MLH1

Chr 3ARAD

mutL homolog 1

Also known as: COCA2, FCC2, HNPCC, HNPCC2, LYNCH2, MLH-1, MMRCS1, hMLH1

The protein encoded by this gene can heterodimerize with mismatch repair endonuclease PMS2 to form MutL alpha, part of the DNA mismatch repair system. When MutL alpha is bound by MutS beta and some accessory proteins, the PMS2 subunit of MutL alpha introduces a single-strand break near DNA mismatches, providing an entry point for exonuclease degradation. The encoded protein is also involved in DNA damage signaling and can heterodimerize with DNA mismatch repair protein MLH3 to form MutL gamma, which is involved in meiosis. This gene was identified as a locus frequently mutated in hereditary nonpolyposis colon cancer (HNPCC). [provided by RefSeq, Aug 2017]

GeneReviewsOMIMResearchGenerating clinical summary…

Primary Disease Associations & Inheritance

Lynch syndrome 2MIM #609310
Mismatch repair cancer syndrome 1MIM #276300
AR
Muir-Torre syndromeMIM #158320
AD
UniProtEndometrial cancer
UniProtColorectal cancer

Clinical highlights

Gene-disease validity (ClinGen)
Lynch syndrome · ADDefinitivesufficient evidence for diagnostic panels3 gene-disease associations curated in total
Interpreting a novel variant
Loss of function is the curated mechanism (Gene2Phenotype), though the gene is not strongly LoF-constrained in the population — weigh truncating variants against that tolerance.Curated gene-level mechanism — a prior for triage, not a per-variant call.
12
Active trials
564
Pubs (1 yr)
P/LP submissions
P/LP missense
0.57
LOEUF
LOF
Mechanism· G2P
📖
GeneReview available — MLH1
Authoritative clinical overview · Recommended first read
Open GeneReview ↗

Population Genetics & Constraint

gnomAD v4 — loss-of-function & missense intolerance

Moderate LoF intolerance
LoF Constraint?
0.57LOEUF
pLI 0.000
Z-score 3.68
OE 0.37 (0.250.57)
Moderately constrained

More LoF-intolerant than ~75% of genes

Missense Constraint?
-0.30Z-score
OE missense 1.04 (0.961.13)
413 obs / 396.0 exp
Tolerant

Tolerant to missense variation

Observed / Expected Ratios?
LoF OE?0.37 (0.250.57)
00.351.4
Missense OE?1.04 (0.961.13)
00.61.4
Synonymous OE?1.09
01.21.6
LoF obs/exp: 15 / 40.2Missense obs/exp: 413 / 396.0Syn Z: -0.83

ClinVar Variant Classifications

0 submitted variants in ClinVar

Protein Context — Lollipop Plot

MLH1 · protein map & ClinVar variants

Showing all ClinVar variants across the protein. Search a specific variant to highlight its position.

Clinical Trials

Active and recruiting trials from ClinicalTrials.gov

Lymphoma, Non-HodgkinMultiple MyelomaAdvanced Solid Tumors

TAPUR: Testing the Use of Food and Drug Administration (FDA) Approved Drugs That Target a Specific Abnormality in a Tumor Gene in People With Advanced Stage Cancer

RECRUITING
NCT02693535Phase PHASE2American Society of Clinical OncologyStarted 2016-03-14
SunitinibTemsirolimusTrastuzumab and Pertuzumab
Prostate CancerBRCA MutationMismatch Repair Gene Mutation

The IMPACT Study - Identification of Men With a Genetic Predisposition to ProstAte Cancer

ACTIVE NOT RECRUITING
NCT00261456Institute of Cancer Research, United KingdomStarted 2005-03
PSA testProstate Biopsy
Deleterious BARD1 Gene MutationDeleterious BRCA1 Gene MutationDeleterious BRCA2 Gene Mutation

Surgery in Preventing Ovarian Cancer in Patients With Genetic Mutations

ACTIVE NOT RECRUITING
NCT02760849Phase NAM.D. Anderson Cancer CenterStarted 2016-05-02
Laboratory Biomarker AnalysisOophorectomyQuality-of-Life Assessment
Lynch Syndrome

Lynch Syndrome Integrative Epidemiology and Genetics

RECRUITING
NCT06582914University of Colorado, DenverStarted 2024-10-01
Gastrectomy for Gastric CancerGastrectomyMLH1 Gene Mutation

How Epigenetic Changes in hMLH1 Connect Lab Research With Diagnosis in Gastric Cancer

ACTIVE NOT RECRUITING
NCT06982768Fondazione Policlinico Universitario Agostino Gemelli IRCCSStarted 2024-09-01
Colorectal CancerAdenoma ColonAdenoma Colon Polyp

Liquid Biopsy and Machine Learning for Early Colorectal Cancer, Adenomas, Lynch Cancers, and Residual Disease Detection

RECRUITING
NCT07450612San Raffaele UniversityStarted 2024-01-01
BEACON
Lynch SyndromeLynch Syndrome ILynch Syndrome II

Videocapsule Endoscopy in Lynch Syndrome

RECRUITING
NCT05704010Phase NASan Raffaele UniversityStarted 2018-11-01
Video capsule endoscopy
Lynch SyndromeEndometrial Cancer

EC_ItaLynch: Mainstreaming the Diagnosis of Lynch Syndrome

NOT YET RECRUITING
NCT06501417Fondazione Policlinico Universitario Agostino Gemelli IRCCSStarted 2024-08-01
mainstreaming
Endometrial Cancer

Camrelizumab Plus Anlotinib in Patients With Recurrent Sporadic MMRd Endometrial Cancer

NOT YET RECRUITING
NCT05550558Phase PHASE2Sun Yat-Sen Memorial Hospital of Sun Yat-Sen UniversityStarted 2022-11-01
Anlotinib + Camrelizumab
BRCA-Mutated Ovarian CarcinomaBRIP1 Gene MutationMSH2 A636P

Cascade Testing in Families With Newly Diagnosed Hereditary Breast and Ovarian Cancer Syndrome

ACTIVE NOT RECRUITING
NCT04009148NYU Langone HealthStarted 2019-03-01
CASCADE genetic screening
Lynch SyndromeColorectal Cancer (CRC)

Predictive Value of PREMM5, MMRpredict, and Universal Tumor Screening for Lynch Syndrome in Vietnam

NOT YET RECRUITING
NCT06863038University of Medicine and Pharmacy at Ho Chi Minh CityStarted 2025-03-17
Endometrial CancerFertility

Refining Fertility-sparing Treatment in Endometrial Carcinoma Based on Molecular Classification

RECRUITING
NCT07319429Phase PHASE2, PHASE3Fudan UniversityStarted 2026-01-25
PD1 antibodyMedroxyprogesterone Acetate 500 MGMegestrol Acetate 160 MG