Intellectual disabilityGene: MED12L Amber List (moderate evidence)
Comment on list classification: Rating Amber. CNVs encompass other genes. Two cases with SNVs have moderate/severe ID and one of these also has a VUS in TUBB2B. The other two SNV cases have mild ID.
Created: 19 Jun 2019, 10:40 a.m.
Not associated with any phenotype in OMIM or Gene2Phenotype.
PMID: 31155615 - Nizon et al. 2019 - 7 affected individuals harboring variants involving MED12L identified by array CGH, exome or genome sequencing. All affected individuals presented with intellectual disability and/or developmental delay (3 mild, 3 moderate, 1 severe with seizures). 3 individuals had a MED12L deletion or duplication. All encompass other genes aswell as MED12L. In 2 cases these could be confirmed as de novo. 4 individuals had single-nucleotide variants (one nonsense, one frameshift, and two splicing variants). In two cases these variants were found to have occurred de novo. One individual also had a variant in TUBB2B that was classified as unknown signficance. Functional analysis confirmed a moderate and significant alteration of RNA synthesis in two individuals (Konstantios Varvagiannis notes this data is from individuals with CNVs).
Summary: 7 unrelated cases, 4 different SNVs plus 3 CNVs. Mild ID in 2 of the SNV cases and 1 CNV case. Some segregation and functional data.
Created: 19 Jun 2019, 10:31 a.m.
I don't know
Nizon et al. (2019 - PMID: 31155615) report on 7 unrelated individuals with nucleotide or copy-number variants in MED12L.
Features included motor delay (4/7), speech impairment (7/7) with ID of variable degrees (7/7 - mild to severe). Variable behavioral abnormalities (ASD in 4/7, aggressive behavior, ADHD, etc), functional GI anomalies, corpus callosum abnormalities and seizures were among other features noted in some/few. There was no recognizable facial phenotype.
Nucleotide variants included 1 stopgain, 1 frameshift and 2 splice site variants. 3 CNVs were reported (two 3q25.1 microduplications of 460- and 147-kb respectively and one microdeletion of 291-kb) although all spanned also other genes.
De novo occurrence was shown for 2 CNVs and 2 SNVs, as parental samples were unavailable for 3 of the subjects.
Contribution of other genetic (eg. an inherited 22q11.2 microduplication, VUS in other genes) or environmental factors could not be ruled out for few individuals.
Among the arguments provided:
MED12L encodes a subunit of the kinase module of the mediator complex, a complex required for transcription by RNA polymerase II. Mutations in other subunits of the kinase module (eg. MED12, MED13L, etc) have been implicated in intellectual disability.
The protein is localized in the nucleus. The gene is mainly expressed in the brain.
The functional effect of 2 CNVs was evaluated using the recovery of RNA synthesis assay, an assay reflecting global transcriptional activity. Fibrobast studies from one individual with microdeletion and one further subject with microduplication demonstrated decreased RNA synthesis compared to controls. Decreased RNA synthesis was also observed in cell lines from individuals with mutations in other genes for subunits of the mediator complex (eg. MED12 or MED13L) or from individuals with Cockayne syndrome.
Therefore haploinsufficiency is suggested to underly the transcriptional defect. (MED12L also appears to be intolerant to LoF variation with a pLI score of 1).
Some features appear to be common among the disorders caused by pathogenic variants in MED12L or other subunits of the kinase module (MED12, MED13, MED13L) eg. ID, abnormal behaviour or autistic features.
Animal models are not discussed / (probably not) available (MGI for Med12l : http://www.informatics.jax.org/marker/MGI:2139916).
MED12L is not associated with any phenotype in OMIM or G2P. The gene is not commonly included in gene panels for ID offered by diagnostic laboratories.
As a result, this gene can be considered for inclusion in the ID panel, probably as amber (4 variants affecting only MED12L, segregation studies performed for 2, degree of ID reported mild on 2 occasions) pending further reports.
Created: 8 Jun 2019, 5:33 p.m.
Mode of inheritance
MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown
Motor delay; Delayed speech and language development; Intellectual disability; Behavioral abnormality; Abnormality of the abdomen; Seizures; Abnormality of the corpus callosum
Gene: med12l has been classified as Amber List (Moderate Evidence).
gene: MED12L was added gene: MED12L was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: MED12L was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: MED12L were set to 31155615 Phenotypes for gene: MED12L were set to Motor delay; Delayed speech and language development; Intellectual disability; Behavioral abnormality; Abnormality of the abdomen; Seizures; Abnormality of the corpus callosum Penetrance for gene: MED12L were set to unknown Review for gene: MED12L was set to AMBER
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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).
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).
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.
D. Evidence indicates that disease-causing mutations follow a Mendelian pattern of causation appropriate for reporting in a diagnostic setting(iv).
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 [email protected]
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.
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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.