Intellectual disability - microarray and sequencing
Gene: CTNNA2 Green List (high evidence)Comment on list classification: New gene added by external expert and reviewed by curation team: appropriate phenotype, sufficient cases and external expert review all support gene-disease association and relevance to this panel to rate gene to Green.Created: 25 Feb 2019, 4:57 p.m.
from Schaffer et al. (2018) PMID:(PMID: 30013181 reported 13 children from 3 unrelated consanguineous Middle Eastern families with CDCBM9. The patients presented at birth or in early infancy with profoundly delayed global development, hypotonia, and intractable seizures. Brain imaging showed pachygyria with dramatic cortical thickening up to 3 to 4 cm without an obvious posterior-anterior gradient or focal dysplasia.Created: 25 Feb 2019, 4:56 p.m.
I don't know
Biallelic loss-of-function mutations in CTNNA2 cause cortical dysplasia, complex, with other brain malformations 9 (MIM 618174).
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Schaffer et al. (PMID: 30013181) report on 7 individuals from 3 unrelated consanguineous families. All individuals presented with profoundly impaired motor and cognitive development (severe ID in 6/7 for whom this information was available, all 6 from 2 families - a further individual from the 3rd family was non-ambulatory with absent speech at the age of 28 months), with acquired microcephaly and intractable seizures (7/7 - onset: 6m-3y - atonic/myoclonic/infantile spasms). Pachygyria without posterior-anterior gradient or focal dysplasias was common to all.
All affected individuals were homozygous for nonsense mutations, private to each family (3 different variants).
CTNNA2 encodes αN-catenin. It is expressed in human fetal brain, mainly in regions expressing migration markers DCX and TUJ1. Reduced migration was shown for iPSC-derived neural progenitor cells from an affected individual, compared to controls. The protein contains a putative actin-binding domain (ABD) at its C terminus. Several lines of evidence are provided that this domain is critical for the process of neuronal migration.
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CTNNA2 is included in the DD panel of G2P associated with disordered cortical neuronal migration (Disease confidence: probable / ID and seizures among the phenotypes assigned to this entry).
This gene is not commonly included in gene panels for intellectual disability.
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As a result CTNNA2 could be considered for inclusion in this panel as amber or possibly green.
Sources: LiteratureCreated: 26 Dec 2018, 9:56 p.m.
Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal
Phenotypes
Cortical dysplasia, complex, with other brain malformations 9 (MIM 618174)
Publications
Phenotypes for gene: CTNNA2 were changed from Cortical dysplasia, complex, with other brain malformations 9, 618174; intellectual disability; global developmental delay to Cortical dysplasia, complex, with other brain malformations 9, OMIM:618174
Gene: ctnna2 has been classified as Green List (High Evidence).
Phenotypes for gene: CTNNA2 were changed from Cortical dysplasia, complex, with other brain malformations 9, 618174 to Cortical dysplasia, complex, with other brain malformations 9, 618174; intellectual disability; global developmental delay
Phenotypes for gene: CTNNA2 were changed from Cortical dysplasia, complex, with other brain malformations 9 (MIM 618174) to Cortical dysplasia, complex, with other brain malformations 9, 618174
gene: CTNNA2 was added gene: CTNNA2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CTNNA2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: CTNNA2 were set to 30013181 Phenotypes for gene: CTNNA2 were set to Cortical dysplasia, complex, with other brain malformations 9 (MIM 618174) Penetrance for gene: CTNNA2 were set to Complete Review for gene: CTNNA2 was set to AMBER
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 [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.
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.