Alternate organization of α G-Philadelphia globin genes among US 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 αG gene is in linkage with αthalassernia-2, i.e. the α αG/αalpha; or αd̀αG/αd̀ α genotypes, Gene mapping identified tandem organization of the αGgene in cis with a normal αA gene, i.e. the αalpha;G/αalpha; genotype, among the Hb G heterozygotes from Italy. The data on the Italian heterozygotes are similar to those obtained by Bruzdzinski et al (14) on a Black family. These results indicate alternate organization of the αGgenes probably across racial or ethnic boundaries. Comparison of the mean cellular globin amount of αG/αG gene/cell among Hb Gheterozygotes with 4, 3, 2 or 1 α globin genes (i.e. αA + αG) revealed considerable reactivation of individual α genes in conditions of mild to severe α globin deficiencies.