10-49619743-G-A

Position:

• chr10-49619743-G-A

Variant summary

Our verdict is Pathogenic. Variant got 12 ACMG points: 12P and 0B. PM2 PP3_Moderate PP5_Very_Strong

The NM_020549.5(CHAT):​c.406G>A​(p.Val136Met) variant causes a missense change. The variant allele was found at a frequency of 0.00008 in 1,612,480 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency:
  • Genomes: 𝑓 0.000099 (0 hom., cov: 32)
  • Exomes 𝑓: 0.000078 (0 hom.)
• Consequence: CHAT NM_020549.5 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:6 U:1
• Conservation: PhyloP100: 4.61

Genes affected

CHAT (HGNC:1912): (choline O-acetyltransferase) This gene encodes an enzyme which catalyzes the biosynthesis of the neurotransmitter acetylcholine. This gene product is a characteristic feature of cholinergic neurons, and changes in these neurons may explain some of the symptoms of Alzheimer's disease. Polymorphisms in this gene have been associated with Alzheimer's disease and mild cognitive impairment. Mutations in this gene are associated with congenital myasthenic syndrome associated with episodic apnea. Multiple transcript variants encoding different isoforms have been found for this gene, and some of these variants have been shown to encode more than one isoform. [provided by RefSeq, May 2010]

CHAT (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 12 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.863
• PP5: Variant 10-49619743-G-A is Pathogenic according to our data. Variant chr10-49619743-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 279754.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr10-49619743-G-A is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
CHAT	NM_020549.5	c.406G>A	p.Val136Met	missense_variant	3/15	ENST00000337653.7	NP_065574.4

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
CHAT	ENST00000337653.7	c.406G>A	p.Val136Met	missense_variant	3/15	1	NM_020549.5	ENSP00000337103.2

Frequencies

GnomAD3 genomes AF: 0.0000986 AC: 15 AN: 152166 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000965

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.000131

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.000132

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.0000400 AC: 10 AN: 249972 Hom.: 0 AF XY: 0.0000222 AC XY: 3 AN XY: 135274

Gnomad AFR exome AF: 0.000124

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000618

Gnomad OTH exome AF: 0.000163

GnomAD4 exome AF: 0.0000781 AC: 114 AN: 1460314 Hom.: 0 Cov.: 32 AF XY: 0.0000743 AC XY: 54 AN XY: 726490

Gnomad4 AFR exome AF: 0.0000598

Gnomad4 AMR exome AF: 0.0000447

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.0000116

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000890

Gnomad4 OTH exome AF: 0.000166

GnomAD4 genome AF: 0.0000986 AC: 15 AN: 152166 Hom.: 0 Cov.: 32 AF XY: 0.0000269 AC XY: 2 AN XY: 74336

Gnomad4 AFR AF: 0.0000965

Gnomad4 AMR AF: 0.000131

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.000132

Gnomad4 OTH AF: 0.00

Alfa AF: 0.000122 Hom.: 0

Bravo AF: 0.0000680

ESP6500AA AF: 0.00 AC: 0

ESP6500EA AF: 0.000233 AC: 2

ExAC AF: 0.0000412 AC: 5

EpiCase AF: 0.00

EpiControl AF: 0.0000593

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:6 Uncertain:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Familial infantile myasthenia Pathogenic:3

Likely pathogenic, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Jul 19, 2023	- -
Pathogenic, criteria provided, single submitter	clinical testing	Baylor Genetics	Mar 20, 2024	- -
Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Nov 05, 2023	This sequence change replaces valine, which is neutral and non-polar, with methionine, which is neutral and non-polar, at codon 136 of the CHAT protein (p.Val136Met). This variant is present in population databases (rs201479289, gnomAD 0.02%). This missense change has been observed in individual(s) with congenital myasthenic syndrome (PMID: 21786365, 26080897, 28497657; Invitae). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. ClinVar contains an entry for this variant (Variation ID: 279754). 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) has been performed at Invitae for this missense variant, however the output from this modeling did not meet the statistical confidence thresholds required to predict the impact of this variant on CHAT protein function. Experimental studies have shown that this missense change affects CHAT function (PMID: 21786365, 26080897). For these reasons, this variant has been classified as Pathogenic. -

Congenital myasthenic syndrome Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Jan 24, 2023	Variant summary: CHAT c.406G>A (p.Val136Met) results in a conservative amino acid change located in the Choline/carnitine acyltransferase domain (IPR039551) of the encoded protein sequence. Three of four in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 4e-05 in 250372 control chromosomes (gnomAD and publication data). This frequency is not significantly higher than expected for a pathogenic variant in CHAT causing Congenital Myasthenic Syndrome (4e-05 vs 0.00079), allowing no conclusion about variant significance. c.406G>A has been reported in the literature in multiple individuals affected with Congenital Myasthenic Syndrome, including at least one homozygote (Shen_2011, Abicht_2012, Arredondo_2015). These data indicate that the variant is very likely to be associated with disease. Functional studies report this variant results in reducing protein expression level and catalytic efficiency of the enzyme (Shen_2011, Arredondo_2015). Five ClinVar submitters (evaluation after 2014) cite this variant as pathogenic (n=2), likely pathogenic (n=2) and uncertain significance (n=1). Based on the evidence outlined above, the variant was classified as pathogenic. -
Likely pathogenic, criteria provided, single submitter	clinical testing	Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine	May 10, 2016	The p.Val54Met variant in CHAT has been reported in four patients with congenita l myasthenic syndrome with episodic apnea (three compound heterozygotes and one homozygote) (Shen 2011, Arredondo 2015). This variant has also been identified i n 5/118276 of chromosomes by the Exome Aggregation Consortium (ExAC, http://exac .broadinstitute.org; dbSNP rs201479289). Although this variant has been seen in the general population, its frequency is low enough to be consistent with a rece ssive carrier frequency. In vitro functional studies provide some evidence that the p.Val54Met variant may impact protein function (Shen 2011, Arredondo 2015). However, these types of assays may not accurately represent biological function. In summary, although additional studies are required to fully establish its cli nical significance, the p.Val54Met variant is likely pathogenic. -

not provided Pathogenic:1 Uncertain:1

Uncertain significance, flagged submission	clinical testing	Eurofins Ntd Llc (ga)	Dec 21, 2015	- -
Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Apr 26, 2022	Published functional studies demonstrate decreased protein expression, as well as reduced catalytic efficiency of the enzyme (Shen et al., 2011; Arredondo et al., 2015); In silico analysis supports that this missense variant does not alter protein structure/function; This variant is associated with the following publications: (PMID: 28497657, 29783273, 31192527, 31980526, 21786365, 26080897, 29759072, 30609409, 34426522, 34557490, 30458023) -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.54
BayesDel_addAF	Pathogenic	0.25	D
BayesDel_noAF	Pathogenic	0.36
CADD	Pathogenic	26
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.81	.;.;.;D;.
Eigen	Pathogenic	0.70
Eigen_PC	Uncertain	0.56
FATHMM_MKL	Uncertain	0.82	D
LIST_S2	Pathogenic	0.97	.;.;D;D;D
M_CAP	Uncertain	0.15	D
MetaRNN	Pathogenic	0.86	D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.8	.;.;.;H;.
PrimateAI	Uncertain	0.51	T
PROVEAN	Uncertain	-2.4	N;N;N;N;N
REVEL	Pathogenic	0.80
Sift	Uncertain	0.0010	D;D;D;D;D
Sift4G	Uncertain	0.0030	D;D;D;D;D
Polyphen		1.0	.;.;.;D;.
Vest4		0.63
MVP		0.95
MPC		0.89
ClinPred		0.95	D
GERP RS		5.1
Varity_R		0.73
gMVP		0.45

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		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: rs201479289; hg19: chr10-50827789; COSMIC: COSV60320179;