To investigate the possible mechanisms leading to health improvements, we performed RNA sequencing using livers from male and female 6mGHRKO mice and controls. We found that disrupting GH action at an adult age reduced the gap in liver gene expression between males and females, making gene expression between sexes more similar. However, there was still a 6-fold increase in the number of differentially expressed genes when comparing male 6mGHRKO mice vs controls than in 6mGHRKO female vs controls, suggesting that GHR ablation affects liver gene expression more in males than in females. Finally, we found that lipid metabolism and xenobiotic metabolism pathways are activated in the liver of 6mGHRKO mice. The present study shows for the first time the specific hepatic gene expression profile, cellular pathways, biological processes and molecular mechanisms that are driven by ablating GH action at a mature adult age in males and females. Importantly, these results and future studies on xenobiotic metabolism may help explain the lifespan extension seen in 6mGHRKO mice.

An Attempt to Identify the Medaka Receptor for Somatolactin Alpha Using a Reverse Genetics Approach.

Somatolactin alpha (SLα) is a fish-specific hormone involved in body color regulation. The growth hormone (GH) is another hormone that is expressed in all vertebrates and promotes growth. These peptide hormones act by binding to receptors (SLα receptor (SLR) and GH receptor (GHR)); however, the relationships between these ligands and their receptors vary among species. Here, we first performed phylogenetic tree reconstruction by collecting the amino-acid sequences classified as SLR, GHR, or GHR-like from bony fish. Second, we impaired SLR or GHR functions in medaka (Oryzias sakaizumii) using CRISPR/Cas9. Lastly, we analyzed SLR and GHR mutants for phenotypes to deduce their functions. Phylogenetic tree reconstruction was performed using a total of 222 amino-acid sequences from 136 species, which revealed that many GHRa and GHRb are vaguely termed as GHR or GHR-like, while showing no orthologous/paralogous relationships. SLR and GHR mutants were successfully established for phenotyping. SLR mutants exhibited premature lethality after hatching, indicating an essential role for SLR in normal growth. GHR mutations did not affect viability, body length, or body color. These results provide no evidence that either SLR or GHR functions as a receptor for SLα; rather, phylogenetically and functionally, they seem to be receptors for GH, although their (subfunctionalized) roles warrant further investigation.

Conditional gene regulation models demonstrate a pro-proliferative role for growth hormone receptor in prostate cancer.

Humans with inactivating mutations in growth hormone receptor (GHR) have lower rates of cancer, including prostate cancer. Similarly, mice with inactivating Ghr mutations are protected from prostatic intraepithelial neoplasia in the C3(1)/TAg prostate cancer model. However, gaps in clinical relevance in those models persist. The current study addresses these gaps and the ongoing role of Ghr in prostate cancer using loss-of-function and gain-of-function models. Conditional Ghr inactivation was achieved in the C3(1)/TAg model by employing a tamoxifen-inducible Cre and a prostate-specific Cre. In parallel, a transgenic GH antagonist was also used. Pathology, proliferation, and gene expression of 6-month old mouse prostates were assessed. Analysis of The Cancer Genome Atlas data was conducted to identify GHR overexpression in a subset of human prostate cancers. Ghr overexpression was modeled in PTEN-P2 and TRAMP-C2 mouse prostate cancer cells using stable transfectants. The growth, proliferation, and gene expression effects of Ghr overexpression was assessed in vitro and in vivo. Loss-of-function for Ghr globally or in prostatic epithelial cells reduced proliferation and stratification of the prostatic epithelium in the C3(1)/TAg model. Genes and gene sets involved in the immune system and tumorigenesis, for example, were dysregulated upon global Ghr disruption. Analysis of The Cancer Genome Atlas revealed higher GHR expression in human prostate cancers with ERG-fusion genes or ETV1-fusion genes. Modeling the GHR overexpression observed in these human prostate cancers by overexpressing Ghr in mouse prostate cancer cells with mutant Pten or T-antigen driver genes increased proliferation of prostate cancer cells in vitro and in vivo. Ghr overexpression regulated the expression of multiple genes oppositely to Ghr loss-of-function models. Loss-of-function and gain-of-function Ghr models, including prostatic epithelial cell specific alterations in Ghr, altered proliferation, and gene expression. These data suggest that changes in GHR activity in human prostatic epithelial cells play a role in proliferation and gene regulation in prostate cancer, suggesting the potential for disrupting GH signaling, for example by the FDA approved GH antagonist pegvisomant, may be beneficial in treating prostate cancer.

Mutations in GHR and IGF1R Genes as a Potential Reason for the Lack of Catch-Up Growth in SGA Children.

The aim of this review was to describe all of the mutations in the growth hormone receptor (GHR) and insulin-like growth factor-1 receptor (IGF1R) genes that have been discovered so far, and their possible impact on final body height, as well as their relationship with catch-up growth in children born small for gestational age (SGA). Mutations in the GHR gene were found to cause a body height below −2 SD, from the mean for sex and age, whereas the mutations in the IGF1R gene were associated with low body height and intrauterine growth restriction (IUGR), and with being born SGA. After birth, when the child’s growth is not restricted by the intrauterine environment, the infant may develop its developmental potential and experience catch-up growth, which makes it possible to catch up with peers born appropriate for gestational age (AGA). Despite this, catch-up growth does not apply to all, but only to about 85% of SGA children, and its mechanism is unknown. It is possible that SGA children who did not experience catch-up growth are carriers of mutations in the GHR and/or IGF1R genes

Associations of SNPs in GHR gene with growth and milk yield of Anatolian buffaloes

This study was carried out to investigate the associations between single nucleotide polymorphisms (SNP) in the growth hormone receptor (GHR) gene and growth and milk yields of Anatolian buffaloes. Growth records of genotyped 3012 Anatolian buffaloes and 467 lactations of 329 cows from them were used. The overall means of weights at birth, six and 12 months of ages and lactation milk yield were 29.377 ± 0.342 kg, 96.15 ± 1.48 kg, 165.54 ± 2.18 kg, and 976.3 ± 39.9 kg, respectively. Three mutations (g.31601787 G > A, g.31601784 G > A, and g.31601783 G > del) in GHR were detected. A least-squares analysis was carried out to determine the fixed effects of some environmental factors and these SNPs. The g.31601784 G > A mutation had a significant (p < 0.05) effect on weights at 12 months of age. The cows with GG genotype in the location of g.31601783 were superior (p < 0.05) in milk production. These results indicate that the SNP markers in the GHR gene could be associated with economically important traits and provide some advantages to breeders for the selection of buffaloes in early age.

Systemic Deficiency of GHR in Pigs leads to Hepatic Steatosis via Negative Regulation of AHR Signaling.

Laron syndrome (LS) is an autosomal recessive genetic disease mainly caused by mutations in the human growth hormone receptor (GHR) gene. Previous studies have focused on Ghr mutant mice, but compared with LS patients, Ghr knockout (KO) mice exhibit differential lipid metabolism. To elucidate the relationship between GHR mutation and lipid metabolism, the role of GHR in lipid metabolism was examined in GHR KO pigs and hepatocytes transfected with siGHR. We observed high levels of free fatty acids and hepatic steatosis in GHR KO pigs, which recapitulates the abnormal lipid metabolism in LS patients. RNAseq analysis revealed that genes related to the fatty acid oxidation pathway were significantly altered in GHR KO pigs. AHR, a transcription factor related to lipid metabolism, was significantly downregulated in GHR KO pigs and siGHR-treated human hepatocytes. We found that AHR directly regulated fatty acid oxidation by directly binding to the promoters of ACOX1 and CPT1A and activating their expression. These data indicate that loss of GHR disturbs the ERK-AHR-ACOX1/CPT1A pathway and consequently leads to hepatic steatosis. Our results established AHR as a modulator of hepatic steatosis, thereby providing a therapeutic target for lipid metabolism disorder.

Laron Syndrome—Possibilities of Diagnoses, Treatment, and Outcome

Background&#x0D; Laron syndrome (growth hormone insensitivity) is a rare autosomal recessive condition characterized by severe short stature with postnatal onset usually (1), particular facial features and hypoglycemia in childhood, and type 2 diabetes mellitus, dyslipidemia, metabolic syndrome, and obesity in adulthood (2), caused by growth hormone receptor (GHR) anomalies (insensitivity). It is estimated that there are 350 people with this condition worldwide (3). The growth hormone receptor mutation prevents the stimulating effects of growth hormone, inducing insulin-like growth factor-1 (IGF1) deficiency. Treatment with recombinant IGF1, the only treatment option which can improve final height (4), is not available for all patients. &#x0D; Aim&#x0D; Present the clinical outcomes of a Laron syndrome patient untreated and on hormonal substitution treatment.&#x0D; Case Report&#x0D; A 18-year-old girl with Laron syndrome diagnosed at the age of 2 years and 10 months, based on the clinical feature of severe short stature (height—63 cm; −8.24 SDS, standard deviation score), particular facial features (protruding forehead, saddle nose, large eyes, sparse and thin silky hair, and high-pitched voice), small hands and feet, and sweating and hypotonic episodes, especially in the morning. The endocrine growth axis assessment revealed an elevated growth hormone concentration (&gt;40 ng/mL; 0–8 ng/mL) and very low serum IGF-1 levels ( A L141X) in the 6 exon of the GHR gene. The growth velocity without hormonal substitution was low at 0.23 cm/month (14.5 cm/63 months). After 15 months (between 8 years 1 month and 9 years 4 months) of IGF1 (mecasermin) treatment, the growth velocity increased to 0.53 cm/month, the girl’s height increased from 77.5 cm (−8.55 SDS) to 85.6 cm (−7.94 SDS). After IGF1 treatment discontinuation, height velocity fell to 0.22 cm/month. At the age of 17 years and 2 months, hormone replacement therapy with mecasermin was resumed up to 18 years. The patient also had associated pubertal delay; thelarche started at the age of 15 and progressed slowly. The final height of the patient was 117 cm. In addition, she has developed focal epilepsy, obesity, and depression.&#x0D; Conclusions&#x0D; Early diagnosis and hormone substitution therapy may reduce the clinical consequences of complications, improving the prognosis.

195-LB: Metabolomic Characterization of Laron and Guevara-Rosenbloom Syndromes Using UHPLC-HRMS

Laron syndrome (LS) is a rare autosomal recessive growth hormone (GH) insensitivity condition due to GH receptor mutation, and with phenotypic features likened to GH deficiency. The incidence of LS in Ecuador is very high and has gained worldwide attention due to its low incidence of cancer and diabetes mellitus. A more recently described population is affected with “Guevara-Rosenbloom syndrome” (GRS). While both groups exhibit severe short stature (-4 to -12 SDS), GRS subjects have normal GH signaling and responses and, unlike LS, have intrauterine growth retardation and early onset type 2 diabetes (T2DM). Since both groups have diminished insulin secretion, there is a unique opportunity to investigate their metabolome under each specific disease. Levels of certain amino acids in insulin-resistant (IR) states such as T2DM are distinct and special attention has been given to the predicting power of branched chain and aromatic amino acids, carnitines, and free fatty acids for IR and T2DM risk assessment. Our aim was to understand the metabolic differences between LS and GRS, which both have diminished insulin secretion but different GH counter-regulation as well as to compare these groups to normal controls. The metabolome of these 3 cohorts was assessed at the following instances: a) At the fasting state, and b) After an oral challenge of 1.5 mg/kg of glucose per kilogram of body weight, administered immediately after the fasting sample was drawn (samples were taken every 30 minutes for 5 hours [5h]). Preliminary results (by ANOVA) show a strong correlation, in the fasting state, between the control and the LS groups with clear discrimination from the GRS cohort, as determined by a heatmap of the top 100 features. Furthermore, the analysis of the 5h profile after the glucose challenge in the 3 groups revealed significant correlations in the levels of amino-acids that have been related to the genesis of IR and T2DM. This work represents the first deep-metabolome analysis in this unique study group. Disclosure V. Rubio: None. C.A. Chamberlain: None. C. Wasserfall: None. J. Guevara-Aguirre: None. A. Guevara: None. A.L. Rosenbloom: None. M.A. Atkinson: None. R.A. Yost: None. T.J. Garrett: None. Funding National Institutes of Health (U24DK097209)

Growth Hormone insensitivity (Laron syndrome): Report of a new family and review of Brazilian patients.

Laron’s syndrome (LS) is a rare genetic disorder characterized by insensitivity to growth hormone (GH). Up to the present time, over 70 mutations of GH receptor (GHR) gene have been identified leading to GH/insulin-like growth factor type 1 (IGF1) signaling pathway defect. The number of LS patients worldwide is unknown, as many are probably undiagnosed. We report two sibs from a consanguineous family from Minas Gerais, southeastern Brazil. The parents have three children. The older, a 4-years-old girl was 80.2 cm tall (-5.7 SDS height/age), and the youngest sister, aged 3 years, was 73.2 cm tall (-5.82 SDS height/age). Their clinical and biochemical features are typical of LS patients, such as high serum level of GH and low IGF1 concentrations. A homozygous c.1A>T nucleotide substitution in GHR exon 2 in the probands’ samples was identified. Their parents and healthy sister are heterozygous for the same variant that abolishes the translation initiation codon of GHR. This mutation has not been reported in Brazilian patients and was previously associated with an LS phenotype in a single 29-year-old Spanish man. In addition to this case report, we summarize the main characteristics and molecular data of the 21 LS Brazilian patients who have been published to date.

Growth Hormone Receptor Mutations Related to Individual Dwarfism.

Growth hormone (GH) promotes body growth by binding with two GH receptors (GHRs) at the cell surface. GHRs interact with Janus kinase, signal transducers, and transcription activators to stimulate metabolic effects and insulin-like growth factor (IGF) synthesis. However, process dysfunctions in the GH–GHR–IGF-1 axis cause animal dwarfism. If, during the GH process, GHR is not successfully recognized and/or bound, or GHR fails to transmit the GH signal to IGF-1, the GH dysfunction occurs. The goal of this review was to focus on the GHR mutations that lead to failures in the GH–GHR–IGF-1 signal transaction process in the dwarf phenotype. Until now, more than 90 GHR mutations relevant to human short stature (Laron syndrome and idiopathic short stature), including deletions, missense, nonsense, frameshift, and splice site mutations, and four GHR defects associated with chicken dwarfism, have been described. Among the 93 identified mutations of human GHR, 68 occur extracellularly, 13 occur in GHR introns, 10 occur intracellularly, and two occur in the transmembrane. These mutations interfere with the interaction between GH and GHRs, GHR dimerization, downstream signaling, and the expression of GHR. These mutations cause aberrant functioning in the GH-GHR-IGF-1 axis, resulting in defects in the number and diameter of muscle fibers as well as bone development.

Phenotypic spectrum and responses to recombinant human IGF1 (rhIGF1) therapy in patients with homozygous intronic pseudoexon growth hormone receptor mutation.

Patients with homozygous intronic pseudoexon GH receptor (GHR) mutations (6Ψ) have growth hormone insensitivity (GHI) (growth failure, IGF1 deficiency and normal/elevated serum GH). We report 9 patients in addition to previously described 11 GHR 6Ψ patients and their responses to rhIGF1 therapy. 20 patients (12 males, 11 families, mean age 4.0 ± 2.2 years) were diagnosed genetically in our centre. Phenotypic data and responses to rhIGF1 treatment were provided by referring clinicians. Continuous parametric variables were compared using Student t-test or ANOVA. 10/20 (50%) had typical facial features of GHI, 19/20 (95%) from consanguineous families and 18/20 (90%) of Pakistani origin. At diagnosis, mean height SDS: -4.1 ± 0.95, IGF1 SDS: -2.8 ± 1.4; IGFBP3 SDS: -3.0 ± 2.1 and mean basal and peak GH levels: 11.9 µg/L and 32.9 µg/L, respectively. 1/12 who had IGF1 generation test, responded (IGF1: 132-255 ng/mL). 15/20 (75%; 11M) received rhIGF1 (mean dose: 114 µg/kg twice daily, mean duration: 5.3 ± 2.5 years). Mean baseline height velocity of 4.7 ± 1.1 cm/year increased to 7.4 ± 1.8 cm/year (P = 0.001) during year 1 of therapy. Year 3 mean height SDS (-3.2 ± 1.0) was higher than pre-treatment height SDS (-4.3 ± 0.8) (P = 0.03). Mean cumulative increase in height SDS after year 5 was 1.4 ± 0.9. Difference between target height (TH) SDS and adult or latest height SDS was less than that of TH SDS and pre-treatment height SDS (2.1 ± 1.2 vs 3.0 ± 0.8; P = 0.02). In addition to phenotypic heterogeneity in the cohort, there was mismatch between clinical and biochemical features in individual patients with 6Ψ GHR mutations. rhIGF1 treatment improved height outcomes.

Phenotypic spectrum and response to recombinant human IGF1(rhIGF1) therapy in patients with homozygous intronic pseudoexon (6Ψ)GH receptor mutations

Phenotypic spectrum and response to recombinant human IGF1(rhIGF1) therapy in patients with homozygous intronic pseudoexon (6Ψ)GH receptor mutations

Let-7b Regulates Myoblast Proliferation by Inhibiting IGF2BP3 Expression in Dwarf and Normal Chicken.

The sex-linked dwarf chicken is caused by the mutation of growth hormone receptor (GHR) gene and characterized by shorter shanks, lower body weight, smaller muscle fiber diameter and fewer muscle fiber number. However, the precise regulatory pathways that lead to the inhibition of skeletal muscle growth in dwarf chickens still remain unclear. Here we found a let-7b mediated pathway might play important role in the regulation of dwarf chicken skeletal muscle growth. Let-7b has higher expression in the skeletal muscle of dwarf chicken than in normal chicken, and the expression of insulin-like growth factor 2 mRNA binding protein 3 (IGF2BP3), which is a translational activator of IGF2, showed opposite expression trend to let-7b. In vitro cellular assays validated that let-7b directly inhibits IGF2BP3 expression through binding to its 3′UTR region, and the protein level but not mRNA level of IGF2 would be reduced in let-7b overexpressed chicken myoblast. Let-7b can inhibit cell proliferation and induce cell cycle arrest in chicken myoblast through let-7b-IGF2BP3-IGF2 signaling pathway. Additionally, let-7b can also regulate skeletal muscle growth through let-7b-GHR-GHR downstream genes pathway, but this pathway is non-existent in dwarf chicken because of the deletion mutation of GHR 3′UTR. Notably, as the loss binding site of GHR for let-7b, let-7b has enhanced its binding and inhibition on IGF2BP3 in dwarf myoblast, suggesting that the miRNA can balance its inhibiting effect through dynamic regulate its binding to target genes. Collectively, these results not only indicate that let-7b can inhibit skeletal muscle growth through let-7b-IGF2BP3-IGF2 signaling pathway, but also show that let-7b regulates myoblast proliferation by inhibiting IGF2BP3 expression in dwarf and normal chickens.

Novel Dominant-Negative GH Receptor Mutations Expands the Spectrum of GHI and IGF-I Deficiency.

Context:Autosomal-recessive mutations in the growth hormone receptor (GHR) are the most common causes for primary growth hormone insensitivity (GHI) syndrome with classical GHI phenotypically characterized by severe short stature and marked insulin-like growth factor (IGF)-I deficiency. We report three families with dominant-negative heterozygous mutations in the intracellular domain of the GHR causing a nonclassical GHI phenotype.Objective:To determine if the identified GHR heterozygous variants exert potential dominant-negative effects and are the cause for the GHI phenotype in our patients.Results:All three mutations (c.964dupG, c.920_921insTCTCAAAGATTACA, and c.945+2T>C) are predicted to result in frameshift and early protein termination. In vitro functional analysis of variants c.964dupG and c.920_921insTCTCAAAGATTACA (c.920_921ins14) suggests that these variants are expressed as truncated proteins and, when coexpressed with wild-type GHR, mimicking the heterozygous state in our patients, exert dominant-negative effects. Additionally, we provide evidence that a combination therapy of recombinant human growth hormone (rhGH) and rhIGF-I improved linear growth to within normal range for one of our previously reported patients with a characterized, dominant-negative GHR (c.899dupC) mutation.Conclusion:Dominant-negative GHR mutations are causal of the mild GHI with substantial growth failure observed in our patients. Heterozygous defects in the intracellular domain of GHR should, therefore, be considered in cases of idiopathic short stature and IGF-I deficiency. Combination therapy of rhGH and rhIGF-I improved growth in one of our patients.

Growth hormone is permissive for neoplastic colon growth

Growth hormone (GH) excess in acromegaly is associated with increased precancerous colon polyps and soft tissue adenomas, whereas short-stature humans harboring an inactivating GH receptor mutation do not develop cancer. We show that locally expressed colon GH is abundant in conditions predisposing to colon cancer and in colon adenocarcinoma-associated stromal fibroblasts. Administration of a GH receptor (GHR) blocker in acromegaly patients induced colon p53 and adenomatous polyposis coli (APC), reversing progrowth GH signals. p53 was also induced in skin fibroblasts derived from short-statured humans with mutant GHR. GH-deficient prophet of pituitary-specific positive transcription factor 1 (Prop1)(-/-) mice exhibited induced colon p53 levels, and cross-breeding them with Apc(min+/-) mice that normally develop intestinal and colon tumors resulted in GH-deficient double mutants with markedly decreased tumor number and size. We also demonstrate that GH suppresses p53 and reduces apoptosis in human colon cell lines as well as in induced human pluripotent stem cell-derived intestinal organoids, and confirm in vivo that GH suppresses colon mucosal p53/p21. GH excess leads to decreased colon cell phosphatase and tensin homolog deleted on chromosome 10 (PTEN), increased cell survival with down-regulated APC, nuclear β-catenin accumulation, and increased epithelial-mesenchymal transition factors and colon cell motility. We propose that GH is a molecular component of the "field change" milieu permissive for neoplastic colon growth.

361 GROWTH HORMONE RECEPTOR MUTANT PIGS PRODUCED BY USING THE CLUSTERED REGULARLY INTERSPACED SHORT PALINDROMIC REPEATS (CRISPR) AND CRISPR-ASSOCIATED SYSTEMS IN IN VITRO-PRODUCED ZYGOTES

Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas) technology is considered as an efficient strategy for generating gene edited large animals, such as pigs. Compared to somatic cell nuclear transfer, this new technology offers a relatively simple way to generate mutant pigs by direct injection of RNA into the cytoplasm of zygotes. Moreover, the use of in vitro produced zygotes would provide a highly effective and practical method for the production of porcine disease models for biomedical research. Here we examined the production efficiency of growth hormone receptor (GHR) mutant pigs by the combination of the CRISPR/Cas system and in vitro produced zygotes. In vitro maturation (IVM) of oocytes was performed as described previously (Kurome et al., Meth. Mol. Biol., in press). In all experiments, the same batch of frozen sperm was used. After IVM, around 20 oocytes with expanded cumulus cells were incubated with 5 × 104 spermatozoa in a 100-μL drop of porcine fertilization medium for 7 h. In vitro-produced embryos were assessed by the ratio of normal fertilization (eggs with 2 pronuclei) and blastocyst formation at Day 7. The Cas9 mRNA and a single guide RNA, recognising a short sequence of 20 base pairs in exon 3 of the GHR gene, were injected directly into the cytoplasm of the embryos 8.5 to 9.5 h after IVF. Injected embryos were transferred laparoscopically to recipient pigs, and 86.4% (57/66) of sperm-penetrated oocytes (66/96) exhibited normal fertilization. Incidence of polyspermy was relatively low (9/66, 13.6%). Developmental ability of in vitro-produced embryos to the blastocyst stage was 17.4% (24/138). In total, 426 RNA-injected embryos were transferred into 2 recipients, one of which became pregnant and gave birth to 8 piglets. All piglets were clinically healthy and developed normally. In 3 out of 8 piglets (37.5%), mutations were introduced. Next-generation sequencing revealed that all of them were mosaics: one with a single mutation (22% wild-type/78% mutant) and 2 piglets with 2 different mutations (80% wild-type/2% mutant_1/18% mutant_2 and 94% wild-type/4% mutant_1/2% mutant_2). Four out of 5 mutations caused a frameshift in the GHR gene. Our study reports for the first time generation of GHR mutant pigs by the use of the CRISPR/Cas system in in vitro-produced zygotes. Because all GHR mutant offspring were mosaic, Cas9 activation probably occurred after the 1-cell stage under our experimental conditions. The founder animal with the highest proportion of mutant GHR alleles will be used for breeding to establish a large animal model for Laron syndrome.This work is supported by the German Research Council (TR-CRC 127).