MOLECULAR CHARACTERIZATION OF Hb D-IBADAN [β87(F3)Thr→Lys] IN COMBINATION WITH Hb S [β(A3)Glu→Val] AND WITHβ⁺-THALASSEMIA: REPORT OF TWO CASES

Abstract

Hb D-Ibadan [beta87(F3)Thr-->Lys] is a common variant in the Nigerian population, which has been reported in association with Hb S [beta6(A3)Glu-->Val] and with beta-thalassemia. Unlike the Hb S/Hb D-Los Angeles [beta121(GH4)Glu-->Gln] combination, compound heterozygosity for Hb D-Ibadan and Hb S does not result in a sickling disorder. We report the first case of a combination of Hb D-Ibadan with beta+-thalassemia, and the first observation of Hb S/Hb D-Ibadan in the African-American population. In both cases, the characterization of Hb D-Ibadan was achieved by sequencing of the genomic DNA. Although protein based methods such as isoelec-trofocusing and high performance liquid chromatography may suggest that the "D-like" variant is different from Hb D-Los Angeles, the definitive identification of the variant by structural analysis or molecular genetic methods should be undertaken, particularly in newborn screening programs when the variant is found in combination with Hb S.

A New Sickling Variant ‘Hb S-Wake β[(Glu6Val-Asn139 Ser)]’ Found in a Compound Heterozygote with Hb S β(Glu6Val) Coinherited with Homozygous α-Thalassemia-2: Phenotype and Molecular Characteristics

“…Polymerase chain reaction (PCR) amplification and sequencing of the PCR products of the β-globin gene were performed on the DNA of the parents and of the patient using a previously described method [6]. Detection of α + -thalassemia (–α 3.7 ) was performed using PCR methods as previously described [7].…”

Neonatal Cyanosis Due to a Novel Fetal Hemoglobin: Hb F-Circleville [Gγ63(E7)His→Leu, CAT>CTT]

“…Table 1 shows the list of primers. Polymerase chain reaction was performed on each DNA sample, using target-specific primers for the G γ and A γ genes, and sequenced with region-specific primers by using the modified methods described before (9).…”