Intellectual disabilityGene: SMG8 Amber List (moderate evidence)
Green List (high evidence)
Comment on list classification: Additional cases reported in recent publication (PMID: 33242396) extend the total to at least 5 unrelated families with GDD/ID and different homozygous variants in the SMG8 gene. Also some supporting functional data provided.
Upgraded from Red to Amber, but there is sufficient evidence to promote to Green at the next GMS panel update (added 'for-review' tag)
Created: 23 Dec 2020, 4:52 p.m. | Last Modified: 23 Dec 2020, 4:52 p.m.
Panel Version: 3.683
PMID: 33242396 (2020) - 9 affected individuals from 4 consanguineous families with different biallelic variants in the SMG8 gene. Clinical features include GDD (8/8), dysmorphic features (9/9) microcephaly (6/9), short stature (4/9), brain imaging anomalies (4/5), congenital heart disease (3/9) and cataract (3/8). Only two sibs from Family 2 had a formal ID diagnosis, but this can be inferred from the clinical reports of the other cases demonstrating severe language delays, difficulties to follow simple instructions or perform daily activities.
Several features described here overlap with those in the previously reported cases from PMID: 31130284 (e.g. microcephaly, ID, cataract, VSD)
Created: 23 Dec 2020, 4:44 p.m. | Last Modified: 23 Dec 2020, 4:44 p.m.
Panel Version: 3.681
Comment on list classification: Rating Red as gene only distinguished due to multiple hits in same candidate gene; however, patients display discordant phenotype and ID only reported in one patient.
Created: 27 Aug 2020, 2:56 p.m. | Last Modified: 27 Aug 2020, 2:56 p.m.
Panel Version: 3.271
PMID: 31130284 (2019) - Two individuals with homozygous variants in this gene identified as part of a large candidate gene discovery study. Phenotype in one patient included microcephaly, ID, cataract, and neck hyperpigmentation; while the other presented short stature, microcephaly, fine motor delay, ventricular septal defect, failure to thrive, and facial dysmorphism.
Created: 27 Aug 2020, 2:51 p.m. | Last Modified: 27 Aug 2020, 2:51 p.m.
Panel Version: 3.270
Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal
Green List (high evidence)
Four more families reported in PMID 33242396. Some functional data also provided.
Created: 9 Dec 2020, 7:57 a.m. | Last Modified: 9 Dec 2020, 7:57 a.m.
Panel Version: 3.644
Two unrelated families, no functional data.
Sources: Expert list
Created: 27 Feb 2020, 3:11 a.m.
Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal
Tag for-review tag was added to gene: SMG8.
Phenotypes for gene: SMG8 were changed from Intellectual disability; Microcephaly; Short stature; Facial dysmorphism Edit to Intellectual disability; Microcephaly; Short stature; Facial dysmorphism
Phenotypes for gene: SMG8 were changed from Intellectual disability to Intellectual disability; Microcephaly; Short stature; Facial dysmorphism Edit
Gene: smg8 has been classified as Amber List (Moderate Evidence).
Publications for gene: SMG8 were set to 31130284
Gene: smg8 has been classified as Red List (Low Evidence).
gene: SMG8 was added gene: SMG8 was added to Intellectual disability. Sources: Expert list Mode of inheritance for gene: SMG8 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: SMG8 were set to 31130284 Phenotypes for gene: SMG8 were set to Intellectual disability Review for gene: SMG8 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).
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.
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.