GENE REFERENCE / HGNC:26169

CTC1

CST telomere replication complex component 1

protein-coding gene17p13.1Gene information

What does this gene do?

The CTC1 gene provides instructions for making a protein that plays an important role in structures known as telomeres, which are found at the ends of chromosomes. Telomeres are short, repetitive segments of DNA that help protect chromosomes from abnormally sticking together or breaking down (degrading). In most cells, telomeres become progressively shorter as the cell divides. After a certain number of cell divisions, the telomeres become so short that they trigger the cell to stop dividing or to self-destruct (undergo apoptosis).

The CTC1 protein works as part of a group of proteins known as the CST complex, which is involved in the maintenance of telomeres. This complex is part of the special machinery that some cells use to copy (replicate) telomeres so they do not become too short as cells divide. Studies suggest that the CTC1 protein may also have roles in DNA replication unrelated to telomeres, but these functions are not well understood.

Source: MedlinePlus, National Library of Medicine. Source publication: 2020-08-18. Source review: 2014-04.

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
cerebroretinal microangiopathy with calcifications and cysts 1MONDO:0024564 · Evaluated 2026-02-02	Autosomal recessive	DefinitiveLeukodystrophy and Leukoencephalopathy 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: 1,786
Submissions for variants in or overlapping this gene: 3,069
Submissions explicitly reporting this gene: 2,986
Alleles reported pathogenic / likely pathogenic: 156
VariationIDs with uncertain significance: 868
VariationIDs with conflicting classifications: 87

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 CTC1?

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 156 alleles in CTC1 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 CTC1.

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

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