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J Clin Endocrinol Metab. 2007 Apr;92(4):1542-8. Epub 2007 Jan 30.

A familial insulin-like growth factor-I receptor mutant leads to short stature: clinical and biochemical characterization.

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1
Division of Endocrinology, Diabetes, and Bone Diseases, Department of Medicine, The Mount Sinai School of Medicine, New York, New York 10029, USA.

Abstract

CONTEXT:

IGF-I/IGF-I receptor (IGF-IR) signaling pathways play important roles in longitudinal growth. A novel Arg481Glu (R481Q) mutation in IGF-IR was detected in a family with intrauterine and postnatal growth retardation.

OBJECTIVE:

The objective of the study was to explore the mechanism whereby the R481Q mutation may be causative in growth retardation.

PATIENTS:

A 13-yr-old girl with short stature was studied for functional analysis of the R481Q mutation in the IGF-IR.

RESULTS:

Two members of a family who showed intrauterine and postnatal growth retardation, with increased serum IGF-I levels, demonstrated a substitution of arginine for glutamine at 481 (R481Q) in the IGF-IR. This mutation results in the formation of an altered fibronectin type III domain within the alpha-subunit. NIH-3T3 fibroblasts that overexpress the human wild-type or R481Q mutant IGF-IR demonstrated normal cell surface ligand binding by 125I-IGF-I binding assay. However, the fold increase of IGF-I stimulated tyrosine phosphorylation of the IGF-IR beta-subunit as well as downstream activation of ERK1/2 and Akt was reduced in cells overexpressing the mutant receptor. Additionally, basal and IGF-I-stimulated levels of cell proliferation were also reduced in cells overexpressing the mutant receptor.

CONCLUSION:

Our results demonstrate that NIH-3T3 cells overexpressing a mutant form of the Igf1r gene, in which arginine at 481 is substituted by glutamine, lead to reduced levels of the fold increase of IGF-IR beta-subunit phosphorylation as well as ERK1/2 and Akt phosphorylation and was accompanied by decreased cell proliferation. These results are postulated to be the cause of intrauterine and postnatal growth retardation in the described patients.

PMID:
17264177
DOI:
10.1210/jc.2006-2354
[Indexed for MEDLINE]
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