Haplotypes of β^S Chromosomes Among Patients with Sickle Cell Anemia from Georgia

Abstract

Fetal hemoglobin and ^Gγ levels have been correlated with the presence or absence of eight restriction sites within the β globin gene cluster (haplotypes) for numerous sickle cell anemia patients from Georgia. The most common haplotypes were #19 (Benin) and #20 (CAR); all patients with haplotype combinations 19/19, 20/20, and 19/20 were severely affected with low Hb F and low ^Gγ levels. A modified #19 β^S chromosome with a -^Gγ-^Gγ- globin gene arrangement, instead of -^Gγ-^Aγ-, was present in SS and SC newborn babies with ^Gγ values above 80%. Haplotype #3 (Senegal) was present among 15% of the β^S chromosomes; the two adult patients with the 3/3 combination were mildly affected with high Hb F and ^Gγ values. The haplotype A^T with the variant Aγ^T chain was a rarity. A new haplotype was found in one 17-year-old SS patient and five of his Hb S heterozygous relatives. This haplotype is associated with an increased production of Hb F in heterozygous and homozygous Hb S individuals; this Hb F contained primarily ^Aγ chains. A comparison was made between the different haplotypes among SS patients and normal Black individuals, and a remarkable similarity was noted in the fetal hemoglobin data for subjects with these different chromosomes.