Growth hormone receptor polymorphisms.

Many variables influence the outcome of growth hormone (GH) therapy (GH dose and duration, height - SDS at treatment start or at puberty onset, bone age, mid parental height, growth velocity, age, etc.). Nevertheless, all these factors only partially explain the interindividual variability in response to GH in GH deficiency (GHD) and in short non-GHD subjects. To this regard, genes coding for factors involved in GH action could play an important role. GH acts through the GH receptor (GHR), and therefore the GHR gene could be the first candidate to influence the response to GH. Polymorphisms of the GHR have been described in exons 3, 6 and 10. The first one consists in the deletion (d3) or retention (fl) of the entire exon 3. The d3 polymorphism has been recently associated with a better growth response to GH in idiopathic short stature subjects and in short children born small for gestational age. Subsequent studies on the same and other categories of short children (idiopathic short stature, small for gestational age, GHD, Turner syndrome) have reported controversial results, with some confirming the role of d3 and others showing no effect. This review analyses these studies trying to explain the apparent discrepancies, mainly due to different selection criteria and different dose regimens in treating GHD and non-GHD short subjects.

Cytokine-mediated signalling and early defects in lymphoid development.

PURPOSE OF REVIEW: The aim of the review is to report on recent advances in cytokine-mediated signalling, as illustrated by the study of natural human mutants. In particular, the role of cytokines and cytokine-mediated signalling in human T-cell development is analysed in detail, and currently available forms of treatment including experimental trials are described. RECENT FINDINGS: Defects of the cytokine/JAK/STAT axis have been recently described as responsible for human Severe Combined Immune Deficiency. In particular, defects in gammac, JAK3 and IL7RA have been analysed in terms of development of novel diagnostic tools as well as of new therapeutic agents for the treatment of autoimmune diseases and graft-versus-host disease. SUMMARY: Dissection of the genetic defects underlying the various forms of Severe Combined Immune Deficiency has helped develop new and more accurate diagnostic assays and novel forms of treatment.

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.

Mutations of the Wiskott-Aldrich Syndrome Protein (WASP): hotspots, effect on transcription, and translation and phenotype/genotype correlation.

The Wiskott-Aldrich syndrome (WAS) is an X-linked recessive immune deficiency disorder characterized by thrombocytopenia, small platelet size, eczema, recurrent infections, and increased risk of autoimmune disorders and malignancies. X-linked thrombocytopenia (XLT) is an allelic variant of WAS which presents with a milder phenotype, generally limited to thrombocytopenia. WAS and XLT are caused by mutations of the Wiskott-Aldrich syndrome protein (WASP) gene which encodes a 502-amino acid protein, named WASP. WASP is thought to play a role in actin cytoskeleton organization and cell signaling. Here, we report the identification of 141 unique mutations, 71 not previously reported, from 227 WAS/XLT families with a total of 262 affected members. When possible we studied the effects of these mutations on transcription, RNA splicing, and protein expression. By analyzing a large number of patients with WAS/XLT at the molecular level we identified 5 mutational hotspots in the WASP gene and have been able to establish a strong association between genotype and phenotype.