Article

Genotype-phenotype correlation in inherited severe insulin resistance

Division of Medical Genetics, Department of Pediatrics, University of Utah, Salt Lake City 84103, USA.
Human Molecular Genetics (Impact Factor: 6.39). 06/2002; 11(12):1465-75.
Source: PubMed

ABSTRACT

The insulin receptor is a ligand-activated tyrosine kinase. Mutations in the corresponding gene cause the rare inherited insulin-resistant disorders leprechaunism and Rabson-Mendenhall syndrome. Patients with the most severe syndrome, leprechaunism, have growth restriction, altered glucose homeostasis and early death (usually before 1 year of age). Rabson-Mendenhall syndrome is less severe, with survival up to 5-15 years of age. These disorders are transmitted as autosomal recessive traits. Here we report six new patients and correlate mutations in the insulin receptor gene with survival. Patients with leprechaunism were homozygous or compound heterozygous for mutations in the extracellular domain of the insulin receptor and their cells had markedly impaired insulin binding (<10% of controls). Mutations in their insulin receptor gene inserted premature stop codons (E124X, R372X, G650X, E665X and C682X), resulting in decreased levels of mature mRNA, or affected the extracellular domain of the receptor (R86P, A92V, DeltaN281, I898T and R899W). Three patients with Rabson-Mendenhall syndrome had at least one missense mutation in the intracellular domain of the insulin receptor (P970T, I1116T, R1131W and R1174W). Expression studies in CHO cells indicated that the R86P, A92V, DeltaN281, I898T, R899W and R1131W mutations markedly impaired insulin binding (<5% of control), while the P970T, I1116T and R1174W mutant receptors retained significant insulin-binding activity. These results indicate that mutations in the insulin receptor retaining residual insulin-binding correlate with prolonged survival in our series of patients with extreme insulin resistance.

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    • "DNA from 11 unrelated individuals (7 controls and 4 patients with Leprechaunism) was used to determine performance characteristics of this INSR full gene sequencing assay. Of these four patients with Leprechaunism, three of them, referred to here as 452, NY1, and 5880, had previously been described [6] [7] [23] Fibroblasts from each of these patients were received and DNA was extracted by MagNA Pure. The fourth patient with Leprechaunism, SLC, was not previously described but fit the clinical criteria. "
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    ABSTRACT: Mutations in the insulin receptor gene cause the inherited insulin resistant syndromes Leprechaunism and Rabson–Mendenhall syndrome. These recessive conditions are characterized by intrauterine and post-natal growth restrictions, dysmorphic features, altered glucose homeostasis, and early demise. The insulin receptor gene (INSR) maps to the short arm of chromosome 19 and is composed of 22 exons. Here we optimize the conditions for sequencing this gene and report novel mutations in patients with severe insulin resistance.
    Full-text · Article · Dec 2014 · Molecular Genetics and Metabolism Reports
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    • "The α subunits mediate insulin binding and β subunits have tyrosine kinase activity (1). Insulin binds to the α subunit of the receptor and stimulates autophosphorylation and kinase activity of the β subunit (2). The human insulin receptor is coded by the gene INSR, and INSR mutations result in insulin resistance (3). "
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    ABSTRACT: Rabson-Mendenhall syndrome (RMS) is a rare syndrome manifested by extreme insulin resistance with hyperinsulinemia, acanthosis nigricans, tooth dysplasia and growth retardation. Our patient was first noted at the age of 8 months due to pigmentations on skin-folded areas. Initial laboratory tests showed normal fasting glucose (69 mg/dL). Fasting insulin level was severely elevated, up to 554.6 µIU/mL, and c-peptide level was increased, up to 13.81 ng/mL. However, hemoglobin A1c was within normal range (4.8%). He is now 11 yr old. His growth development followed the 5-10th percentile and oral hypoglycemic agents are being administered. The last laboratory results showed insulin 364.1 µIU/mL, C-peptide 4.30 ng/mL, and hemoglobin A1c 7.6%. The boy was a compound heterozygote for the c.90C > A and c.712G > A mutations of the insulin receptor gene, INSR, which are nonsense and missense mutations. In summary, we report the first Korean case of RMS, which was confirmed by two novel mutations of the INSR.
    Full-text · Article · May 2012 · Journal of Korean medical science
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    • "In one missense mutation, p.R1174W, an increase in receptor degradation leading to a reduced amount of receptor molecules was ob- served [3,19,20]. All reported cases of the Rabson–Mendenhall phenotype except for one are compound heterozygous for missense mutations located within the b subunit of the INSR gene affecting kinase activity and leading to mild decrease in insulin binding activity [3,8]. One patient was compound heterozygous for a missense mutation within the a subunit and for a nonsense-mutation within the b subunit [21]. "
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    ABSTRACT: Homozygous or compound heterozygous mutations within the insulin binding domain of the human insulin receptor (INSR) are usually associated with severe impairment of insulin binding leading to Donohue syndrome ("Leprechaunism"), which is characterized by excessive hyperglycemia with hyperinsulinism, pre- and postnatal growth retardation, distinct dysmorphism and early death. Missense mutations in the beta subunits are commonly associated with a milder impairment of insulin binding and milder phenotype with prolonged survival and less dysmorphism, the so called Rabson-Mendenhall syndrome. We report on a 13-year-old girl with Donohue syndrome like dysmorphism, hyperinsulinism and prolonged survival due to two novel INSR missense mutations within the insulin binding domain. Unexpectedly, insulin binding assays and investigations of activation of central insulin signaling pathways in fibroblasts revealed no significant alterations. Instead, immunofluorescence studies showed abnormal perinuclear distribution of the INSR alpha and beta subunits. Our data indicate that the quality of insulin binding activity is correlated with survival, not with the dysmorphic phenotype, and it is not always a valid parameter for predicting INSR mutations as proposed.
    Full-text · Article · Aug 2008 · Molecular Genetics and Metabolism
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