rs372760913

Variant summary

Our verdict is Pathogenic. Variant got 14 ACMG points: 14P and 0B. PM1PM2PP3_ModeratePP5_Very_Strong

The NM_020549.5(CHAT):c.1669G>A(p.Ala557Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.0000644 in 1,613,868 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 (★★). Synonymous variant affecting the same amino acid position (i.e. A557A) has been classified as Likely benign.

Frequency

Genomes: 𝑓 0.000039 ( 0 hom., cov: 32)

Exomes 𝑓: 0.000067 ( 0 hom. )

Consequence

CHAT
NM_020549.5 missense

Scores

Clinical Significance

Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:5

Conservation

PhyloP100: 10.0

Variant links:

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 links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Pathogenic. Variant got 14 ACMG points.

PM1

In a hotspot region, there are 2 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 2 benign, 4 uncertain in NM_020549.5

PM2

Very rare variant in population databases, with high coverage;

PP3

MetaRNN computational evidence supports a deleterious effect, 0.904

PP5

Variant 10-49655129-G-A is Pathogenic according to our data. Variant chr10-49655129-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 461452.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr10-49655129-G-A is described in Lovd as [Pathogenic]. Variant chr10-49655129-G-A is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
CHAT	NM_020549.5 linkuse as main transcript	c.1669G>A	p.Ala557Thr	missense_variant	12/15	ENST00000337653.7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
CHAT	ENST00000337653.7 linkuse as main transcript	c.1669G>A	p.Ala557Thr	missense_variant	12/15	1	NM_020549.5	P2	P28329-1

Frequencies

GnomAD3 genomes

AF:

0.0000395

AC:

AN:

152050

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.000145

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

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:

0.00

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.0000517

AC:

AN:

251264

Hom.:

AF XY:

0.0000515

AC XY:

AN XY:

135882

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad SAS exome

AF:

0.0000327

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.0000968

Gnomad OTH exome

AF:

0.000163

GnomAD4 exome

AF:

0.0000670

AC:

AN:

1461818

Hom.:

Cov.:

AF XY:

0.0000701

AC XY:

AN XY:

727216

show subpopulations

Gnomad4 AFR exome

AF:

0.00

Gnomad4 AMR exome

AF:

0.00

Gnomad4 ASJ exome

AF:

0.00

Gnomad4 EAS exome

AF:

0.0000252

Gnomad4 SAS exome

AF:

0.0000232

Gnomad4 FIN exome

AF:

0.0000187

Gnomad4 NFE exome

AF:

0.0000827

Gnomad4 OTH exome

AF:

0.0000331

GnomAD4 genome

AF:

0.0000395

AC:

AN:

152050

Hom.:

Cov.:

AF XY:

0.0000269

AC XY:

AN XY:

74246

show subpopulations

Gnomad4 AFR

AF:

0.000145

Gnomad4 AMR

AF:

0.00

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.00

Gnomad4 OTH

AF:

0.00

Alfa

AF:

0.000205

Hom.:

Bravo

AF:

0.0000718

ESP6500AA

AF:

0.00

AC:

ESP6500EA

AF:

0.000116

AC:

ExAC

AF:

0.0000577

AC:

EpiCase

AF:

0.000109

EpiControl

AF:

0.0000593

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:5

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

Familial infantile myasthenia

Pathogenic:3

Likely pathogenic, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Aug 29, 2019	- -
Pathogenic, criteria provided, single submitter	clinical testing	Baylor Genetics	Oct 10, 2023	- -
Pathogenic, criteria provided, single submitter	clinical testing	Invitae	Jan 29, 2024	This sequence change replaces alanine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 557 of the CHAT protein (p.Ala557Thr). This variant is present in population databases (rs372760913, gnomAD 0.009%). This missense change has been observed in individuals with congenital myasthenic syndrome (PMID: 19520274, 29189923; Invitae). ClinVar contains an entry for this variant (Variation ID: 461452). 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 expected to disrupt CHAT protein function with a positive predictive value of 95%. Experimental studies have shown that this missense change affects CHAT function (PMID: 21786365). For these reasons, this variant has been classified as Pathogenic. -

not provided

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Jul 27, 2022

Published functional studies demonstrate a damaging effect, as the A557T variant demonstrates reduced expression, low catalytic rate, and an extremely low affinity for acetyl-CoA and choline in comparison to wild-type (PMID: 21786365); Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; This variant is associated with the following publications: (PMID: 19520274, 21786365, 29189923, 29783273, 26080897, 33650116, Kong 2022 [Poster], 34431804) -

Congenital myasthenic syndrome

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Nov 20, 2023

Variant summary: CHAT c.1669G>A (p.Ala557Thr) results in a non-conservative amino acid change located in the Choline/carnitine acyltransferase domain (IPR039551) of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 5.2e-05 in 251264 control chromosomes (gnomAD). This frequency is not significantly higher than estimated for a pathogenic variant in CHAT causing Congenital Myasthenic Syndrome (5.2e-05 vs 0.00079), allowing no conclusion about variant significance. c.1669G>A has been reported in the literature in multiple individuals affected with Congenital Myasthenic Syndrome (e.g., Mallory_2009, Shen_2011). These data indicate that the variant is very likely to be associated with disease. At least one publication reports experimental evidence evaluating an impact on protein function, finding that the variant results in reduced expression and catalytic efficiency (e.g., Shen_2011). The following publications have been ascertained in the context of this evaluation (PMID: 19520274, 21786365). Three submitters have reported clinical-significance assessments for this variant to ClinVar after 2014. All submitters classified the variant as pathogenic/likely pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Pathogenic

0.71

BayesDel_addAF

Pathogenic

0.35

BayesDel_noAF

Pathogenic

0.47

Cadd

Pathogenic

Dann

Pathogenic

1.0

Eigen

Pathogenic

0.82

Eigen_PC

Pathogenic

0.69

FATHMM_MKL

Pathogenic

0.99

M_CAP

Pathogenic

0.34

MetaRNN

Pathogenic

0.90

D;D;D;D;D;D

MetaSVM

Pathogenic

1.0

MutationTaster

Benign

1.0

D;D;D;D;D;D

PrimateAI

Uncertain

0.65

PROVEAN

Uncertain

-3.8

D;D;D;D;D;.

REVEL

Pathogenic

0.86

Sift

Uncertain

0.0010

D;D;D;D;D;.

Sift4G

Uncertain

0.0030

D;D;D;D;D;.

Polyphen

1.0

.;.;.;D;.;.

Vest4

0.94

MVP

0.97

MPC

0.85

ClinPred

0.85

GERP RS

5.4

Varity_R

0.87

gMVP

0.87

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

Below is the list of publications found by LitVar. It may be empty.

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

LitVar

Other links and lift over