Intellectual disability syndromic and non-syndromic
Gene: TNRC6B Green List (high evidence)Green List (high evidence)
Granadillo et al (2020 - PMID: 32152250) report on 17 unrelated individuals with heterozygous TNRC6B variants.
Features included hypotonia (10/17), DD/ID (17/17 - ID was not universal: average IQ of 12 individuals was 73 (range : 50-113) with 4 having below 70), ADHD (11/17), ASD or autistic traits (8/17 and 5/17). Some/few presented with abnormal OFC (micro- / macrocephaly in 3/17 and 2/17), abnormal vision or hearing, variable other congenital anomalies, echocardiographic, GI or renal abnormalities, etc. Epilepsy was reported in 1/17. There was no recognisable gestalt.
Variable initial genetic tests (incl. karyotype, CMA, FMR1, sequencing of other genes) were normal in most individuals with 6/17 having additional variants, in (only) 2 cases contributing to the patient's phenotype.
Detected variants were identified following exome (14/17), targeted panel sequencing (2/17) or CMA (1/17) and included 14 pLoF, 1 missense SNV and 2 intragenic deletions.
Variants had occurred as de novo events in 10/13 subjects for whom testing of both parents was possible. 3/13 subjects had inherited the variant from a parent with milder phenotype.
The protein encoded by TNRC6B (similar to TNRC6A, C) is involved in translational inhibition, through association with the Argonaute (Ago) family of proteins which are effectors of post-transcriptional gene silencing.
There were no variant studies performed.
Based on the type of variants identified, the pLI score of 1 in gnomAD and the HI index of 5.61%, the authors suggest haploinsufficiency as the most likely mechanism.
Animal models are not discussed (/possibly not available).
Individuals with de novo TNRC6B variants have also been reported in larger cohorts (e.g. DDD study - PMID: 28135719, Iossifov et al - PMID: 25363768, Lelieveld et al - PMID: 27479843, Jónsson et al - PMID: 28959963).
A previous study provided details on 2 sibs harboring a translocation which disrupted both TNRC6B and TCF20 (also associated with ID)(Babbs et al - PMID: 25228304).
Overall this gene can be upgraded to amber (ID is a feature although mild and not universal) or green rating (DD in all, >=4 subjects with ID and relevant variants). Please consider inclusion/upgrade in other relevant panels such as ASD.Created: 6 May 2020, 3:35 p.m. | Last Modified: 6 May 2020, 3:35 p.m.
Panel Version: 0.2619
Mode of inheritance
MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown
Phenotypes
Global developmental delay; Intellectual disability; Autistic behavior
Publications
Green List (high evidence)
No evidence currently for Mendelian disease association.Created: 20 Nov 2019, 7:29 p.m. | Last Modified: 20 Nov 2019, 7:29 p.m.
Panel Version: 0.13
Mode of inheritance
MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
Phenotypes
Global developmental delay with speech and behavioural abnormalities, MIM# 619243
Phenotypes for gene: TNRC6B were changed from Global developmental delay; Intellectual disability; Autistic behavior to Global developmental delay with speech and behavioural abnormalities, MIM# 619243
Phenotypes for gene: TNRC6B were changed from to Global developmental delay; Intellectual disability; Autistic behavior
Publications for gene: TNRC6B were set to
Mode of inheritance for gene: TNRC6B was changed from Unknown to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
Gene: tnrc6b has been classified as Green List (High Evidence).
Gene: tnrc6b has been classified as Red List (Low Evidence).
Gene: tnrc6b has been classified as Red List (Low Evidence).
gene: TNRC6B was added gene: TNRC6B was added to Intellectual disability, syndromic and non-syndromic_GHQ. Sources: Expert Review Green,Genetic Health Queensland Mode of inheritance for gene: TNRC6B 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.