Transthyretin Ile 122: Gene frequency and risk of cardiac amyloidosis in African Americans
- New York V.A. Medical Center, New York, NY (United States)
- New York Univ. School of Medicine, New York, NY (United States); and others
Point mutations in the protein transthyretin (TTR) cause familial amyloidosis involving mainly the heart and peripheral nerves. To determine the TTR Ile 122 gene frequency in African Americans, the allele encoding TTR Ile 122 was identified by PCR-Primer Introduced Restriction Analysis of TTR exon 4 and FokI digestion on 1659 control DNA samples from 1659 African Americans: 64 were heterozygous and one homozygous (allele frequency .02). To determine the risk to gene carriers of developing cardiac amyloidosis, immunohistochemical and genetic studies were performed on amyloid-containing samples identified among 52,370 autopsy samples examined over 32 years. In autopsy samples from patients over age 60, isolated cardiac amyloidosis was more common in African Americans (1.6%) than in White Americans (.40%), suggesting a genetic risk factor. All 29 samples from African Americans were immunohistochemically TTR-positive, and 5 were heterozygous for the TTR Ile 122 allele (17%), as compared with 5/108 heterozygotes (4.6%) among age-matched (over age 60) African American controls without amyloidosis from the same autopsy study (one-tailed P value < .03). Among the 29 amyloid-positive samples were 16 with 1+ or 2+ deposition and 13 with 3+ or 4+ deposition. All 5 TTR Ile 122 heterozygotes had 3+ or 4+ deposition. None of 15 samples from White Americans with cardiac amyloidosis was TTR Ile 122-positive. Extrapolating from the 5/29 samples from which we were able to obtain genetic data, we estimate that 9/54 samples containing cardiac amyloid were TTR Ile 122 heterozygotes. We conclude that heterozygosity for TTR Ile 122 is associated with a greater frequency (relative risk 5.8) and greater severity of cardiac amyloid deposition than in non-carriers of the TTR Ile 122 gene. Of over 40 TTR point mutations associated with amyloidosis described to date, TTR Ile 122 appears to be the most common worldwide and to have the lowest penetrance in causing disease.
- OSTI ID:
- 134178
- Report Number(s):
- CONF-941009-; ISSN 0002-9297; TRN: 95:005313-0914
- Journal Information:
- American Journal of Human Genetics, Vol. 55, Issue Suppl.3; Conference: 44. annual meeting of the American Society of Human Genetics, Montreal (Canada), 18-22 Oct 1994; Other Information: PBD: Sep 1994
- Country of Publication:
- United States
- Language:
- English
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