Alternate Organization of α G-Philadelphia Globin Genes Among U.S. Black and Italian Caucasian Heterozygotes

Abstract

Seven Hb G-Philadelphia (Hb G) heterozygotes from three Caucasian families from Northern Italy and Sar-degna were found to have proportions of Hb G averaging 23%. This value is considerably lower than the 34% or 48% found in Blacks from the Southeastern U.S.A. in whom the α^G gene is in linkage with α-thalassernia-2, i.e. the α d` α<sup>G</sup>/αα or αd`α^G/αd` α genotypes, Gene mapping identified tandem organization of the α^G gene in cis with a normal α^A gene, i.e. the αα^G/αα genotype, among the Hb G heterozygotes from Italy. The data on the Italian heterozygotes are similar to those obtained by Bruzdzinski et a1 (14) on a Black family. These results indicate alternate organization of the α^G genes probably across racial or ethnic boundaries. Comparison of the mean cellular globin amount of α^G/α^G gene/cell among Hb G heterozygotes with 4, 3, 2 or 1 α globin genes (i.e. α^A + α^G) revealed considerable reactivation of individual α genes in conditions of mild to severe α globin deficiencies.