Identification of novel C253Y missense and Y864X nonsense mutations in the insulin receptor gene in type A insulin‐resistant patients

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Abstract
Mutations in the insulin receptor gene have been reported in cases of type A insulin resistance. We report herein two cases of type A insulin resistance, which involve some novel mutations. Case 1 is a heterozygote of the C253Y missense mutation and case 2 is a heterozygote of the Y864X nonsense mutation. In the C253Y missense mutation in exon 3, a cysteine residue is replaced with tyrosine in the cysteine‐rich domain of the α subunit. The Y864X in exon 13 results in a truncated receptor, which is devoid of most of the β subunit. This mutant receptor could not be expressed on a cell membrane since the transmembrane domain is missing. Other significant mutations were not found for the entire coding regions and splice/donor sites.