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.

Evaluation of the biological activity of a growth hormone (GH) mutant (R77C) and its impact on GH responsiveness and stature

CONTEXT AND OBJECTIVE: A single missense mutation in the GH-1 gene converting codon 77 from arginine (R) to cysteine (C) yields a mutant GH-R77C peptide, which was described as natural GH antagonist. DESIGN, SETTING, AND PATIENTS: Heterozygosity for GH-R77C/wt-GH was identified in a Syrian family. The index patient, a boy, was referred for assessment of his short stature (-2.5 SD score) and partial GH insensitivity was diagnosed. His mother and grandfather were also carrying the same mutation and showed partial GH insensitivity with modest short stature. INTERVENTIONS AND RESULTS: Functional characterization of the GH-R77C was performed through studies of GH receptor binding and activation of Janus kinase 2/Stat5 pathway. No differences in the binding affinity and bioactivity between wt-GH and GH-R77C were found. Similarly, cell viability and proliferation after expression of both GH peptides in AtT-20 cells were identical. Quantitative confocal microscopy analysis revealed no significant difference in the extent of subcellular colocalization between wt-GH and GH-R77C with endoplasmic reticulum, Golgi, or secretory vesicles. Furthermore studies demonstrated a reduced capability of GH-R77C to induce GHR/GHBP gene transcription rate when compared with wt-GH. CONCLUSION: Reduced GH receptor/GH-binding protein expression might be a possible cause for the partial GH insensitivity with delay in growth and pubertal development found in our patients. In addition, this group of patients deserves further attention because they could represent a distinct clinical entity underlining that an altered GH peptide may also have a direct impact on GHR/GHBP gene expression causing partial GH insensitivity.

Catch-up growth in autosomal dominant isolated growth hormone deficiency (IGHD type II)

OBJECTIVE: Data on the GH-induced catch-up growth of severely GH-deficient children affected by monogenetic defects are missing. PATIENTS: Catch-up growth of 21 prepubertal children (6 females, 15 males) affected with IGHD type II was analyzed in a retrospective chart review. At start of therapy, mean age was 6.2 years (range, 1.6-15.0), mean height SDS was -4.7 (-7.6 to -2.2), mean IGF-I SDS was -6.2 (-10.1 to -2.2). GH was substituted using a mean dose of 30.5microg/kg*d. RESULTS: Catch-up growth was characterized by a mean height gain of +0.92, +0.82, and +0.61 SDS after 1, 2, and 3 years of GH therapy, respectively. Mean height velocities were 10.7, 9.2 and 7.7cm/year during the first three years. Mean duration of complete catch-up growth was 6 years (3-9). Mean height SDS reached was -0.97 (-2.3 to +1.1), which was within the range of the estimated target height of -0.60 SDS (-1.20 to -0.15). The younger and shorter the children were at start of therapy the better they grew during the first year independent of the dose. Mean bone age was delayed at start by 2.1 years and progressed by 2.5 years during the first two years of therapy. Incomplete catch-up growth was caused by late initiation or irregular administration of GH in four cases. CONCLUSIONS: Our data suggest that GH-treated children with severe IGHD show a sustained catch-up growth over 6 years (mean) and reach their target height range. This response to GH is considered to be characteristic for young children with severe growth retardation due to IGHD.

Genetics of growth hormone deficiency

When a child is not following the normal, predicted growth curve, an evaluation for underlying illness and central nervous system abnormalities is required and appropriate consideration should be given to genetic defects causing growth hormone (GH) deficiency. This article focuses on the GH gene, the various gene alterations, and their possible impact on the pituitary gland. Transcription factors regulating pituitary gland development may cause multiple pituitary hormone deficiency but may present initially as GH deficiency. The role of two most important transcription factors, POU1F1 (Pit-1) and PROP 1, is discussed.

Post-prandial alterations in LDL size and subclasses in patients with growth hormone deficiency

Several studies have suggested that lipoproteins generated during the post-prandial phase are highly atherogenic, with modifications in low-density lipoproteins (LDL) size and density. In the present study we assessed post-prandial variations in LDL size and subclasses in patients with growth hormone deficiency (GHD).

Atherogenic lipoprotein phenotype and low-density lipoprotein size and subclasses in patients with growth hormone deficiency before and after short-term replacement therapy

Patients with growth hormone deficiency (GHD) have increased cardiovascular risk and may show elevated triglyceride and reduced high density lipoprotein (HDL) cholesterol concentrations, two lipid abnormalities usually accompanied by increased small dense LDL in the 'atherogenic lipoprotein phenotype' (ALP). In the present study, we directly investigated (1) whether hypopituitary patients with GHD have increased small dense LDL; (2) whether growth hormone replacement therapy (GHRT) beneficially impact on such particles; (3) the prevalence of ALP in GHD and GHRT patients.