Mendeliome
Gene: KCNQ3 Green List (high evidence)Green List (high evidence)
From ClinGen:
Definitive for DOMINANT complex neurodevelopmental disorder MONDO:0100038, KCNQ3-related - 24 probands across 7 publications, mostly de novo variants. Mutations are clustered at p.Arg227 and p.Arg230, with a gain of function mechanism PMID: 24851285.
Moderate for DOMINANT self-limited familial neonatal epilepsy (Seizures, benign neonatal, 2 (MIM#121201)) - 15 missense in 18 probands across 16 publications. Variants clustered in the pore region (S5, S6, and intervening loop) and result in loss of function of channel activity PMID: 24851285. Note- there are several NMD predicted variants in this gene with over 10 hets in gnomad.
Limited for RECESSIVE genetic developmental and epileptic encephalopathy MONDO:0100062, KCNQ3-related - 1 individual and 1 family from 2 publications with homozygous frameshifts PMID: 29852413; 31440727. All have seizures, various brain MRI findings, developmental delay and intellectual disability. The family had 3 similarly affected siblings, all homozygous for an NMD frameshift. The unrelated patient had a mildly affected uncle with learning difficulties and transient neonatal seizures, he was not tested for the variant.
A third recessive patient not reported by ClinGen PMID: 29383681: 7yo girl with seizures, severe neurological impairment, and developmental delay. Compound heterozygous for two missense variants Val359Leu and Asp542Asn. Patch clamp studies showed that expression of either variant alone did not affect current density, but co-expression of both variants lead to a significant current reduction.
borderline amber/green for recessiveCreated: 10 Dec 2025, 11:08 a.m. | Last Modified: 10 Dec 2025, 11:10 a.m.
Panel Version: 1.3762
Mode of inheritance
BOTH monoallelic and biallelic, autosomal or pseudoautosomal
Phenotypes
Complex neurodevelopmental disorder MONDO:0100038, KCNQ3-related; Seizures, benign neonatal, 2 MIM#121201; genetic developmental and epileptic encephalopathy MONDO:0100062, KCNQ3-related
Publications
Green List (high evidence)
Five unrelated families reported.Created: 30 Dec 2020, 8:39 a.m. | Last Modified: 30 Dec 2020, 8:39 a.m.
Panel Version: 0.5866
Mode of inheritance
MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
Phenotypes
Seizures, benign neonatal, 2, MIM# 121201
Publications
Mode of inheritance for gene: KCNQ3 was changed from MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted to BOTH monoallelic and biallelic, autosomal or pseudoautosomal
Publications for gene: KCNQ3 were set to 33337327
Phenotypes for gene: KCNQ3 were changed from Seizures, benign neonatal, 2, MIM# 121201 to Complex neurodevelopmental disorder MONDO:0100038, KCNQ3-related; Seizures, benign neonatal, 2 MIM#121201; genetic developmental and epileptic encephalopathy MONDO:0100062, KCNQ3-related
Gene: kcnq3 has been classified as Green List (High Evidence).
Phenotypes for gene: KCNQ3 were changed from to Seizures, benign neonatal, 2, MIM# 121201
Publications for gene: KCNQ3 were set to
Mode of inheritance for gene: KCNQ3 was changed from Unknown to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
gene: KCNQ3 was added gene: KCNQ3 was added to Mendeliome_VCGS. Sources: Expert Review Green,Victorian Clinical Genetics Services Mode of inheritance for gene: KCNQ3 was set to Unknown
If promoting or demoting a gene, please provide comments to justify a decision to move it.
Genes included in a Genomics England gene panel for a rare disease category (green list) should fit the criteria A-E outlined below.
These guidelines were developed as a combination of the ClinGen DEFINITIVE evidence for a causal role of the gene in the disease(a), and the Developmental Disorder Genotype-Phenotype (DDG2P) CONFIRMED DD Gene evidence level(b) (please see the original references provided below for full details). These help provide a guideline for expert reviewers when assessing whether a gene should be on the green or the red list of a panel.
A. There are plausible disease-causing mutations(i) within, affecting or encompassing an interpretable functional region(ii) of this gene identified in multiple (>3) unrelated cases/families with the phenotype(iii).
OR
B. There are plausible disease-causing mutations(i) within, affecting or encompassing cis-regulatory elements convincingly affecting the expression of a single gene identified in multiple (>3) unrelated cases/families with the phenotype(iii).
OR
C. As definitions A or B but in 2 or 3 unrelated cases/families with the phenotype, with the addition of convincing bioinformatic or functional evidence of causation e.g. known inborn error of metabolism with mutation in orthologous gene which is known to have the relevant deficient enzymatic activity in other species; existence of an animal model which recapitulates the human phenotype.
AND
D. Evidence indicates that disease-causing mutations follow a Mendelian pattern of causation appropriate for reporting in a diagnostic setting(iv).
AND
E. No convincing evidence exists or has emerged that contradicts the role of the gene in the specified phenotype.
(i)Plausible disease-causing mutations: Recurrent de novo mutations convincingly affecting gene function. Rare, fully-penetrant mutations - relevant genotype never, or very rarely, seen in controls. (ii) Interpretable functional region: ORF in protein coding genes miRNA stem or loop. (iii) Phenotype: the rare disease category, as described in the eligibility statement. (iv) Intermediate penetrance genes should not be included.
It’s assumed that loss-of-function variants in this gene can cause the disease/phenotype unless an exception to this rule is known. We would like to collect information regarding exceptions. An example exception is the PCSK9 gene, where loss-of-function variants are not relevant for a hypercholesterolemia phenotype as they are associated with increased LDL-cholesterol uptake via LDLR (PMID: 25911073).
If a curated set of known-pathogenic variants is available for this gene-phenotype, please contact us at panelapp@genomicsengland.co.uk
We classify loss-of-function variants as those with the following Sequence Ontology (SO) terms:
Term descriptions can be found on the PanelApp homepage and Ensembl.
If you are submitting this evaluation on behalf of a clinical laboratory please indicate whether you report variants in this gene as part of your current diagnostic practice by checking the box
Standardised terms were used to represent the gene-disease mode of inheritance, and were mapped to commonly used terms from the different sources. Below each of the terms is described, along with the equivalent commonly-used terms.
A variant on one allele of this gene can cause the disease, and imprinting has not been implicated.
A variant on the paternally-inherited allele of this gene can cause the disease, if the alternate allele is imprinted (function muted).
A variant on the maternally-inherited allele of this gene can cause the disease, if the alternate allele is imprinted (function muted).
A variant on one allele of this gene can cause the disease. This is the default used for autosomal dominant mode of inheritance where no knowledge of the imprinting status of the gene required to cause the disease is known. Mapped to the following commonly used terms from different sources: autosomal dominant, dominant, AD, DOMINANT.
A variant on both alleles of this gene is required to cause the disease. Mapped to the following commonly used terms from different sources: autosomal recessive, recessive, AR, RECESSIVE.
The disease can be caused by a variant on one or both alleles of this gene. Mapped to the following commonly used terms from different sources: autosomal recessive or autosomal dominant, recessive or dominant, AR/AD, AD/AR, DOMINANT/RECESSIVE, RECESSIVE/DOMINANT.
A variant on one allele of this gene can cause the disease, however a variant on both alleles of this gene can result in a more severe form of the disease/phenotype.
A variant in this gene can cause the disease in males as they have one X-chromosome allele, whereas a variant on both X-chromosome alleles is required to cause the disease in females. Mapped to the following commonly used term from different sources: X-linked recessive.
A variant in this gene can cause the disease in males as they have one X-chromosome allele. A variant on one allele of this gene may also cause the disease in females, though the disease/phenotype may be less severe and may have a later-onset than is seen in males. X-linked inactivation and mosaicism in different tissues complicate whether a female presents with the disease, and can change over their lifetime. This term is the default setting used for X-linked genes, where it is not known definitately whether females require a variant on each allele of this gene in order to be affected. Mapped to the following commonly used terms from different sources: X-linked dominant, x-linked, X-LINKED, X-linked.
The gene is in the mitochondrial genome and variants within this can cause this disease, maternally inherited. Mapped to the following commonly used term from different sources: Mitochondrial.
Mapped to the following commonly used terms from different sources: Unknown, NA, information not provided.
For example, if the mode of inheritance is digenic, please indicate this in the comments and which other gene is involved.