Islet amyloid polypeptide (IAPP) gene analysis in a Japanese diabetic with marked islet amyloid deposition.

Islet amyloid polypeptide (IAPP) is a major constituent of pancreatic amyloid deposits in many patients with non-insulin-dependent diabetes mellitus (NIDDM). We analyzed the IAPP gene in a Japanese diabetic with marked islet amyloid deposition. Pancreatic specimens were obtained from an 87-year-old NIDDM patient who had had diabetes for 37 years. All islets (100/100) in his pancreas had IAPP-positive amyloid deposition, and 70% of the area of the islet was replaced by amyloid. We amplified the coding regions as well as the upstream region of the IAPP gene by polymerase chain reaction (PCR). The products of PCR were sequenced, and the sequences of the coding regions were identical to the Caucasian ones. However, the nucleotides of two positions of 5'-upstream and one position of intron 2 were different from the Caucasian data: the upstream region of the IAPP gene in the patient had cytosine substituted for thymine at -259, and had two alleles including cytosine and adenine at -229, respectively. The nucleotide of position 539, that is guanine, was deleted. A possible difference in the IAPP promoting region between the Japanese and Caucasian population was suggested.