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Genetic epilepsy syndromes

Gene: RHOBTB2

Green List (high evidence)

RHOBTB2 (Rho related BTB domain containing 2)
EnsemblGeneIds (GRCh38): ENSG00000008853
EnsemblGeneIds (GRCh37): ENSG00000008853
OMIM: 607352, Gene2Phenotype
RHOBTB2 is in 3 panels

4 reviews

Rebecca Foulger (Genomics England curator)

I don't know

Review and rating collated by Tracy Lester (Oxford Medical Genetics Laboratories Oxford University Hospitals NHS Foundation Trust, 2019_02_06) on behalf of Wessex and West Midlands GLH for GMS Neurology specialist test group, for Clinical Indication R59 'Early onset or syndromic epilepsy'. Review contributors: John Taylor and Helen Lord. Suggested gene rating: Green.
Created: 6 Aug 2019, 8:38 p.m. | Last Modified: 6 Aug 2019, 8:38 p.m.
Panel Version: 1.189

Tracy Lester (Genetics laboratory, Oxford UK)

Green List (high evidence)

AD EIEE 64 - onset of seizures in first year of life and is assoc with ID, poor motor development and poor/absent speech. Straub et al, 2018 - 10 unrelated patients aged 2-17 with early onset seizures. 9 had variable seizures in first year of life and 1 had onset of focal seizures age 3. Seizure types variable including focal dyscognitive, complex partial and generalised tonic-clonic seizures. 5 diff de novo het missense mutations identified by trio based exome seq - all mutations aff the first or second BTB domains at positions important for stabilising interactions within the domain or for dimer formation. overexpression studies done for 3 mutations.
Created: 6 Aug 2019, 8:31 p.m. | Last Modified: 6 Aug 2019, 8:31 p.m.
Panel Version: 1.188

Mode of inheritance
MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted

Phenotypes
Epileptic encephalopathy early infantile, 618004

Publications

Sarah Leigh (Genomics England Curator)

Comment when marking as ready: Associated with phenotype in OMIM and not in Gen2Phen. At least 6 variants identified in 8 unrelated cases. In vitro functional studies suggest that pathogenicity results from increased expression or reduced degradation of the variant peptides in affected individuals (PMID 29276004).
Created: 19 Nov 2018, 9:08 a.m.

Konstantinos Varvagiannis (Other)

Green List (high evidence)

PMID: 29276004 reports on 10 unrelated patients with de novo pathogenic missense variants in RHOBTB2. The phenotype in all individuals was compatible with a developmental and epileptic encephalopathy including early-onset seizures, severe intellectual disability, postnatal onset microcephaly (6/10) and movement disorders (8/10).

The variants occured as de novo events and clustered within the BTB-domain encoding region (within and between the 2 BTB domains). Three missense variants were recurrent and/or concerned the same residue (p.Arg483His in 4 individuals, Arg511Gln was reported in 2, and Arg511Trp was was found in another 2 individuals).

Functional studies in HEK293 cells suggested increased abundance of the mutant protein secondary to decreased proteasome degradation. Using Drosophila as a model organism, altered expression of RhoBTB (the single ortholog of the 3 vertebrate paralogs, closest to RHOBTB2) was shown to result in neurological phenotypes. RhoBTB overexpression in particular was associated with increased bang sensitivity (which was not the case or milder in the case if knockdown of this gene) and impaired performance upon the negative geotaxis assay, similar to the human neurological phenotypes. Altered RhoBTB dosage was shown to be associated with impaired dendrite development.

As commented by the authors, these results as well as the clustering of missense variants and the pLI score of 0.51 reported for RHOBTB2 are consistent with altered protein function (due to the missense variants) rather than haploinsufficiency or loss-of-function.

PMID: 29768694 describes 3 additional individuals, all found to harbor de novo missense variants again within the BTB-domain encoding region. Two of the variants had been reported in the previous study (Arg511Gln and Arg483His) while the third was a private one (Arg507Cys). The phenotype was similar to the previous descriptions. Functional studies were suggestive of impaired degradation of the mutant protein by the CUL3 complex although this was not secondary to decreased binding with CUL3.

PMID: 26740508 (cited by the two aforementioned publications) reports briefly on an individual with de novo missense variant in the same region of RHOBTB2 (Asn510Asp) and Rett-like phenotype.

RHOBTB2 is included in gene panels for intellectual disability offered by different diagnostic laboratories.

As a result the gene can be considered for inclusion in the intellectual disability and epilepsy panels as green.
Sources: Expert Review, Literature
Created: 10 Nov 2018, 8:35 p.m.

Mode of inheritance
MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown

Phenotypes
Global developmental delay; Intellectual disability; Seizures; Postnatal microcephaly

Publications

Mode of pathogenicity
Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments

Details

Mode of Inheritance
MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown
Sources
  • Wessex and West Midlands GLH
  • NHS GMS
  • Expert Review Green
Phenotypes
  • Epileptic encephalopathy, early infantile, 64 618004
OMIM
607352
Clinvar variants
Variants in RHOBTB2
Penetrance
unknown
Publications
Mode of Pathogenicity
Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments
Panels with this gene

History Filter Activity

6 Aug 2019, Gel status: 3

Added New Source

Rebecca Foulger (Genomics England curator)

Source Wessex and West Midlands GLH was added to RHOBTB2.

6 Aug 2019, Gel status: 3

Added New Source

Rebecca Foulger (Genomics England curator)

Source NHS GMS was added to RHOBTB2.

11 Dec 2018, Gel status: 3

Panel promoted to version 1.0

Sarah Leigh (Genomics England Curator)

Konstantinos Varvagiannis: PMID: 29276004 reports on 10 u

19 Nov 2018, Gel status: 3

Entity classified by Genomics England curator

Sarah Leigh (Genomics England Curator)

Gene: rhobtb2 has been classified as Green List (High Evidence).

19 Nov 2018, Gel status: 3

Entity classified by Genomics England curator

Sarah Leigh (Genomics England Curator)

Gene: rhobtb2 has been classified as Green List (High Evidence).

19 Nov 2018, Gel status: 0

Set Phenotypes

Sarah Leigh (Genomics England Curator)

Phenotypes for gene: RHOBTB2 were changed from Global developmental delay; Intellectual disability; Seizures; Postnatal microcephaly to Epileptic encephalopathy, early infantile, 64 618004

10 Nov 2018, Gel status: 0

Created, Added New Source, Set mode of inheritance, Set publications, Set Phenotypes, Set penetrance, Set mode of pathogenicity

Konstantinos Varvagiannis (Other)

gene: RHOBTB2 was added gene: RHOBTB2 was added to Genetic Epilepsy Syndromes. Sources: Expert Review,Literature Mode of inheritance for gene: RHOBTB2 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: RHOBTB2 were set to 29276004; 29768694; 26740508 Phenotypes for gene: RHOBTB2 were set to Global developmental delay; Intellectual disability; Seizures; Postnatal microcephaly Penetrance for gene: RHOBTB2 were set to unknown Mode of pathogenicity for gene: RHOBTB2 was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: RHOBTB2 was set to GREEN