title: Hb Tak confirmed by DNA analysis: not expressed as thalassemia in a Hb Tak/Hb E compound heterozygote.
abstract: Hemoglobin variants in which a frameshift results in chain elongation are unusual and also have a low population frequency. Hb Tak was previously characterized by amino acid analysis, and it was assumed to be due to an insertion of the dinucleotide CA into codon 146 [CAC-->CA(CA)C] which abolishes the normal stop codon at position 147. This insertion causes a frameshift which results in elongation of the beta chain by 11 amino acids. This variant has previously been described in a few Thai families. We report the DNA sequence of Hb Tak in an individual of Cambodian descent who is a Hb E/Hb Tak compound heterozygote. In contrast with extended variants of the alpha-globin chain that are expressed as alpha-thalassemias, the hematologic effect of Hb Tak/Hb E is a mild polycythemia. The combination of Hb Tak/Hb E is not expressed as a thalassemia.
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Hoyer
authors.forename: M J
authors.initials: MJ
authors.lastname: Wick
authors.forename: S N
authors.initials: SN
authors.lastname: Thibodeau
authors.forename: K A
authors.initials: KA
authors.lastname: Viker
authors.forename: R
authors.initials: R
authors.lastname: Conner
authors.forename: V F
authors.initials: VF
authors.lastname: Fairbanks
mesh_terms: D000328:Adult; D019943:Amino Acid Substitution / Q000235:genetics; D002160:Cambodia / Q000208:ethnology; D006580:Genetic Carrier Screening; D018698:Glutamic Acid / Q000235:genetics; D006441:Hemoglobin A / Q000235:genetics; D006446:Hemoglobin E / Q000235:genetics*; D006455:Hemoglobins, Abnormal / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D008239:Lysine / Q000235:genetics; D008297:Male; D009154:Mutation; D017422:Sequence Analysis, DNA; D013789:Thalassemia / Q000097:blood* / Q000235:genetics*
chemical_list: D006455:Hemoglobins, Abnormal; C111400:hemoglobin Tak; D018698:Glutamic Acid; D006441:Hemoglobin A; D006446:Hemoglobin E; D008239:Lysine