GENE REFERENCE / HGNC:7127

MLH1

mutL homolog 1

protein-coding gene3p22.2Gene information

What does this gene do?

The MLH1 gene provides instructions for making a protein that plays an essential role in repairing DNA. This protein helps correct errors that are made when DNA is copied in preparation for cell division, a process called DNA replication. The MLH1 protein joins with another protein called PMS2 to form a two-protein complex called a dimer. This complex coordinates the activities of other proteins that are involved in repairing errors made during DNA replication. The section of DNA that contains an error is removed and replaced with a corrected DNA sequence.

The MLH1 gene is one of a set of genes called mismatch repair (MMR) genes. The MLH1 protein can also form a dimer with the MLH3 or PMS1 protein, but the function of these dimers is not well understood.

Source: MedlinePlus, National Library of Medicine. Source publication: 2025-05-12. Source review: 2025-05.

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
Lynch syndromeMONDO:0005835 · Evaluated 2022-06-20	Autosomal dominant	DefinitiveHereditary Cancer Gene Curation Expert Panel
mismatch repair cancer syndrome 1MONDO:0010159 · Evaluated 2018-10-09	Autosomal recessive	DefinitiveHereditary Cancer Gene Curation Expert Panel
hereditary breast carcinomaMONDO:0016419 · Evaluated 2023-12-21	Autosomal dominant	RefutedHereditary Cancer 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: 6,511
Submissions for variants in or overlapping this gene: 17,816
Submissions explicitly reporting this gene: 17,754
Alleles reported pathogenic / likely pathogenic: 2,103
VariationIDs with uncertain significance: 2,187
VariationIDs with conflicting classifications: 530

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 MLH1?

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 2,103 alleles in MLH1 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 MLH1.

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

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