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TF
transferrin
TF is located on the long (q) arm of chromosome 3, at band 3q22.1. Arm ratio per GRCh38 - banding schematic.
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Overview
The TF gene, located on chromosome 3, encodes transferrin - a plasma protein responsible for transporting iron throughout the body. Iron is essential for numerous biological processes, including haemoglobin synthesis in red blood cells and cellular energy production. Transferrin binds iron in the bloodstream and delivers it to cells via transferrin receptors on the cell surface.
Genetic variation in TF influences iron metabolism and forms part of polygenic risk models for iron-related disorders. Unlike single-gene conditions with clear inheritance patterns, TF variants contribute to disease susceptibility alongside multiple other genetic and environmental factors. The gene is included on several NHS clinical genomics panels focused on anaemia and iron metabolism disorders.
What the gene does
Transferrin serves as the primary iron carrier in human plasma, binding up to two ferric iron (Fe³⁺) ions per molecule. The protein circulates in blood and binds to transferrin receptors on the surface of cells that require iron, particularly developing red blood cells in the bone marrow. Following receptor binding, the transferrin-iron complex enters the cell through endocytosis, where iron is released in the acidic environment of the endosome.
Once iron is delivered, transferrin returns to circulation to bind additional iron released from dietary absorption or recycled from aged red blood cells. This cycling mechanism ensures efficient iron distribution whilst preventing free iron from catalysing harmful oxidative reactions. Transferrin saturation - the percentage of iron-binding sites occupied - serves as a key clinical marker of iron status. The protein also exhibits antimicrobial properties by sequestering iron away from pathogens that require this nutrient for growth.
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Chromosome location
The TF gene is located on the long arm of chromosome 3 at position 3q22.1. This chromosomal region contains several genes involved in metabolic regulation. The gene spans approximately 33.5 kilobases of genomic DNA and comprises 17 exons that encode the mature transferrin protein.
Protein structure
Transferrin is synthesised as a 698-amino-acid polypeptide. The mature protein consists of two homologous lobes, each capable of binding one iron atom. The Transferrin-like 1 domain spans amino acids 25-347, forming the N-terminal lobe, whilst the Transferrin-like 2 domain encompasses amino acids 361-683, constituting the C-terminal lobe. Each lobe contains a deep cleft where iron binding occurs, coordinated by specific amino acid residues including tyrosine, histidine, and aspartate. The two lobes are connected by a short peptide linker that allows conformational flexibility. Glycosylation sites on the protein surface contribute to stability and circulatory half-life.
Key variants
Genetic variation in TF encompasses both common polymorphisms and rare variants. Common variants contribute to normal population variation in transferrin levels and iron metabolism parameters. Rare pathogenic variants can disrupt transferrin synthesis or function, though such cases are uncommon. The polygenic nature of iron metabolism means that TF variants typically interact with variants in other iron-related genes to influence overall iron status and disease risk.
No pathogenic or likely-pathogenic ClinVar variants recorded yet for this gene.
Associated conditions
Variation in TF contributes to polygenic susceptibility for disorders affecting iron metabolism and red blood cell production. Unlike monogenic conditions caused by variants in a single gene, polygenic conditions arise from the cumulative effect of variants across multiple genes. TF variants may influence iron availability, which in turn affects red blood cell formation and can contribute to certain forms of anaemia. The gene's role is considered within the broader context of iron homeostasis, where factors including dietary intake, absorption efficiency, and storage capacity all interact.
No disease links recorded for this gene in our reference set.
UK clinical status
Within the NHS Genomic Medicine Service, TF appears on multiple clinical gene panels. The gene holds green classification status on the Cytopenias and Congenital Anaemias panel, the Iron Metabolism Disorders panel (excluding common HFE mutations, designated R96), and the Rare Anaemia panel (R92). Green classification indicates robust evidence supporting the gene-disease relationship and validates its inclusion in diagnostic testing pathways for patients presenting with relevant clinical features.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What does transferrin saturation measure?
Transferrin saturation indicates the percentage of transferrin molecules in blood that are carrying iron. It is calculated by dividing serum iron by total iron-binding capacity and reflects how much iron is available for delivery to tissues. Low saturation suggests iron deficiency, whilst elevated saturation may indicate iron overload.
How is TF different from genes like HFE?
Whilst both genes influence iron metabolism, HFE regulates iron absorption through its effects on hepcidin production, whereas TF encodes the transport protein that carries iron through the bloodstream. Variants in HFE can cause the monogenic condition hereditary haemochromatosis, whereas TF variants contribute to polygenic risk alongside multiple other factors.
Are TF variants tested routinely for iron disorders?
TF is included on NHS clinical gene panels for iron metabolism disorders and anaemias, meaning it may be analysed when clinicians request genomic testing for patients with unexplained iron abnormalities or specific forms of anaemia. Testing is guided by clinical presentation rather than being offered routinely to the general population.