IthaID: 3758

Names and Sequences

Functionality: Globin gene causative mutation Pathogenicity: Pathogenic / Likely Pathogenic
Common Name: CD 126 GAC>AAC [Asp>Asn] HGVS Name: HBA2:c.379G>A
Hb Name: Hb Tarrant Protein Info: α2 126(H9) Asp>Asn

Context nucleotide sequence:

Protein sequence:

Also known as:

Comments: Asparagine at α126 (or position 9 of the H-helix) is essential for the formation of a salt bond with the carboxy-terminal arginyl residue of the other α chain when the hemoglobin is deoxygenated. Its substitution for aspartic acid destabilizes the deoxy conformation. High oxygen affinity Hb variant, ranging from ~25% (heterozygotes) to ~50% (homozygote) of total Hb. Erythrocytosis with a blood P50 value of ~15.1 mm Hg (heterozygotes) down to ~9 mm Hg (homozygote) [PMID: 7019159]. The heterozygotes have mild erythrocytosis which is considerably more severe in the homozygote. Hb Tarrant was initially detected in a few Mexican families by protein analysis (HBA2 or HBA1 gene) and was later found by molecular analysis in HBA2 in another Mexican family, as well as a Chinese family.

We follow the HGVS sequence variant nomenclature and IUPAC standards.


Hemoglobinopathy Group: Structural Haemoglobinopathy
Hemoglobinopathy Subgroup: α-chain variant
Allele Phenotype:N/A
Stability: N/A
Oxygen Affinity: Increased Oxygen Affinity
Associated Phenotypes: N/A


Chromosome: 16
Locus: NG_000006.1
Locus Location: 34413
Size: 1 bp
Located at: α2
Specific Location: Exon 3

Other details

Type of Mutation: Point-Mutation(Substitution)
Effect on Gene/Protein Function: Missense codons (Protein Structure)
Ethnic Origin: Chinese, Mexican
Molecular mechanism: N/A
Inheritance: Recessive
DNA Sequence Determined: Yes

In silico pathogenicity prediction

Sequence Viewer

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Publications / Origin

  1. Moo-Penn WF, Jue DL, Johnson MH, Wilson SM, Therrell B, Schmidt RM, Hemoglobin Tarrant: alpha126(H9) Asp leads to Asn. A new hemoglobin variant in the alpha1beta1 contact region showing high oxygen affinity and reduced cooperativity., Biochim. Biophys. Acta , 490(2), 443-51, 1977 PubMed
  2. Ibarra B, Vaca G, Cantú JM, Wilson JB, Lam H, Stallings M, Gravely ME, Huisman TH, Heterozygosity and homozygosity for the high oxygen affinity hemoglobin Tarrant or alpha 126 (H9) Asp replaced by Asn in two Mexican families., Hemoglobin , 5(4), 337-48, 1981 PubMed
  3. Perea FJ, Zamudio G, Meillon LA, Ibarra B, The Hb Tarrant [alpha126(H9)Asp-->Asn]] mutation is localized in the alpha2-globin gene., Hemoglobin, 23(3), 295-7, 1999 PubMed
  4. Henderson SJ, Timbs AT, McCarthy J, Gallienne AE, Proven M, Rugless MJ, Lopez H, Eglinton J, Dziedzic D, Beardsall M, Khalil MS, Old JM, Ten Years of Routine α- and β-Globin Gene Sequencing in UK Hemoglobinopathy Referrals Reveals 60 Novel Mutations., Hemoglobin , 40(2), 75-84, 2016 PubMed
  5. Ip KaLingRosalina,So JasonChi-Chiu,Law Man-Fai,Wong RaymondSM,Tam HoChi,Ng MargaretHL, Hb Tarrant [α126(H9)Asp→Asn; HBA2: c.379G > A (or HBA1)] in a Chinese Family as a Cause of Familial Erythrocytosis., Hemoglobin, 4(4), 260-3, 2017 PubMed
Created on 2021-03-31 21:09:22, Last reviewed on 2023-11-09 11:28:09 (Show full history)

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