chrX-25013229-C-T

Position:

• chrX-25013229-C-T

Variant summary

Our verdict is Uncertain significance. Variant got 0 ACMG points: 2P and 2B. PM2 BP4_Moderate

The NM_139058.3(ARX):​c.766G>A​(p.Ala256Thr) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000956 in 1,045,734 control chromosomes in the GnomAD database, with no homozygous occurrence. There are no hemizygote samples in GnomAD. In-silico tool predicts a benign outcome for this variant. 12/20 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A256D) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 23)
  • Exomes 𝑓: 9.6e-7 (0 hom. 0 hem.)
• Consequence: ARX NM_139058.3 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 0.130

Genes affected

ARX (HGNC:18060): (aristaless related homeobox) This gene is a homeobox-containing gene expressed during development. The expressed protein contains two conserved domains, a C-peptide (or aristaless domain) and the prd-like class homeobox domain. It is a member of the group-II aristaless-related protein family whose members are expressed primarily in the central and/or peripheral nervous system. This gene is thought to be involved in CNS development. Expansion of a polyalanine tract and other mutations in this gene cause X-linked cognitive disability and epilepsy. [provided by RefSeq, Jul 2016]

ACMG classification

Verdict is Uncertain_significance. Variant got 0 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.14411128).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
ARX	NM_139058.3	c.766G>A	p.Ala256Thr	missense_variant	2/5	ENST00000379044.5

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
ARX	ENST00000379044.5	c.766G>A	p.Ala256Thr	missense_variant	2/5	1	NM_139058.3	P1

Frequencies

GnomAD3 genomes Cov.: 23

GnomAD4 exome AF: 9.56e-7 AC: 1 AN: 1045734 Hom.: 0 Cov.: 30 AF XY: 0.00 AC XY: 0 AN XY: 335702

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000122

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 23

Bravo AF: 0.0000151

ExAC AF: 0.00000938 AC: 1

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Intellectual disability, X-linked, with or without seizures, arx-related;C3463992:Developmental and epileptic encephalopathy, 1 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jan 05, 2024

This sequence change replaces alanine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 256 of the ARX protein (p.Ala256Thr). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with ARX-related conditions. ClinVar contains an entry for this variant (Variation ID: 1497051). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is not expected to disrupt ARX protein function with a negative predictive value of 80%. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.10
BayesDel_addAF	Benign	-0.20	T
BayesDel_noAF	Benign	-0.52
CADD	Benign	11
DANN	Uncertain	0.97
DEOGEN2	Benign	0.15	T
FATHMM_MKL	Benign	0.074	N
LIST_S2	Benign	0.46	T
M_CAP	Pathogenic	0.47	D
MetaRNN	Benign	0.14	T
MetaSVM	Benign	-0.64	T
MutationAssessor	Benign	0.55	N
MutationTaster	Benign	1.0	N
PrimateAI	Pathogenic	0.91	D
PROVEAN	Benign	-0.13	N
REVEL	Benign	0.060
Sift	Uncertain	0.022	D
Sift4G	Benign	0.68	T
Polyphen		0.18	B
Vest4		0.10
MutPred		0.34		Gain of phosphorylation at A256 (P = 0.0146);
MVP		0.74
MPC		1.2
ClinPred		0.060	T
GERP RS		3.0
Varity_R		0.070
gMVP		0.17

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs769056463; hg19: chrX-25031346;