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EPB42
erythrocyte membrane protein band 4.2
EPB42 is located on the long (q) arm of chromosome 15, at band 15q15.2. Arm ratio per GRCh38 - banding schematic.
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Overview
The EPB42 gene encodes erythrocyte membrane protein band 4.2, a structural protein found in the membrane of red blood cells. This protein forms part of the membrane skeleton, a network of proteins that underlies the lipid bilayer and provides mechanical support. Protein 4.2 interacts with other membrane components to maintain the characteristic biconcave shape of red blood cells, which is essential for their function in oxygen transport. When EPB42 is altered by pathogenic variants, the membrane skeleton becomes unstable, resulting in red blood cells that are spherical rather than disc-shaped and prone to premature destruction.
What the gene does
Erythrocyte membrane protein band 4.2 serves as a bridging component within the red blood cell membrane skeleton, linking the spectrin-actin cytoskeleton to integral membrane proteins. The protein binds to ankyrin and the anion exchanger band 3, helping to anchor the membrane skeleton to the lipid bilayer. This interaction is critical for maintaining membrane cohesion and distributing mechanical forces across the cell surface during circulation through narrow capillaries. Protein 4.2 also modulates the activity of band 3, influencing anion transport across the membrane. By stabilising the connection between the cytoskeleton and the membrane, protein 4.2 ensures that red blood cells retain their flexibility and structural integrity throughout their lifespan in the bloodstream. Loss or dysfunction of this protein compromises the entire membrane architecture, leading to abnormal cell morphology and reduced cellular survival.
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Chromosome location
EPB42 is located on chromosome 15 at band 15q15.2. The gene spans a region in the long arm of chromosome 15, positioned between established markers in the 15q15 cytogenetic band. The specific chromosomal position places EPB42 within a gene-dense region, though the gene itself operates independently in erythrocyte membrane biology.
Protein structure
The EPB42 protein comprises 691 amino acids and contains a defined band 3 binding region spanning amino acids 31-39. This N-terminal binding motif mediates the direct interaction with the anion exchanger band 3, anchoring protein 4.2 to the membrane. The remaining structure supports binding to ankyrin and contributes to the overall stability of the membrane skeleton complex. Detailed domain architecture beyond the band 3 binding region has not been fully characterised experimentally.
Key variants
Pathogenic variants in EPB42 typically result in reduced or absent protein 4.2 expression. Most disease-causing changes are loss-of-function variants, including nonsense mutations, frameshift deletions, and splice-site alterations that disrupt normal protein production. The severity of clinical manifestations generally correlates with the degree of protein deficiency. Homozygous or compound heterozygous variants lead to more severe membrane instability compared to single heterozygous changes.
Sample of pathogenic variants
9 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.
| Variant (HGVS) | Protein change | Classification | Evidence | Associated condition |
|---|---|---|---|---|
c.775C>T | p.Arg259Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Hereditary spherocytosis type 5 |
c.1305C>G | p.Tyr435Ter | Pathogenic | ★☆☆☆ | Hereditary spherocytosis type 5 |
c.1423_1454del | p.Leu475fs | Pathogenic | ★☆☆☆ | Hereditary spherocytosis type 5 |
c.1641_1648del | p.Phe548fs | Pathogenic | ★☆☆☆ | not provided |
c.1660C>T | p.Arg554Ter | Pathogenic | ★☆☆☆ | not provided |
c.175del | p.Val59fs | Pathogenic | ★☆☆☆ | not provided |
c.433G>T | p.Asp145Tyr | Pathogenic | ★☆☆☆ | Hereditary spherocytosis type 5 |
c.1747G>T | p.Glu583Ter | Pathogenic | - | Hereditary spherocytosis type 5 |
c.922+1G>A | - | Pathogenic | - | Hereditary spherocytosis type 5 |
Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.
Associated conditions
Variants in EPB42 are associated with hereditary spherocytosis, an inherited disorder characterised by red blood cells with a spherical shape rather than the normal biconcave disc. The autosomal recessive form linked to EPB42 tends to present with more severe anaemia compared to dominant forms caused by variants in other membrane genes. Affected individuals may experience chronic haemolytic anaemia, jaundice, splenomegaly, and an increased risk of gallstones. The severity of hereditary spherocytosis varies depending on the specific EPB42 variants inherited and the resulting level of protein 4.2 deficiency.
Inheritance pattern
Conditions caused by pathogenic EPB42 variants typically follow autosomal recessive inheritance.
When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.
UK clinical status
EPB42 is classified with green status on the NHS Genomic Medicine Service National Genomic Test Directory panel for Cytopenias and Congenital Anaemias, indicating sufficient evidence for clinical diagnostic testing. The gene also appears on the Rare Anaemia panel with green status under test code R92. These designations reflect the established role of EPB42 variants in hereditary spherocytosis and support the use of genomic testing for individuals presenting with unexplained haemolytic anaemia or red blood cell membrane disorders.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What does the EPB42 gene do?
EPB42 provides instructions for making protein 4.2, a structural component of the red blood cell membrane that maintains cell shape and mechanical stability. The protein links the membrane skeleton to the lipid bilayer, ensuring red blood cells remain flexible during circulation.
How is EPB42-related hereditary spherocytosis inherited?
EPB42-related hereditary spherocytosis follows an autosomal recessive pattern, meaning an individual must inherit pathogenic variants in both copies of the gene to develop the condition. Carriers with one variant typically do not show symptoms.
Is EPB42 tested on the NHS?
Yes, EPB42 is included on NHS genomic testing panels for cytopenias and congenital anaemias with green classification status, indicating it is approved for diagnostic use in individuals with suspected hereditary red blood cell disorders.