Gene
HBA2
hemoglobin subunit alpha 2
- HGNC 4824(opens in a new tab)
- Ensembl gene ENSG00000188536(opens in a new tab)
- NCBI Gene 3040(opens in a new tab)
Summary
- Cytogenetic location
- 16p13.3
- Coordinates
- Chromosome 16: 172,876–173,710 (GRCh38)
- Exons
- 3 exons across 0.8 kb
- Protein
- 142 amino acids
- Inheritance
- Autosomal dominant
- Also known as
- HBA-T2
- MANE Select transcript
- ENST00000251595.11NM_000517.6
- Locus type
- gene with protein product
- Very high
- Confident
- Low
- Very low
Reference genomeGRCh38hg38
Positions on gene and variant pages follow this choice, in this browser.
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Get my Genome TestCurated reports relevant to this gene
Hereditary Methaemoglobinaemia and Unstable Haemoglobins
- Heinz Body AnaemiaAutosomal dominant
A dominant form of haemolytic anaemia in which unstable haemoglobin forms clumps (Heinz bodies) inside red cells.
- 1 GenCC submitter rates it definitive or strong
What knowing changes
Knowing about it helps avoid oxidant medicines that can worsen haemolysis.
Polycythemia
- Familial Erythrocytosis 7 (High-Oxygen-Affinity Haemoglobin, HBA1/HBA2)Autosomal dominant
A dominant form of inherited erythrocytosis caused by alpha-globin variants that make haemoglobin hold on to oxygen too tightly, so the body makes more red cells to compensate.
- 2 GenCC submitters rate it definitive or strong
What knowing changes
Knowing the inherited cause avoids it being mistaken for polycythaemia vera or other acquired causes, and spares unnecessary investigations.
Thalassaemia
- Thalassemia
A group of inherited haemoglobin disorders caused by reduced or absent synthesis of alpha- or beta-globin chains.
- ClinGen rates the link definitive
- 4 GenCC submitters rate it definitive or strong
What knowing changes
Transfusion and iron chelation (thalassemia major); hydroxyurea; betibeglogene autotemcel (Zynteglo) and exagamglogene autotemcel (Casgevy) gene therapy for transfusion-dependent disease; hematopoietic stem cell transplantation
Inheritance
- Autosomal dominant
- One changed copy, from either parent, is enough. A parent who has one passes it on to each child with a one-in-two chance.
How HBA2 is laid out
- Coding sequence
- Untranslated region
- Intron
- Direction of transcription
- Known disease-causing sites
- Stretches short reads find hard
- Variants with a page
Exons of the gene's MANE Select transcript (release v1.5), from NCBI and EMBL-EBI, on the GRCh38 reference genome.
Chromosome bands from UCSC's GRCh38 ideogram (2022-10-29).
Nearby genes from Ensembl release 116, on GRCh38.
Exons make up 0.6 kb of the gene's 0.8 kb; 429 of those bases code for the protein.
How a genome test reads HBA2
129
positions in HBA2 where ClinVar classes a change as pathogenic or likely pathogenic
129 of them (100%) fall in regions short reads find hard.
- Low mappability (113 sites)Regions where 100 bp or 250 bp reads cannot be placed uniquely.
- Segmental duplications (129 sites)Copies of at least 1 kb sharing at least 90% identity with another part of the genome (paralogues, pseudogenes); reads may align to the wrong copy.
A whole genome covers all 0.8 kb of HBA2, introns included, not only the 0.6 kb of exons.
Variants with a page (8)
The HBA2 variants with a page here, most review stars first. Each page describes ClinVar's public record of the variant, never a result.
| Variant | HGVS c. | Exon or intron | Position (GRCh38) | ClinVar classification | Review status |
|---|---|---|---|---|---|
| c.*92A>G | Exon 3 | 173,692 | Pathogenic | 3 stars out of 4 reviewed by expert panel | |
| c.2del | Exon 1 | 172,913 | Pathogenic | 3 stars out of 4 reviewed by expert panel | |
| c.93_95+2del | Exon 1 | 173,004 | Pathogenic | 3 stars out of 4 reviewed by expert panel | |
| C105R | c.313T>C | Exon 3 | 173,484 | Likely pathogenic | 3 stars out of 4 reviewed by expert panel |
| G60D | c.179G>A | Exon 2 | 173,208 | Pathogenic | 3 stars out of 4 reviewed by expert panel |
| L30P | c.89T>C | Exon 1 | 173,001 | Pathogenic | 3 stars out of 4 reviewed by expert panel |
| L126R | c.377T>G | Exon 3 | 173,548 | Likely pathogenic | 3 stars out of 4 reviewed by expert panel |
| X143Qext*31 | c.427T>C | Exon 3 | 173,598 | Pathogenic | 3 stars out of 4 reviewed by expert panel |
Traits linked to HBA2
The Human Phenotype Ontology lists these as features of the rare conditions HBA2 can cause. Each trait's page lists the other genes linked to it.
External links
Gene records
Transcript
Protein
Where this comes from
- HGNC: the gene's symbol, name, other symbols and location.
- MANE Select v1.5, from NCBI and EMBL-EBI: the transcript, its exons and coding sequence.
- GenCC and ClinGen, released 2026-10-16: which conditions the gene is linked to, and how strongly.
- The ACMG secondary findings list, SF v3.2.
- ClinVar and the GIAB stratifications: known disease-causing sites, and the regions short reads find hard.
- The Human Phenotype Ontology, release 2026-09-01: the traits linked to the gene. Find out more at hpo.jax.org.
- Data release 2026.10.16-c6eea6bf.
Cite this page
Dante Labs. (n.d.). HBA2 gene: hemoglobin subunit alpha 2. Retrieved 16 October 2026, from https://dantelabs.com/genes/hba2
Dante Labs. HBA2 gene: hemoglobin subunit alpha 2 [Internet]. [cited 16 October 2026]. Available from: https://dantelabs.com/genes/hba2
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