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Intellectual disability

Gene: NARS

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NARS (asparaginyl-tRNA synthetase)
EnsemblGeneIds (GRCh38): ENSG00000134440
EnsemblGeneIds (GRCh37): ENSG00000134440
OMIM: 108410, Gene2Phenotype
NARS is in 2 panels

1 review

Konstantinos Varvagiannis (Other)

Green List (high evidence)

[Please note that HGNC Approved Gene Symbol for this gene is NARS1]

Manole et al (2020 - PMID: 32738225) provide evidence that both biallelic and monoallelic (de novo) pathogenic NARS1 variants cause a neurodevelopmental disorder. In total 32 individuals from 21 families are reported, with biallelic variants identified in individuals from 13 families and de novo in 8 families.

Similar features were reported for AR/AD occurrences of the disorder and included microcephaly (90% - most often primary), epilepsy (23/32 or 74% - variable semiology incl. partial/myoclonic/generalized tonic-clonic seizures), DD and ID (as a universal feature), abnormal tone in several (hypotonia/spasticity), ataxia, demyelinating peripheral neuropathy (in 3 or more for each inheritance mode - or a total of 25%). Some individuals had dysmorphic features.

NARS1 encodes an aminoacyl-tRNA synthetase (ARS) [asparaginyl-tRNA synthetase 1]. Aminoacyl-tRNA synthetases constitute a family of enzymes catalyzing attachment of amino-acids to their cognate tRNAs. As the authors comment, mutations in genes encoding several other ARSs result in neurological disorders ranging from peripheral neuropathy to severe multi-systemic NDD. Dominant, recessive or both modes for inheritance for mutations in the same gene (e.g. AARS1, YARS1, MARS1, etc) have been reported.

Some variants were recurrent, e.g. the c.1600C>T / p.Arg534* which occurred in 6 families as a de novo event or c.1633C>T p.Arg545Cys (homozygous in 6 families). 3 different variants were reported to have occured de novo (c.965G>T - p.Arg322Leu, c.1525G>A - p.Gly509Ser, p.Arg534*) with several other variants identified in hmz/compound htz individuals. A single SNV (c.1067A>C - p.Asp356Ala) was suggested to be acting as modifier and pathogenic only when in trans with a severe variant. [NM_004539.4 used as RefSeq for all].

The authors provide several lines of evidence for a partial loss-of-function effect (e.g. reduction in mRNA expression, enzyme levels and activity in fibroblasts or iNPCs) underlying pathogenicity of the variants identified in individuals with biallelic variants. A gain-of-function (dominant-negative) effect is proposed for de novo variants (such effect also demonstrated for the p.Arg534* in a zebrafish model).

As also Manole et al suggest, NARS1 can be considered for inclusion in gene panels for DD/ID, epilepsy and/or demyelinating neuropathy.
Sources: Literature
Created: 2 Aug 2020, 2:03 p.m. | Last Modified: 2 Aug 2020, 2:11 p.m.
Panel Version: 3.219

Mode of inheritance
BOTH monoallelic and biallelic, autosomal or pseudoautosomal

Phenotypes
Abnormal muscle tone; Microcephaly; Global developmental delay; Intellectual disability; Seizures; Ataxia; Abnormality of the face; Demyelinating peripheral neuropathy

Publications

Details

Mode of Inheritance
BOTH monoallelic and biallelic, autosomal or pseudoautosomal
Sources
Phenotypes
  • Abnormal muscle tone
  • Microcephaly
  • Global developmental delay
  • Intellectual disability
  • Seizures
  • Ataxia
  • Abnormality of the face
  • Demyelinating peripheral neuropathy
OMIM
108410
Clinvar variants
Variants in NARS
Penetrance
Complete
Publications
Panels with this gene

History Filter Activity

2 Aug 2020, Gel status: 0

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

Konstantinos Varvagiannis (Other)

gene: NARS was added gene: NARS was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: NARS was set to BOTH monoallelic and biallelic, autosomal or pseudoautosomal Publications for gene: NARS were set to 32738225 Phenotypes for gene: NARS were set to Abnormal muscle tone; Microcephaly; Global developmental delay; Intellectual disability; Seizures; Ataxia; Abnormality of the face; Demyelinating peripheral neuropathy Penetrance for gene: NARS were set to Complete Review for gene: NARS was set to GREEN