Blood, Vol. 92 No. 8 (October 15), 1998:
pp. 2959-2962
The Relationship of the 
5, 8, and 24 Variant Alleles in
African Americans to Triosephosphate Isomerase (TPI) Enzyme
Activity and to TPI Deficiency
Arthur Schneider,
Linda Forman,
Beryl Westwood,
Catherine Yim,
James Lin,
Satinder Singh, and
Ernest Beutler
From the Department of Pathology, Finch University of Health
Sciences/The Chicago Medical School, North Chicago, IL; the Department
of Molecular and Experimental Medicine, The Scripps Research Institute,
La Jolla, CA; and the Laboratory Service, Veterans Affairs Medical
Center, North Chicago, IL.
In 424 African-American and 75 white subjects, we found that the
5 (TPI 592 A
G), 8 (TPI 589 GA), and 24
(TPI 573 TG) variants in the triosephosphate isomerase (TPI)
gene occurred frequently (41.0%) in the African-American subjects but
did not occur in the whites. These data suggest that this set of
polymorphisms may turn out to be one of the higher-incidence molecular
markers of African lineage, a surprising finding because others had
reported that these nucleotide substitutions were restricted to a small subset of African Americans who had been characterized as
TPI-deficiency heterozygotes. Additionally, we investigated the
relationship of these variants to TPI-enzyme activity. Although the
variant substitutions (occurring in three haplotypes: 5 alone, 5
8, and 5 8 24) were associated with moderate reduction in
enzyme activity, severe-deficiency heterozygotes could not be
identified with certainty, and none of the haplotypes were restricted
to subjects with marked reduction of enzyme activity. Three subjects were homozygous for the 5 8 haplotype, a finding inconsistent with the putative role of this haplotype as the cause of a null variant
incompatible with life in homozygotes. Despite these findings, the
possibility remains that the 5 8 or 5 8 24 haplotypes may in some instances contribute to compound heterozygosity and clinical TPI deficiency.
© 1998 by The American Society of Hematology.
