GENE REFERENCE / HGNC:11653

TCN2

transcobalamin 2

protein-coding gene22q12.2Gene information

What does this gene do?

The TCN2 gene provides instructions for making a protein called transcobalamin (formerly known as transcobalamin II). This protein transports cobalamin (also known as vitamin B12) from the bloodstream to cells throughout the body. Cobalamin is obtained from the diet; this vitamin is found in animal products such as meat, eggs, and shellfish.

During digestion, cobalamin is transported through intestinal cells into the bloodstream. Transcobalamin attaches (binds) to cobalamin when it is released into the bloodstream and transports the vitamin to cells. The transcobalamin-cobalamin complex binds to a receptor on the cell surface, which allows the complex to enter the cell. Transcobalamin releases cobalamin when the complex enters the cell and transcobalamin is broken down.

Within cells, cobalamin helps certain enzymes carry out chemical reactions. Cobalamin plays a role in the processes that produce the building blocks of DNA (nucleotides) and break down various compounds such as fatty acids; these processes are needed for cell growth and division (proliferation) and cellular energy production. Cobalamin's role in these processes is particularly important in the formation of new blood cells and in the nervous system.

Source: MedlinePlus, National Library of Medicine. Source publication: 2020-08-18. Source review: 2014-10.

ClinGen reviews

ClinGen reviews the evidence linking a particular gene to a condition. Each rating below describes the strength of that link. It does not classify a variant in your DNA file.

Condition	Inheritance	Evidence
transcobalamin II deficiencyMONDO:0010149 · Evaluated 2025-08-21	Autosomal recessive	DefinitiveSCID-CID Gene Curation Expert Panel

ClinVar records

These numbers show what has been submitted to ClinVar. They cannot tell you how likely you are to have a condition.

Submitted alleles: 840
Submissions for variants in or overlapping this gene: 1,224
Submissions explicitly reporting this gene: 1,185
Alleles reported pathogenic / likely pathogenic: 78
VariationIDs with uncertain significance: 271
VariationIDs with conflicting classifications: 30

The rows count different things: alleles, submissions or VariationIDs. Their categories can overlap, so do not add them together. Pathogenic/likely pathogenic counts exclude structural variants that merely overlap a gene. A dash in the source means “not reported,” not zero.

NCBI produces the gene-summary file each week using counts recorded at the start of the month. The numbers may differ from those on the live ClinVar website. Read the field definitions ↗

View this gene in ClinVar ↗

YOUR DNA FILE

Can your DNA file tell you about TCN2?

From a DNA test kit (such as 23andMe, AncestryDNA or MyHeritage). These kits check a fixed list of about 600,000 to 700,000 positions across your whole genome. ClinVar lists 78 alleles in TCN2 reported as pathogenic or likely pathogenic. A kit checks only some of these positions, and often none of them.

From whole genome sequencing (a VCF file). Sequencing reads most of your genome. Your file lists the places where your DNA differs from the reference genome. Some regions are hard to sequence, including parts of some genes that have near-identical copies elsewhere, and a VCF file does not record which positions were read well.

If a variant is not in your file, that does not mean you don’t have it.

What BioDecode checks

BioDecode compares every variant in your file with ClinVar, on your own computer. For each match, it shows the ClinVar classification, the review status and the condition it was reported for. Your file is not uploaded.

A ClinVar classification applies to one particular variant and the condition it was reported for. It does not tell you about other variants in TCN2.

BioDecode cannot fill gaps in your test, diagnose a condition or replace clinical testing.

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