Intellectual disability - microarray and sequencing
Gene: PLEKHG2 Amber List (moderate evidence)Comment on list classification: PLEKHG2 was added to the ID panel and rated Amber by Konstantinos Varvagiannis based on two papers.
Edvardson et al. (2016 - PMID: 26573021) reported five children from 2 unrelated consanguineous Palestinian families, all with same variant homozygous missense variant, although it was stated the families were unrelated, this could be a founder effect. For one family samples were not available for parents only the grandmothers.
Karaca et al. (2015 - PMID: 26539891) identified an individual homozygous for a PLEKHG2 missense variant (NM_022835.2:c.1708G>A or p.Gly570Arg) who also had an affected sibling. This was a large study with limited clinical information.
As only two variants in consanguineous families have been reported and sample information not available for all parents, adding gene to "watchlist" and conclude that it should be Amber.Created: 29 May 2019, 10:43 a.m. | Last Modified: 17 Jul 2019, 2:21 p.m.
Panel Version: 0.201
I don't know
Karaca et al. (2015 - PMID: 26539891) in a study of 128 - mostly consanguineous - families with neurogenetic disorders and brain malformations, identified an individual homozygous for a PLEKHG2 missense variant (NM_022835.2:c.1708G>A or p.Gly570Arg). This individual (BAB4830) had a similarly affected sib. Features included hypotonia, intellectual disability, microcephaly, cerebellar atrophy and nystagmus (description provided in supplement - Table S1). This variant has been submitted in ClinVar as likely pathogenic by the corresponding laboratory (SCV000537940.1).
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Edvardson et al. (2016 - PMID: 26573021) reported on 5 individuals from 2 unrelated consanguineous Palestinian families, harboring a missense variant in the homozygous state (NM_022835.2:c.610C>T or p.Arg204Trp - 1/5 was unavailable for testing).
Unaffected relatives were either heterozygous for this variant or homozygous for the reference allele.
Common features included hypotonia (5/5), DD/ID (5/5), postnatal microcephaly (5/5), dystonia (3/5), nystagmus (2/5) or seizures (1/5) [many of these similar to those reported by Karaca et al]. Brain MRI images were consistent with leukodystrophy and prolonged relaxation of dorsal tegmental tracts (similar findings were not commented by Karaca et al).
PLEKHG2 encodes a Rho guanine exchange factor (RhoGEF). RhoGEFs activate RhoGTPases through release of GDP and binding of GTP. Mutations in other RhoGEFs have been associated with neurodevelopmental disorders.
PLEKHG2 activity was shown to be significantly decreased in HEK293A cells transfected with R204W-PLEKHG2 when compared to tranfection with wt. Western blotting suggested that this was not the result of defective expression.
Using lymphoblastoid cell lines from peripheral B lymphocytes from individuals homozygous for R204W and controls, similar levels of expression were shown between the 2 groups (upon Western Blot).
As the authors note, PLEKHG2 is required for Rac- and Cdc42-stimulated actin polymerization in leukocytes (PMID cited: 24001768).
SDF1a-stimulated actin polymerization was studied in patient cells and was shown to be significantly impaired. In line with this actin polymerization was also impaired upon siRNA-mediated downregulation of PLEKHG2 expression in control cells.
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A subsequent submission of the Gly570Arg variant in ClinVar (2017 - SCV000609979.1 - same variant as the one reported by Karaca et al) reports this as a VUS.
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PLEKHG2 is associated with Leukodystrophy and acquired microcephaly with or without dystonia (616763) in OMIM.
This gene is not associated with any phenotype in G2P.
PLEKHG2 is included in gene panels for ID offered by some diagnostic laboratories.
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As a result, this gene could be considered for inclusion in this panel probably as amber (or green if the current evidence is considered to be sufficient).
Sources: LiteratureCreated: 22 Jan 2019, 9:05 a.m.
Mode of inheritance
MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown
Phenotypes
Leukodystrophy and acquired microcephaly with or without dystonia, 616763
Publications
Variants in this GENE are reported as part of current diagnostic practice
Tag watchlist tag was added to gene: PLEKHG2.
Source Expert Review was added to PLEKHG2. Source Expert Review Amber was added to PLEKHG2. Added phenotypes Leukodystrophy and acquired microcephaly with or without dystonia, 616763 for gene: PLEKHG2 Publications for gene PLEKHG2 were changed from 26539891; 26573021; 24001768 to 26539891; 24001768; 26573021 Rating Changed from No List (delete) to Amber List (moderate evidence)
gene: PLEKHG2 was added gene: PLEKHG2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PLEKHG2 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: PLEKHG2 were set to 26539891; 26573021; 24001768 Phenotypes for gene: PLEKHG2 were set to Leukodystrophy and acquired microcephaly with or without dystonia, 616763 Penetrance for gene: PLEKHG2 were set to unknown Review for gene: PLEKHG2 was set to AMBER gene: PLEKHG2 was marked as current diagnostic
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.