Genetic control of growth

Short Stature due to Bioinactive Growth Hormone (Kowarski Syndrome)

OBJECTIVE

Bioinactive growth hormone (BGH) is a structurally abnormal, biologically inactive, but immunoreactive form of growth hormone encoded by pathogenic growth hormone 1 gene variants. The underlying cause of the defective physiology is decreased BGH binding affinity to both growth hormone binding proteins and growth hormone receptors (GHRs). GHR cannot dimerize when it is in a quiescent state because BGH cannot activate it. Nondimerized GHR is unable to activate intracytoplasmic signaling pathway molecules such as Janus kinase 2 and signal transducer and activator of transcription, which initiate insulin-like growth factor-1 (IGF-1) transcription. IGF-1 cannot therefore be synthesized and IGF-1 levels in the circulation decrease. In contrast to children with growth hormone insensitivity, children with short stature due to BGH, known as Kowarski syndrome, exhibit an outstanding linear growth response to recombinant growth hormone therapy. For a number of reasons, differential diagnosis presents some difficulties. Similar diseases caused by genetic abnormalities that cause short stature range in severity from minor to severe clinical spectrum. Furthermore, some patients with Kowarski syndrome have previously been diagnosed with familial short stature, constitutional delayed puberty, and idiopathic short stature. This paper aims to review the particular clinical and laboratory findings of BGH.

METHODS

This study collected clinical and laboratory data from KS cases reported in the literature.

RESULTS

This review reports that KS cases have lower SDSs for height and IGF-1 compared to growth hormone deficiency.

CONCLUSION

The diversity of genetic defects underlying Kowarski syndrome (KS) will provide new insights into growth hormone insensitivity. As the availability of genetic analysis, including functional investigations expands, researchers will identify new underlying genetic pathways.

Management of Neonatal Isolated and Combined Growth Hormone Deficiency: Current Status

Congenital growth hormone deficiency (GHD) is a rare disease caused by disorders affecting the morphogenesis and function of the pituitary gland. It is sometimes found in isolation but is more frequently associated with multiple pituitary hormone deficiency. In some cases, GHD may have a genetic basis. The many clinical signs and symptoms include hypoglycaemia, neonatal cholestasis and micropenis. Diagnosis should be made by laboratory analyses of the growth hormone and other pituitary hormones, rather than by cranial imaging with magnetic resonance imaging. When diagnosis is confirmed, hormone replacement should be initiated. Early GH replacement therapy leads to more positive outcomes, including reduced hypoglycaemia, growth recovery, metabolic asset, and neurodevelopmental improvements.

Short stature related to Growth Hormone Insensitivity (GHI) in childhood

Linear growth during childhood is the result of the synergic contribution of different factors. The best growth determinant system during each period of life is represented by the growth hormone-insulin-like growth factor axis (GH-IGF), even if several other factors are involved in normal growth. Within the broad spectrum of growth disorders, an increased importance has been placed on growth hormone insensitivity (GHI). GHI was reported for the first time by Laron as a syndrome characterized by short stature due to GH receptor (GHR) mutation. To date, it is recognized that GHI represents a wide diagnostic category, including a broad spectrum of defects. The peculiar characteristic of GHI is the low IGF-1 levels associated with normal or elevated GH levels and the lack of IGF-1 response after GH administration. Recombinant IGF-1 preparations may be used in the treatment of these patients.

Genetic architecture and heritability of early-life telomere length in a wild passerine

Early-life telomere length (TL) is associated with fitness in a range of organisms. Little is known about the genetic basis of variation in TL in wild animal populations, but to understand the evolutionary and ecological significance of TL it is important to quantify the relative importance of genetic and environmental variation in TL. In this study, we measured TL in 2746 house sparrow nestlings sampled across 20 years and used an animal model to show that there is a small heritable component of early-life TL (h²  = 0.04). Variation in TL among individuals was mainly driven by environmental (annual) variance, but also brood and parental effects. Parent-offspring regressions showed a large maternal inheritance component in TL ( h maternal 2  = 0.44), but no paternal inheritance. We did not find evidence for a negative genetic correlation underlying the observed negative phenotypic correlation between TL and structural body size. Thus, TL may evolve independently of body size and the negative phenotypic correlation is likely to be caused by nongenetic environmental effects. We further used genome-wide association analysis to identify genomic regions associated with TL variation. We identified several putative genes underlying TL variation; these have been inferred to be involved in oxidative stress, cellular growth, skeletal development, cell differentiation and tumorigenesis in other species. Together, our results show that TL has a low heritability and is a polygenic trait strongly affected by environmental conditions in a free-living bird.

Novel Insights Into the Genetic Causes of Short Stature in Children

Short stature is a common reason for consulting a growth specialist during childhood. Normal height is a polygenic trait involving a complex interaction between hormonal, nutritional and psychosocial components. Genetic factors are becoming very important in the understanding of short stature. After exclusion of the most frequent causes of growth failure, clinicians need to evaluate whether a genetic cause might be taken into consideration. In fact, genetic causes of short stature are probably misdiagnosed during clinical practice and the underlying cause of short stature frequently remains unknown, thus classifying children as having idiopathic short stature (ISS). However, over the past decade, novel genetic techniques have led to the discovery of novel genes associated with linear growth and thus to the ability to define new possible aetiologies of short stature. In fact, thanks to the newer genetic advances, it is possible to properly re-classify about 25–40% of children previously diagnosed with ISS. The purpose of this article is to describe the main monogenic causes of short stature, which, thanks to advances in molecular genetics, are assuming an increasingly important role in the clinical approach to short children.

Potentialities of Gene Therapy in Pediatric Endocrinology

Gene therapy has become an appealing therapeutic option in many pediatric fields, including endocrinology. Unlike traditional drugs based on molecules that require repeated and frequent burdensome administrations, a single genetic therapeutic intervention may allow durable and curative clinical benefits. Although this highly innovative technology holds a great promise for the treatment of monogenic diseases, its clinical applications in the field of endocrinology have been so far challenging. In this review, we will discuss various ex vivo and in vivo approaches and potential applications of gene addition and gene editing approaches for treating hyperfunctional and hypofunctional endocrine diseases due to intrinsic defects or autoimmune origin. We will focus on the recent advances in gene therapy approaches aimed at treating type 1 diabetes and monogenic forms of endocrinopathies such as growth hormone deficiency, congenital adrenal hyperplasia, diabetes insipidus, IPEX, as well as their trends and future directions.

Polymorphism of the growth hormone gene GH1 in Polish children and adolescents with short stature

PURPOSE

Short stature in children is a significant medical problem which, without proper diagnosis and treatment, can lead to long-term consequences for physical and psychological health in adult life. Since human height is a polygenic and highly heritable trait, numerous variants in the genes involved in growth-including the growth hormone (GH1) gene-have been identified as causes of short stature.

METHODS

In this study, we performed for the first time molecular analysis of the GH1 gene in a cohort (n = 186) of Polish children and adolescents with short stature, suffering from growth hormone deficiency (GHD) or idiopathic short stature (ISS), and a control cohort (n = 178).

RESULTS

Thirteen SNP variants were identified, including four missense variants, six in 5'UTR, and three in introns. The frequency of minor missense variants was low (<0.02) and similar in the compared cohorts. However, two of these variants, Ala39Val (rs151263636) and Arg42Leu (rs371953554), were found (heterozygote status) in only two GHD patients. These substitutions, according to databases, can potentially be deleterious.

CONCLUSIONS

Mutations of GH1 causing short stature are very rare in the Polish population, but two potentially causative variants need further studies in a larger cohort of GHD patients.

Congenital Hypopituitarism During the Neonatal Period: Epidemiology, Pathogenesis, Therapeutic Options, and Outcome

Introduction: Congenital hypopituitarism (CH) is characterized by a deficiency of one or more pituitary hormones. The pituitary gland is a central regulator of growth, metabolism, and reproduction. The anterior pituitary produces and secretes growth hormone (GH), adrenocorticotropic hormone, thyroid-stimulating hormone, follicle-stimulating hormone, luteinizing hormone, and prolactin. The posterior pituitary hormone secretes antidiuretic hormone and oxytocin. Epidemiology: The incidence is 1 in 4,000-1 in 10,000. The majority of CH cases are sporadic; however, a small number of familial cases have been identified. In the latter, a molecular basis has frequently been identified. Between 80-90% of CH cases remain unsolved in terms of molecular genetics. Pathogenesis: Several transcription factors and signaling molecules are involved in the development of the pituitary gland. Mutations in any of these genes may result in CH including HESX1, PROP1, POU1F1, LHX3, LHX4, SOX2, SOX3, OTX2, PAX6, FGFR1, GLI2, and FGF8. Over the last 5 years, several novel genes have been identified in association with CH, but it is likely that many genes remain to be identified, as the majority of patients with CH do not have an identified mutation. Clinical manifestations: Genotype-phenotype correlations are difficult to establish. There is a high phenotypic variability associated with different genetic mutations. The clinical spectrum includes severe midline developmental disorders, hypopituitarism (in isolation or combined with other congenital abnormalities), and isolated hormone deficiencies. Diagnosis and treatment: Key investigations include MRI and baseline and dynamic pituitary function tests. However, dynamic tests of GH secretion cannot be performed in the neonatal period, and a diagnosis of GH deficiency may be based on auxology, MRI findings, and low growth factor concentrations. Once a hormone deficit is confirmed, hormone replacement should be started. If onset is acute with hypoglycaemia, cortisol deficiency should be excluded, and if identified this should be rapidly treated, as should TSH deficiency. This review aims to give an overview of CH including management of this complex condition.

Comparative transcriptomics identifies genes differentially expressed in the intestine of a new fast-growing strain of common carp with higher unsaturated fatty acid content in muscle

We have created a new, fast-growing strain of common carp with higher unsaturated fatty acid content in muscle. To better understand the impacts of gene regulation in intestinal tissue on growth and unsaturated fatty acid content, we conducted a comparative RNA-Seq transcriptome analysis between intestine samples of Selected and Control groups (and corroborated selected results by PCR). After eight weeks of cage culture, weight gain of the Selected group was 20.84% higher. In muscles of the control group, monounsaturated fatty acids (FAs) were more abundant, whereas polyunsaturated FAs were more abundant in muscles of the Selected group. In total, we found 106 differentially expressed genes (DEGs) between the two groups. Only the endocytosis pathway was significantly enriched in DEGs, with two upregulated genes: il2rb and ehd1. The latter is involved in the growth hormone/insulin-like growth factor (Gh/Igf) axis, which plays a key role in the regulation of growth in animals. tll2, which is known to be associated with intestinal regeneration, was extremely highly upregulated in both transcriptomic (infinite) and qPCR (610.70) analyses. Two of the upregulated genes are associated with the fatty acid metabolism, several genes are likely to be indicators of heightened transcription levels, several are associated with metabolic and developmental roles, several with neuronal functions (including two with vision), several with the immune system, and two downregulated genes with the development of vasculature. The higher growth rate of the Selected group is likely to be at least partially attributed to increased endocytosis efficiency and genetically-driven behavioural differences (higher aggression levels). There are some indications that this new strain might have slightly impaired immune responses, and a higher propensity for inherited diseases leading to sight impairment, as well for neurodegenerative diseases in general, but these indications still need to be confirmed.

Growth Hormone Deficiency in Children: From Suspecting to Diagnosing

Isolated Growth hormone deficiency is an important and treatable cause of short stature. However, it is often difficult to diagnose the condition with certainty due to the lack of a single robust diagnostic test. Short children, other than those with the classical phenotype of immature chubby facies, truncal obesity and micropenis in boys, or those with history of cranial lesions with known association with hypopituitarism, should be evaluated for growth hormone deficiency only after excluding the other more common conditions. These children typically have height markedly below that expected for their midparental height with low height velocity and delayed bone age. Growth hormone levels should be checked by provocative testing, after ensuring that the child is euthyroid, and after priming with sex steroids if indicated. Low levels of Insulin-like growth factor 1 and Insulin-like growth factor binding protein 3 and pituitary abnormalities on neuroimaging provide important corroborative evidence to the diagnosis.

Long-Term Outcomes, Genetics, and Pituitary Morphology in Patients with Isolated Growth Hormone Deficiency and Multiple Pituitary Hormone Deficiencies: A Single-Centre Experience of Four Decades of Growth Hormone Replacement

BACKGROUND

Growth hormone (GH) has been used to treat children with GH deficiency (GHD) since 1966.

AIMS

Using a combined retrospective and cross-sectional approach, we explored the long-term outcomes of patients with GHD, analysed factors influencing therapeutic response, determined persistence into adulthood, investigated pituitary morphology, and screened for mutations in causative genes.

METHODS

The files of 96 GH-deficient children were reviewed. In a subset of 50 patients, re-assessment in adulthood was performed, including GHRH-arginine testing, pituitary magnetic resonance imaging (MRI), and mutational screening for the growth hormone-1 gene (GH1) and the GHRH receptor gene (GHRHR) in isolated GHD (IGHD), and HESX1, PROP1, POU1F1, LHX3, LHX4, and GLI2 in multiple pituitary hormone deficiency (MPHD) patients.

RESULTS

GH was started at a height SDS of -3.2 ± 1.4 in IGHD patients and of -4.1 ± 2.1 in MPHD patients. Relative height gain was 0.3 SDS/year, absolute gain 1.6 SDS, and 1.2/2.6 SDS in IGHD/MPHD, respectively. Mid-parental target height was reached in 77%. Initial height SDS, bone age retardation and duration of GH replacement were correlated with height SDS gain. GHD persisted into adulthood in 19 and 89% of subjects with IGHD and MPHD, respectively. In 1/42 IGHD patients a GH1 mutation was detected; PROP1 mutations were found in 3/7 MPHD subjects. Anterior pituitary hypoplasia, combined with posterior pituitary ectopy and pituitary stalk invisibility on MRI, was an exclusive finding in MPHD patients.

CONCLUSIONS

GH replacement successfully corrects the growth deficit in children with GHD. While the genetic aetiology remains undefined in most cases of IGHD, PROP1 mutations constitute a major cause for MPHD. Persistence of GHD into adulthood is related to abnormal pituitary morphology.

Targeting GH-1 splicing as a novel pharmacological strategy for growth hormone deficiency type II

Isolated growth hormone deficiency type II (IGHD II) is a rare genetic splicing disorder characterized by reduced growth hormone (GH) secretion and short stature. It is mainly caused by autosomal dominant-negative mutations within the growth hormone gene (GH-1) which results in missplicing at the mRNA level and the subsequent loss of exon 3, producing the 17.5-kDa GH isoform: a mutant and inactive GH protein that reduces the stability and the secretion of the 22-kDa GH isoform, the main biologically active GH form. At present, patients suffering from IGHD II are treated with daily injections of recombinant human GH (rhGH) in order to reach normal height. However, this type of replacement therapy, although effective in terms of growth, does not prevent the toxic effects of the 17.5-kDa mutant on the pituitary gland, which may eventually lead to other hormonal deficiencies. As the severity of the disease inversely correlates with the 17.5-kDa/22-kDa ratio, increasing the inclusion of exon 3 is expected to ameliorate disease symptoms. This review focuses on the recent advances in experimental and therapeutic strategies applicable to treat IGHD II in clinical and preclinical contexts. Several avenues for alternative IGHD II therapy will be discussed including the use of small interfering RNA (siRNA) and short hairpin RNA (shRNA) constructs that specifically target the exon 3-deleted transcripts as well as the application of histone deacetylase inhibitors (HDACi) and antisense oligonucleotides (AONs) to enhance full-length GH-1 transcription, correct GH-1 exon 3 splicing and manipulate GH pathway.

GPR101 Mutations are not a Frequent Cause of Congenital Isolated Growth Hormone Deficiency

Patients with Xq26.3 microduplication present with X-linked acrogigantism (X-LAG) syndrome, an early-childhood form of gigantism due to marked growth hormone (GH) hypersecretion from mixed GH-PRL adenomas and hyperplasia. The microduplication includes GPR101, which is upregulated in patients' tumor tissue. The GPR101 gene codes for an orphan G protein coupled receptor that is normally highly expressed in the hypothalamus. Our aim was to determine whether GPR101 loss of function mutations or deletions could be involved in patients with congenital isolated GH deficiency (GHD). Taking advantage of the cohort of patients from the GENHYPOPIT network, we studied 41 patients with unexplained isolated GHD. All patients had Sanger sequencing of the GPR101 gene and array comparative genome hybridization (aCGH) to look for deletions. Functional studies (cell culture with GH secretion measurements, cAMP response) were performed. One novel GPR101 variant, c.589 G>T (p.V197L), was seen in the heterozygous state in a patient with isolated GHD. In silico analysis suggested that this variant could be deleterious. Functional studies did not show any significant difference in comparison with wild type for GH secretion and cAMP response. No truncating, frameshift, or small insertion-deletion (indel) GPR101 mutations were seen in the 41 patients. No deletion or other copy number variation at chromosome Xq26.3 was found on aCGH. We found a novel GPR101 variant of unknown significance, in a patient with isolated GH deficiency. Our study did not identify GPR101 abnormalities as a frequent cause of GH deficiency.

IGHD II: A Novel GH-1 Gene Mutation (GH-L76P) Severely Affects GH Folding, Stability, and Secretion

CONTEXT

The autosomal dominant form of GH deficiency (IGHD II) is characterized by markedly reduced GH secretion combined with low concentrations of IGF-1 leading to short stature.

OBJECTIVE

Structure-function analysis of a missense mutation in the GH-1 gene converting codon 76 from leucine (L) to proline (P) yielding a mutant GH-L76P peptide.

DESIGN, SETTINGS, AND PATIENTS

Heterozygosity for GH-L76P/wt-GH was identified in a nonconsanguineous Spanish family. The index patients, two siblings, a boy and a girl, were referred for assessment of their short stature (-3.2 and -3.8 SD). Their grandmother, father, and aunt were also carrying the same mutation and showed severe short stature; therefore, IGHD II was diagnosed.

INTERVENTIONS AND RESULTS

AtT-20 cells coexpressing both wt-GH and GH-L76P showed a reduced GH secretion (P < .001) after forskolin stimulation when compared with the cells expressing only wt-GH. In silico mutagenesis and molecular dynamics simulations presented alterations of correct folding and mutant stability compared with wt-GH. Therefore, further structural analysis of the GH-L76P mutant was performed using expressed and purified proteins in Escherichia coli by thermofluor assay and fast degradation proteolysis assay. Both assays revealed that the GH-L76P mutant is unstable and misfolded compared to wt-GH confirming the bioinformatic model prediction.

CONCLUSIONS

This is the first report of a family suffering from short stature caused by IGHD II, which severely affects intracellular GH folding and stability as well as secretion, highlighting the necessity of functional analysis of any GH variant for defining new mechanisms as a cause for IGHD II.

A novel gross indel in the growth hormone releasing hormone receptor gene of Indian IGHD patients

CONTEXT

Cohort specific mutations in the growth hormone (GH1) and growth hormone-releasing hormone receptor (GHRHR) genes have been reported worldwide in isolated growth hormone deficiency (IGHD) patients. However, limited data is available on ethnically diverse Indian IGHD patients.

OBJECTIVE

The aim of the study was to find GH1 and GHRHR gene mutations in Indian IGHD patients from two unrelated non-consanguineous families.

DESIGN

The 5' and 3' untranslated regions (UTRs) and coding regions with splice sites of the GH1 and GHRHR genes were sequenced for all patients (n=6). Family members and 20 controls were evaluated for the sequence variants identified in the index patients. Online bioinformatics tools were used to confirm mutations and their pathogenicity.

RESULTS

GHRHR gene mutations were observed in all patients. Interestingly, a novel indel g.30999250_31006943delinsAGAGATCCA was observed in both the unrelated families. Three patients were homozygous for the novel indel, two were homozygous for the previously reported p.E72X mutation and one was compound heterozygous with both the mutations (indel and p.E72X) in the GHRHR gene. The novel indel has resulted in the loss of 5' regulatory region and exon 1 of the GHRHR gene impairing the GHRHR expression. All the normal family members were heterozygous either for the indel or p.E72X mutation. None of the patients had GH1 gene mutations.

CONCLUSIONS

We describe a novel gross indel in the GHRHR gene resulting in the loss of 5' regulatory region and GHRHR exon 1 in four IGHD IB patients from two unrelated non-consanguineous Indian families.

Genetic evaluation of short stature

CONTEXT

Genetics plays a major role in determining an individual's height. Although there are many monogenic disorders that lead to perturbations in growth and result in short stature, there is still no consensus as to the role that genetic diagnostics should play in the evaluation of a child with short stature.

EVIDENCE ACQUISITION

A search of PubMed was performed, focusing on the genetic diagnosis of short stature as well as on specific diagnostic subgroups included in this article. Consensus guidelines were reviewed.

EVIDENCE SYNTHESIS

There are a multitude of rare genetic causes of severe short stature. There is no high-quality evidence to define the optimal approach to the genetic evaluation of short stature. We review genetic etiologies of a number of diagnostic subgroups and propose an algorithm for genetic testing based on these subgroups.

CONCLUSION

Advances in genomic technologies are revolutionizing the diagnostic approach to short stature. Endocrinologists must become facile with the use of genetic testing in order to identify the various monogenic disorders that present with short stature.

Height matters-from monogenic disorders to normal variation

Height is a classic polygenic quantitative trait with a high level of heritability. As it is a simple and stable parameter to measure, height is a model for both common, complex disorders and monogenic, Mendelian disease. In this Review, we examine height from the perspective of monogenic and complex genetics and discuss the lessons learned so far. We explore several examples of rare sequence variants with large effects on height and compare these variants to the common variants identified in genome-wide association studies that have small effects on height. We discuss how copy number changes or genetic interactions might contribute to the unidentified aspects of the heritability of height. We also ask whether information derived from genome-wide association studies on specific loci in the vicinity of genes can be used for further research in clinical paediatric endocrinology. Furthermore, we address key challenges that remain for gene discovery and for the transition of moving from genomic localization to mechanistic insights, with an emphasis on using next-generation sequencing to identify causative variants of people at the extremes of height distribution.

Insulin-like growth factor I: could it be a marker of prematurity in the foal?

Insulin-like growth factor (IGF)-I represents one of the most important growth regulators, playing a central role in fetal and neonatal growth. Plasma IGF-I levels increase rapidly after birth, and they are influenced by numerous factors, including sex, age, nutritional state, and premature birth. The aims of this study were: (1) to evaluate the IGF-I plasma profile in healthy newborn foals during the first 2 weeks of life; (2) to assess the possible influence of sex and birth weight on this hormone; (3) to analyze the percentage increment of IGF-I values in healthy foals; (4) to evaluate the influence of prematurity on IGF-I profile; (5) to verify the role of IGF-I as a diagnostic marker of prematurity; and (6) to analyze the percentage increment of IGF-I in premature foals. Thirty-four healthy term foals were enrolled as the control group and from each foal plasma was collected within 6 hours from birth, at 12 hours, daily from Day 1 to Day 7, and at Days 10 and 14 after birth. Eleven foals aged younger than 1 week and diagnosed as premature and hospitalized at a Equine Perinatology Unit were also enrolled; from each foal plasma was collected daily from the day of admission to discharge or death. Insulin-like growth factor I was analyzed by RIA. In the control group, an increasing trend of IGF-I concentrations was found, with higher values from Day 4 to 10 compared with data obtained at less than 6 hours of life, and from Day 5 to 10 compared with 12 and 24 hours and 3 days. No differences were found in healthy foals analyzed in relation to birth weight and sex. In premature foals an increasing trend was observed but no statistical differences were found among sampling times, and no differences were found between healthy and premature foals. The IGF value in premature foals at admission was always higher compared with the lowest recorded level in healthy age-matched foals, thus this parameter does not seem to have a diagnostic role for prematurity in foals. Finally, the evaluation of the percentage increment of IGF-I concentrations showed a significant increase in full-term foals on Day 5, 6, 7, and 10 compared with 12 and 24 hours, and no differences were observed in premature foals. In conclusion, prematurity in newborn foals seems to affect only partially IGF-I plasma concentrations and it does not seem to be a reliable marker for this pathological condition.

Type IA isolated growth hormone deficiency (IGHD) consistent with compound heterozygous deletions of 6.7 and 7.6 Kb at the GH1 gene locus

Isolated growth hormone deficiency (IGHD) may result from deletions/mutations in either GH1 or GHRHR genes. The objective of this study was to characterize the molecular defect in a girl presenting IGHD. The patient was born at 41 weeks of gestation from non-consanguineous parents. Clinical and biochemical evaluation included anthropometric measurements, evaluation of pituitary function, IGF-I and IGFBP-3 levels. Molecular characterization was performed by PCR amplification of GH1 gene and SmaI digestion of two homologous fragments flanking the gene, using genomic DNA from the patient and her parents as templates. At 1.8 years of age the patient presented severe growth retardation (height 61.2 cm, -7.4 SDS), truncal obesity, frontal bossing, doll face, and acromicria. MRI showed pituitary hypoplasia. Laboratory findings confirmed IGHD. GH1 gene could not be amplified in samples from the patient while her parents yielded one fragment of the expected size. SmaI digestion was consistent with the patient being compound heterozygous for 6.7 and 7.6 Kb deletions, while her parents appear to be heterozygous carriers for either the 6.7 or the 7.6 Kb deletions. We have characterized type IA IGHD caused by two different GH1 gene deletions, suggesting that this condition should be considered in severe IGHD, even in non-consanguineous families. Arq Bras Endocrinol Metab. 2012;56(8):558-63

Stimulation of mechano-growth factor expression by myofibrillar proteins in murine myoblasts and myotubes

Mechano-growth factor (MGF) is a product of alternative splicing of the insulin-like growth factor 1 (IGF-1) mRNA. MGF is known to stimulate myoblast proliferation and to protect neurons and cardiomyocytes from apoptosis. MGF expression is dramatically increased in response to mechanical stimuli and tissue damage. The mechanisms of induction of MGF expression are as yet imperfectly understood. There is certain evidence that some protein factors able to stimulate MGF synthesis in normal myoblasts are released from damaged muscle. This study was undertaken to explore the nature of these protein inductors of MGF expression and to investigate the mechanism of their action. We report here that myofibrillar fraction of skeletal muscle homogenate activated MGF expression in murine myoblasts and myotubes in culture. The expression of another splice form of IGF-1 gene, IGF-1Ea, was also stimulated by myofibrils. Three myofibrillar proteins able to stimulate MGF synthesis were isolated. These proteins were identified by MALDI and immunoblotting as myomesin, myosin-binding protein C, and titin. The activation of MGF expression was associated with the increase of cAMP level in the cells. Inhibitor of adenylyl cyclase dideoxyadenosine arrested stimulation of MGF synthesis by all three myofibrillar proteins.

Genomics in pediatric endocrinology-genetic disorders and new techniques

In the last few years, there have been remarkable advances in the development of new and more sophisticated genetic techniques. These have allowed a better understanding of the molecular mechanisms of genetically determined pediatric endocrine disorders and are paving the way for a radical change in diagnosis and treatment. This article introduces some of these concepts and some of the genetic techniques being used.

A novel GH-1 gene mutation (GH-P59L) causes partial GH deficiency type II combined with bioinactive GH syndrome

CONTEXT AND OBJECTIVE

Despite the differences in the main characteristics between the autosomal dominant form of GH deficiency (IGHD II) and the bioinactive GH syndrome, a common feature of both is their impact on linear growth leading to short stature in all affected patients.

DESIGN

The index patient, a boy, was referred for assessment of his short stature (-2.54 SD score) and a delayed bone age of 5.9 yrs at the chronological age of 7.7 yrs. The GHD was confirmed by standard GH provocation tests, which revealed modestly reduced GH and IGF-I concentrations. Further genetic analysis of GH-1 gene identified heterozygosity for GH-P59L mutation. The secretion of the GH-P59L following stimulation with forskolin was investigated and compared to that of the wt-GH after expression of both GH variants in AtT-20 cells. Based on the position of P59L mutation that lies within a patch of residues composing the GH binding site 1 for GHR, we performed the analysis of GH-P59L binding to GHR by in silico mutagenesis and molecular dynamics simulations, which suggested possible problems in correct binding of GH-P59L to the GHR. Therefore, the functional characterization of this GH mutant was assessed through studies of GHR binding and activation of Jak2/Stat5 signaling pathway.

RESULTS

In line with the clinical data of the patient GH deficiency is suggested, underlined by GH-secretion studies revealing a moderate difference in secretion between GH-P59L and wt-GH. In addition, further functional characterization of the GH-P59L by studies of GH-receptor binding and activation of Jak2/Stat5 pathway presented with a reduced binding affinity of GH-P59L for GHR and decreased bioactivity compared to the wt-GH.

CONCLUSIONS

The clinical data of the patient combined with the laboratory data support the diagnosis of partial IGHD type II. Since the GH deficiency was not total, additional binding and signaling studies were performed, which revealed that the GH-P59L variant displays some of the common features of bioinactive GH syndrome. Taken together, in this study we report a patient suffering from the combination of two growth disorders (alteration of secretion as well as bioactivity) caused by a GH-1 gene alteration highlighting the necessity of functional analysis of any GH variant, despite the presence of obvious clinical features of IGHD type II.

Genetics of GHRH, GHRH-receptor, GH and GH-receptor: its impact on pharmacogenetics

When a child is not following the normal, predicted growth curve, an evaluation for underlying illnesses and central nervous system abnormalities is required and, appropriate consideration should be given to genetic defects causing GH deficiency (GHD). Because Insulin-like-Growth Factor-I (IGF-I) plays a pivotal role, GHD could also be considered as a form of IGF-I deficiency (IGFD). Although IGFD can develop at any level of the GHRH-GH-IGF axis, a differentiation should be made between GHD (absent to low GH in circulation) and IGFD (normal to high GH in circulation). The main focus of this review is on the GH-gene, the various gene alterations and their possible impact on the pituitary gland. However, although transcription factors regulating the pituitary gland development may cause multiple pituitary hormone deficiency they may present initially as GHD. These defects are discussed in various different chapters within this book, whereas, the impact of alterations of the GHRH-, GHRH-receptor- --as well as the GH-receptor (GHR) gene--will be discussed here.

Genetic evaluation of short stature

After a proper medical history, growth analysis and physical examination of a short child, followed by radiological and laboratory screening, the clinician may decide to perform genetic testing. We propose several clinical algorithms that can be used to establish the diagnosis. GH1 and GHRHR should be tested in children with severe isolated growth hormone deficiency and a positive family history. A multiple pituitary dysfunction can be caused by defects in several genes, of which PROP1 and POU1F1 are most common. GH resistance can be caused by genetic defects in GHR, STAT5B, IGF1, IGFALS, which all have their specific clinical and biochemical characteristics. IGF-I resistance is seen in heterozygous defects of the IGF1R. If besides short stature additional abnormalities are present, these should be matched with known dysmorphic syndromes. If no obvious candidate gene can be determined, a whole genome approach can be taken to check for deletions, duplications and/or uniparental disomies.

Genetic defects causing functional and structural isolated growth hormone deficiency

Normal somatic growth requires the integrated function of many of the hormonal, metabolic, and other growth factors involved in the hypothalamo-pituitary-somatotrope axis. Human growth hormone (hGH) causes a variety of physiological and metabolic effects in humans and its pivotal role in postnatal growth is undisputed. Disturbances that occur during this process often cause subnormal GH secretion and/or subnormal GH sensitivity/responsiveness resulting in short stature. Despite the complexity of this linear growth process, the growth pattern of children, if evaluated in the context of normal standards, is rather predictable. Children presenting with short stature (i.e out of normal standards) are treated with daily injections of recombinant human GH (rhGH), which leads in almost all cases to an increase of height velocity. Although it is becoming more and more evident that many genes are involved in controlling the regulation of growth, the main aim of this review is to focus on the GH-1 gene, the various gene alterations and their important physiological and pathophysiological role in growth.

The fat mass and obesity associated gene FTO functions in the brain to regulate postnatal growth in mice

FTO (fat mass and obesity associated) was identified as an obesity-susceptibility gene by several independent large-scale genome association studies. A cluster of SNPs (single nucleotide polymorphism) located in the first intron of FTO was found to be significantly associated with obesity-related traits, such as body mass index, hip circumference, and body weight. FTO encodes a protein with a novel C-terminal α-helical domain and an N-terminal double-strand β-helix domain which is conserved in Fe(II) and 2-oxoglutarate-dependent oxygenase family. In vitro, FTO protein can demethylate single-stranded DNA or RNA with a preference for 3-methylthymine or 3-methyluracil. Its physiological substrates and function, however, remain to be defined. Here we report the generation and analysis of mice carrying a conditional deletion allele of Fto. Our results demonstrate that Fto plays an essential role in postnatal growth. The mice lacking Fto completely display immediate postnatal growth retardation with shorter body length, lower body weight, and lower bone mineral density than control mice, but their body compositions are relatively normal. Consistent with the growth retardation, the Fto mutant mice have reduced serum levels of IGF-1. Moreover, despite the ubiquitous expression of Fto, its specific deletion in the nervous system results in similar phenotypes as the whole body deletion, indicating that Fto functions in the central nerve system to regulate postnatal growth.

Genetic causes and treatment of isolated growth hormone deficiency-an update

Isolated growth hormone deficiency is the most common pituitary hormone deficiency and can result from congenital or acquired causes, although the majority of cases are idiopathic with no identifiable etiology. Known genes involved in the genetic etiology of isolated growth hormone deficiency include those that encode growth hormone (GH1), growth-hormone-releasing hormone receptor (GHRHR) and transcription factor SOX3. However, mutations are identified in a relatively small percentage of patients, which suggests that other, yet unidentified, genetic factors are involved. Among the known factors, heterozygous mutations in GH1 remain the most frequent cause of isolated growth hormone deficiency. The identification of mutations has clinical implications for the management of patients with this condition, as individuals with heterozygous GH1 mutations vary in phenotype and can, in some cases, develop additional pituitary hormone deficiencies. Lifelong follow-up of these patients is, therefore, recommended. Further studies in the genetic etiology of isolated growth hormone deficiency will help to elucidate mechanisms implicated in the control of growth and may influence future treatment options. Advances in pharmacogenomics will also optimize the treatment of isolated growth hormone deficiency and other conditions associated with short stature, for which recombinant human growth hormone is a licensed therapy.

Isolated GH deficiency type II: knockdown of the harmful Delta3GH recovers wt-GH secretion in rat tumor pituitary cells

Isolated GH deficiency type II (IGHD II) is the autosomal dominant form of GHD. In the majority of the cases, this disorder is due to specific GH-1 gene mutations that lead to mRNA missplicing and subsequent loss of exon 3 sequences. When misspliced RNA is translated, it produces a toxic 17.5-kDa GH (Delta3GH) isoform that reduces the accumulation and secretion of wild-type-GH. At present, patients suffering from this type of disease are treated with daily injections of recombinant human GH in order to maintain normal growth. However, this type of replacement therapy does not prevent toxic effects of the Delta3GH mutant on the pituitary gland, which can eventually lead to other hormonal deficiencies. We developed a strategy involving Delta3GH isoform knockdown mediated by expression of a microRNA-30-adapted short hairpin RNA (shRNA) specifically targeting the Delta3GH mRNA of human (shRNAmir-Delta3). Rat pituitary tumor GC cells expressing Delta3GH upon doxycycline induction were transduced with shRNAmir-Delta3 lentiviral vectors, which significantly reduced Delta3GH protein levels and improved human wild-type-GH secretion in comparison with a shRNAmir targeting a scrambled sequence. No toxicity due to shRNAmir expression could be observed in cell proliferation assays. Confocal microscopy strongly suggested that shRNAmir-Delta3 enabled the recovery of GH granule storage and secretory capacity. These viral vectors have shown their ability to stably integrate, express shRNAmir, and rescue IGHD II phenotype in rat pituitary tumor GC cells, a methodology that opens new perspectives for the development of gene therapy to treat IGHD patients.

Genetics of isolated growth hormone deficiency

When a child is not following the normal, predicted growth curve, an evaluation for underlying illnesses and central nervous system abnormalities is required, and appropriate consideration should be given to genetic defects causing growth hormone (GH) deficiency (GHD). Because Insulin-like Growth Factor-I (IGF-I) plays a pivotal role, GHD could also be considered as a form of IGF-I deficiency (IGFD). Although IGFD can develop at any level of the GH-releasing hormone (GHRH)-GH-IGF axis, a differentiation should be made between GHD (absent to low GH in circulation) and IGFD (normal to high GH in circulation). The main focus of this review is on the GH gene, the various gene alterations and their possible impact on the pituitary gland. However, although transcription factors regulating the pituitary gland development may cause multiple pituitary hormone deficiency, they may present initially as GHD.

Growth hormone (GH) deficiency type II: a novel GH-1 gene mutation (GH-R178H) affecting secretion and action

CONTEXT AND OBJECTIVE

Main features of the autosomal dominant form of GH deficiency (IGHD II) include markedly reduced secretion of GH combined with low concentrations of IGF-I leading to short stature.

DESIGN, SETTING, AND PATIENTS

A female patient presented with short stature (height -6.0 sd score) and a delayed bone age of 2 yr at the chronological age of 5 yr. Later, at the age of 9 yr, GHD was confirmed by standard GH provocation test, which revealed subnormal concentrations of GH and a very low IGF-I. Genetic analysis of the GH-1 gene revealed the presence of a heterozygous R178H mutation.

INTERVENTIONS AND RESULTS

AtT-20 cells coexpressing both wt-GH and GH-R178H showed a reduced GH secretion after forskolin stimulation compared with the cells expressing only wt-GH, supporting the diagnosis of IGHD II. Because reduced GH concentrations found in the circulation of our untreated patient could not totally explain her severe short stature, functional characterization of the GH-R178H performed by studies of GH receptor binding and activation of the Janus kinase-2/signal transducer and activator of transcription-5 pathway revealed a reduced binding affinity of GH-R178H for GH receptor and signaling compared with the wt-GH.

CONCLUSION

This is the first report of a patient suffering from short stature caused by a GH-1 gene alteration affecting not only GH secretion (IGHD II) but also GH binding and signaling, highlighting the necessity of functional analysis of any GH variant, even in the alleged situation of IGHD II.

Effect of genetic adjuvants on immune respondance, growth and hormone levels in somatostatin DNA vaccination-induced Hu lambs

The aim of current study was to evaluate the prospects of adjuvants against DNA vaccination (pES/2SS) encoding somatostatin (SS) and hepatitis B surface antigen fusion gene. A total of 60 female Hu lambs were divided into 6 groups and vaccinated in the context of various adjuvants (and controls): pE-CpG, Escherichia coli DH5alpha DNA, crude liposomes or GM-CSF in combination with the pES/2SS plasmid. Controls included pES/2SS only vaccinated and physiological saline groups. The antibody against SS level in the E. coli DH5alpha DNA group was significantly increased compared to that in the pES/2SS vaccine alone. Vaccination with pES/2SS/pE-CpG or pES/2SS/E. coli DH5alpha resulted in elevated weight gains that were 33.0 and 31.6% higher, respectively, than in saline group and pES/2SS only vaccinated controls. The concentrations of GH and IGF-I in the DNA vaccine groups were remarkably higher than those in the saline group, and those with positive antibody higher than negative antibody. These results suggested that different adjuvant/pES/2SS combinations can enhance the immune effect and had significant positive effects on growth.

The recognition and treatment of growth disorders - a 50-year retrospective

The past 50 years have seen great progress in the understanding and treatment of classic growth disorders. Advances such as the recognition of hormone receptor defects, the development of recombinant growth hormone, and the expanding awareness of epigenetic phenomena affecting growth are among these great achievements. Yet growth failure remains a pervasive problem among children with complex health conditions, such as survivors of childhood cancers, premature infants, organ transplant recipients, and children with cystic fibrosis. The significant increases in life expectancy among these groups underscores the potential consequences of poor growth, whether due to the underlying conditions or medical treatments, as they may have long-lasting effects into adulthood. The ongoing contributions of human biologists to the study of human growth remain essential in the recognition and treatment of growth disorders, by defining normal patterns of growth and body composition, the interplay of growth and maturation, the role of environmental, behavioral and genetic factors, and the long-term consequences of growth patterns. Examples will be given based on two common genetic disorders, cystic fibrosis and sickle-cell anemia, to highlight the relationships between growth failure, survival, and malnutrition. Also, a study of bone mineral accretion in children with cystic fibrosis will illustrate the importance of understanding patterns of growth in healthy children, and their application in the diagnosis and management of children with chronic disease. These examples accentuate the need for continued participation of human biologists in the study of growth and development and the care of children.

Genetic forms of hypopituitarism and their manifestation in the neonatal period

The anterior pituitary gland is a central regulator of growth, reproduction and homeostasis. The development of the pituitary gland depends on the sequential temporal and spatial expression of transcription factors and signalling molecules. Naturally occurring and transgenic murine models have demonstrated a role for many of these molecules in the aetiology of congenital hypopituitarism. These include the transcription factors HESX1, PROP1, POU1F1, LHX3, LHX4, PITX1, PITX2, OTX2, SOX2 and SOX3. Mutations in any of the genes involved in pituitary development may result in congenital hypopituitarism, which manifests as the deficiency in one or more pituitary hormones. The phenotype can be highly variable and may consist of isolated hypopituitarism, or more complex disorders such as septo-optic dysplasia (SOD) and holoprosencephaly. Neonates with congenital hypopituitarism may present with non-specific symptoms, with or without associated developmental defects such as ocular, midline and genital abnormalities. Alternatively, they may be initially asymptomatic but at risk of developing pituitary hormone deficiencies over time. The overall incidence of mutations in known transcription factors in patients with hypopituitarism is low, indicating that many genes remain to be identified. Their characterization will further elucidate the pathogenesis of this complex condition and will shed light on normal pituitary development.

Expanding the spectrum of mutations in GH1 and GHRHR: genetic screening in a large cohort of patients with congenital isolated growth hormone deficiency

CONTEXT

It is estimated that 3-30% of cases with isolated GH deficiency (IGHD) have a genetic etiology, with a number of mutations being reported in GH1 and GHRHR. The aim of our study was to genetically characterize a cohort of patients with congenital IGHD and analyze their characteristics.

PATIENTS AND METHODS

A total of 224 patients (190 pedigrees) with IGHD and a eutopic posterior pituitary were screened for mutations in GH1 and GHRHR. To explore the possibility of an association of GH1 abnormalities with multiple pituitary hormone deficiencies, we have screened 62 patients with either multiple pituitary hormone deficiencies (42 pedigrees), or IGHD with an ectopic posterior pituitary (21 pedigrees).

RESULTS

Mutations in GH1 and GHRHR were identified in 41 patients from 21 pedigrees (11.1%), with a higher prevalence in familial cases (38.6%). These included previously described and novel mutations in GH1 (C182X, G120V, R178H, IVS3+4nt, a>t) and GHRHR (W273S, R94L, R162W). Autosomal dominant, type II IGHD was the commonest form (52.4%), followed by type IB (42.8%) and type IA (4.8%). Patients with type II IGHD had highly variable phenotypes. There was no difference in the endocrinology or magnetic resonance imaging appearance between patients with and without mutations, although those with mutations presented with more significant growth failure (height, -4.7 +/- 1.6 SDS vs. -3.4 +/- 1.7 SDS) (P = 0.001). There was no apparent difference between patients with mutations in GH1 and GHRHR.

CONCLUSIONS

IGHD patients with severe growth failure and a positive family history should be screened for genetic mutations; the evolving endocrinopathy observed in some of these patients suggests the need for long-term follow-up.

Genomics in pediatric endocrinology--genetic disorders and new techniques

In the last few years, there have been remarkable advances in the development of new and more sophisticated genetic techniques. These have allowed a better understanding of the molecular mechanisms of genetically determined pediatric endocrine disorders and are paving the way for a radical change in diagnosis and treatment. This article introduces some of these concepts and some of the genetic techniques being used.

A fractionation method to identify qauntitative changes in protein expression mediated by IGF-1 on the proteome of murine C2C12 myoblasts

Although much is known about signal transduction downstream of insulin-like growth factor-1 (IGF-1), relatively little is known about the global changes in protein expression induced by this hormone. In this study, the acute effects of IGF-1 on the proteome of murine C2C12 cells were examined. Cells were treated with IGF-1 for up to 24 hours, lysed, and fractionated into cytosolic, nuclear, and insoluble portions. Proteins from the cytosolic fraction were further separated using a new batch ion-exchange chromatography method to reduce sample complexity, followed by two-dimensional (2D) electrophoresis, and identification of selected proteins by mass spectrometry. PDQuest software was utilized to identify and catalogue temporal changes in protein expression during IGF-1 stimulation. In response to IGF-1 stimulation, expression of 23 proteins increased at least three-fold and expression of 17 proteins decreased at least three-fold compared with control un-stimulated C2C12 cells. Changes in expression of selected proteins from each group, including Rho-GDI, cofillin, RAD50, enolase, IκB kinase b (IκBKb) and Hsp70 were confirmed by Western blotting. Additionally, the position of 136 'landmark' proteins whose expression levels and physicochemical properties did not change appreciably or consistently during IGF-1 treatment were mapped and identified. This characterization of large-scale changes in protein expression in response to growth factor stimulation of C2C12 cells will further help to establish a comprehensive understanding of the networks and pathways involved in the action of IGF-1.

A miniature condition in Brahman cattle is associated with a single nucleotide mutation within the growth hormone gene

Miniature Brahman cattle at the USDA ARS Subtropical Agriculture Research Station in Brooksville, FL have normal proportioned growth but are approximately 70% of mature height and weight when compared with Brahman cattle in the same herd. Pedigree analyses suggest that the condition is inherited through a recessive allele. The miniature Brahman cattle in the Brooksville herd have been used for studies of growth and reproduction, but the underlying causative mutation is unknown. Presumably, the miniature condition could arise from a mutation in the GH gene. The objective, therefore, was to clone the GH cDNA from Brooksville miniature Brahman cattle, compare its sequence to normal Brahman cattle, and test the biological activity of the native GH protein. Messenger RNA was isolated from the pituitary, and a cDNA for the protein coding region of the GH gene was amplified by reverse-transcription polymerase chain reaction (PCR) from each of 2 miniature Brahman bulls. The cDNA were cloned into plasmid vectors, and top and bottom strands were sequenced by automated DNA sequencing. The sequence of both cDNA clones derived from miniature cattle differed from Bos indicus GH (GenBank AF034386) at base number 641 because there was a cytosine (C) instead of a thymine (T). The C to T change encoded a mutation (threonine to methionine) at amino acid 200 (T200M mutation). The mutation was confirmed by sequencing of an additional 2 miniature cattle and comparing their sequence to 2 normal cattle. The threonine is located in the fourth alpha helix of GH and is 1 of 8 amino acids that participate in binding of GH to the GH receptor. Twelve miniature Brahman and 9 normal Brahman cattle were tested by using a restriction fragment length polymorphism analysis that employed the BsmBI restriction enzyme (specific for the mutated nucleotide). The 12 miniature Brahman cattle were homozygous for the mutation (-/-). Seven of the normal Brahman cattle were homozygous for the wild-type allele (+/+), and 2 were heterozygous (+/-). When tested in a cell-based bioassay, GH isolated from the pituitary of -/- cattle (n=4) had approximately 60% activity when compared with GH isolated from the pituitary of +/+ cattle (n=5). In summary, miniature Brahman cattle were homozygous for a single nucleotide polymorphism that encodes a mutation in an amino acid involved in binding of GH to the GH receptor. Cattle of normal size had at least 1 copy of the normal GH allele. Threonine 200 in bovine GH is required for normal growth in cattle.

Mutation analysis of the muscarinic cholinergic receptor genes in isolated growth hormone deficiency type IB

BACKGROUND

Isolated GH deficiency (IGHD) is familial in 5-30% of patients. The most frequent form (IGHD-IB) has autosomal recessive inheritance, and it is known that it can be caused by mutations in the GHRH receptor (GHRHR) gene or in the GH gene. However, most forms of IGHD-IB have an unknown genetic cause. In normal subjects, muscarinic cholinergic stimulation causes an increase in pituitary GH release, whereas its blockade has the opposite effect, suggesting that a muscarinic acetylcholine receptor (mAchR) is involved in stimulating GH secretion. Five types of mAchR (M(1)-M(5)) exist. A transgenic mouse in which the function of the M(3) receptor was selectively ablated in the central nervous system has isolated GH deficiency similar to animals with defective GHRH or GHRHR gene.

OBJECTIVE

We hypothesized that mAchR mutations may cause a subset of familial IGHD.

PATIENTS/METHODS

After confirming the expression of M(1)-M(5) receptor mRNA in human hypothalamus, we analyzed the index cases of 39 families with IGHD-IB for mutations in the genes encoding for the five receptors. Coding sequences for each of the five mAchRs were subjected to direct sequencing.

RESULTS

In one family, an affected member was homozygous for a M(3) change in codon 65 that replaces valine with isoleucine (V65I). The V65I receptor was expressed in CHO cells where it had normal ability to transmit methacholine signaling.

CONCLUSION

mAchR mutations are absent or rare (less than 2.6%) in familial IGHD type IB.

Role of corticotropin-releasing hormone testing in assessment of hypothalamic-pituitary-adrenal axis function in infants with congenital central hypothyroidism

CONTEXT

The Dutch neonatal congenital hypothyroidism (CH) screening program detects infants with CH of central origin (CH-C). These infants have a high likelihood of multiple pituitary hormone deficiencies. ACTH deficiency especially poses an additional risk for brain damage and may be fatal.

OBJECTIVE

Our objective was to evaluate different tools for assessment of the integrity of the hypothalamus-pituitary-adrenocortex (HPA) axis in young infants, aiming for a strategy for reliable and timely diagnosis.

DESIGN, SETTING

This is a Dutch nationwide prospective study (enrollment 1994-1996). Patients were included if neonatal CH screening results were indicative of CH-C and HPA axis function could be tested within 6 months of birth.

PATIENTS

Nine male and three female infants with CH-C and four infants with false-positive screening results or transient hypothyroidism were included in the study.

MAIN OUTCOME MEASURES

CRH test results, multiple cortisol plasma concentrations, and cortisol excretion in 24-h urine were measured.

RESULTS

Six (50%) of the CH-C patients had abnormal CRH test results. Three of them had discordant test results: impaired increase of plasma cortisol in response to CRH, despite substantial increase of plasma ACTH. The other three infants, with concordant impaired responses of both ACTH and cortisol to CRH, had a very low urinary cortisol excretion in comparison with the subjects with normal CRH test results.

CONCLUSIONS

The CRH test proves to be a fast and reliable tool in the assessment of HPA axis (dys)function. It enables timely diagnosis in (asymptomatic) neonates at risk for serious morbidity and mortality. The discordant response type, which has not been described before, may be an early phase of HPA axis dysfunction. Alternatively, patients with this response type may constitute a separate pathogenetic subset of HPA axis-deficient patients.

Hyperthermia and acidification stimulate mechano-growth factor synthesis in murine myoblasts and myotubes

The effect of cellular stress factors, the hyperthermia and the acidification of culture medium, on mechano-growth factor (MGF) synthesis by murine myoblasts in culture was investigated. Hyperthermia was shown to stimulate MGF expression both in primary myoblasts and in differentiated multinuclear myotubes. The induction of MGF synthesis peaked at 40 degrees capital ES, Cyrillic, with some activation at 39 and 41 degrees capital ES, Cyrillic. Decrease of culture medium pH stimulated MGF expression with a maximum at pH 6.3. Hydrocortisone eliminated induction of MGF synthesis completely both under hyperthermia and acidification conditions.

A functional common polymorphism in the vitamin D-responsive element of the GH1 promoter contributes to isolated growth hormone deficiency

CONTEXT

Causal mutations have been detected only in a minority of isolated GH deficiency (IGHD) patients. Idiopathic IGHD might be the result of the interaction between several low-penetrance genetic factors and the environment.

OBJECTIVE

The aim of this study was to test the contribution to IGHD of genetic variations in the GH1 gene regulatory regions.

DESIGN AND PATIENTS

A case-control association study was performed including 118 sporadic IGHD patients with a nonsevere phenotype (height -4/-1 sd score and partial GH deficiency) and two control groups, normal stature (n=200) and short-stature individuals with normal GH secretion (n=113). Seven single-nucleotide polymorphisms in the GH1 promoter, one in the IVS4 region, and two in the locus control region were analyzed.

RESULTS

The -57T allele within the vitamin D-responsive element showed a positive significant association when comparing patients with normal (P=0.006) or short stature (P=0.0011) controls. The genotype -57TT showed an odds ratio of 2.93 (1.44-5.99) and 2.99 (1.42-6.31), respectively. The functional relevance of the -57 variation was demonstrated by the luciferase assay in the presence of vitamin D. The vitamin D-induced inhibition of luciferase activity was significantly (P=0.012) stronger for the promoter haplotype carrying the associated variation -57T [haplotype #1 (hp#1)] with respect to hp#2, bearing -57G. Replacement of the T with a G at -57 on hp#1 abolished the repression, demonstrating that the T at position -57 is necessary to determine the greater vitamin D-induced inhibitory effect of hp#1. EMSA experiments showed a different band-shift pattern of the T and G sequences.

CONCLUSION

The common -57G-->T polymorphism contributes to IGHD susceptibility, indicating that it may have a multifactorial etiology.

Regulation of fetal growth: consequences and impact of being born small

The first trimester of pregnancy is the time during which organogenesis takes place and tissue patterns and organ systems are established. In the second trimester the fetus undergoes major cellular adaptation and an increase in body size, and in the third trimester organ systems mature ready for extrauterine life. In addition, during that very last period of intrauterine life there is a significant increase in body weight. In contrast to the postnatal endocrine control of growth, where the principal hormones directly influencing growth are growth hormone (GH) and the insulin-like growth factors (IGFs) via the GH-IGF axis, fetal growth throughout gestation is constrained by maternal factors and placental function and is coordinated by growth factors. In general, growth disorders only become apparent postnatally, but they may well be related to fetal life. Thus, fetal growth always needs to be considered in the overall picture of human growth as well as in its metabolic development.

Exon splice enhancer mutation (GH-E32A) causes autosomal dominant growth hormone deficiency

CONTEXT AND OBJECTIVE

Alteration of exon splice enhancers (ESE) may cause autosomal dominant GH deficiency (IGHD II). Disruption analysis of a (GAA) (n) ESE motif within exon 3 by introducing single-base mutations has shown that single nucleotide mutations within ESE1 affect pre-mRNA splicing.

DESIGN, SETTING, AND PATIENTS

Confirming the laboratory-derived data, a heterozygous splice enhancer mutation in exon 3 (exon 3 + 2 A-->C) coding for GH-E32A mutation of the GH-1 gene was found in two independent pedigrees, causing familial IGHD II. Because different ESE mutations have a variable impact on splicing of exon 3 of GH and therefore on the expression of the 17.5-kDa GH mutant form, the GH-E32A was studied at the cellular level.

INTERVENTIONS AND RESULTS

The splicing of GH-E32A, assessed at the protein level, produced significantly increased amounts of 17.5-kDa GH isoform (55% of total GH protein) when compared with the wt-GH. AtT-20 cells coexpressing both wt-GH and GH-E32A presented a significant reduction in cell proliferation as well as GH production after forskolin stimulation when compared with the cells expressing wt-GH. These results were complemented with confocal microscopy analysis, which revealed a significant reduction of the GH-E32A-derived isoform colocalized with secretory granules, compared with wt-GH.

CONCLUSION

GH-E32A mutation found within ESE1 weakens recognition of exon 3 directly, and therefore, an increased production of the exon 3-skipped 17.5-kDa GH isoform in relation to the 22-kDa, wt-GH isoform was found. The GH-E32A mutant altered stimulated GH production as well as cell proliferation, causing IGHD II.