Identification of four novel δ-globin gene mutations in Greek Cypriots using polymerase chain reaction and automated fluorescence-based DNA sequence analysis

Abstract

The molecular basis of most β-thalassemia syndromes has been defined, while the spectrum of mutations causing δ-thalassemia is not well characterized. In an attempt to identify such mutations, the region encompassing the 8-globin gene from three Greek Cypriot families suspected of having δ-thalassemia was amplified by polymerase chain reaction (PCR), and DNA sequence determined using an automated fluorescence-based sequencer. Four novel mutations were identified: a G → T change at codon 27 that results in an alanine to serine change; a C → T change at codon 116 converting arginine to cysteine; a T → C change at codon 141 converting leucine to proline; and an AG → GG change at the consensus 3′ -acceptor site in IVS-2. While the latter is clearly a thalassemic mutation, the low hemoglobin A2 in the first three may be due to either decreased production or instability of the altered δ-globin chain. All four mutations may be detected by PCR amplification of genomic DNA followed by restriction enzyme digestion. Two mutations abolish restriction sites while two create new cleavage sites. Screening for molecular defects that cause δ-thalassemia or unstable δ-globin by PCR amplification and restriction enzyme digestion will lead to correct diagnosis of β/δ-thalassemia compound heterozygotes and improved genetic counseling. © 1991 by The American Society of Hematology.