Genetic Variant NM_020549.5:c.745C>A (chr10-49622143-C-A) – ACMG Classification: Uncertain_significance (2 pts)

Variant summary

Our verdict is Uncertain significance. The variant received 2 ACMG points: 2P and 0B. PM2

The NM_020549.5(CHAT):c.745C>A(p.Leu249Met) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000704 in 1,419,788 control chromosomes in the GnomAD database, with no homozygous occurrence. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. L249V) has been classified as Likely benign.

Frequency

Genomes: not found (cov: 32)

Exomes 𝑓: 7.0e-7 ( 0 hom. )

Consequence

CHAT
NM_020549.5 missense

Scores

Clinical Significance

Not reported in ClinVar

Conservation

PhyloP100: 1.08

Publications

0 publications found

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 Gene-Disease associations (from GenCC):

congenital myasthenic syndrome 6
Inheritance: AR Classification: STRONG Submitted by: PanelApp Australia, Labcorp Genetics (formerly Invitae), Genomics England PanelApp
presynaptic congenital myasthenic syndrome
Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

CHAT links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Uncertain_significance. The variant received 2 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
CHAT	NM_020549.5 link	c.745C>A	p.Leu249Met	missense_variant	Exon 5 of 15	ENST00000337653.7	NP_065574.4	P28329-1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
CHAT	ENST00000337653.7 link	c.745C>A	p.Leu249Met	missense_variant	Exon 5 of 15	1	NM_020549.5	ENSP00000337103.2		P28329-1

Frequencies

GnomAD3 genomes

Cov.:

GnomAD4 exome

AF:

7.04e-7

AC:

AN:

1419788

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

705994

show subpopulations

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR)

AF:

0.00

AC:

AN:

32164

American (AMR)

AF:

0.00

AC:

AN:

43376

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

24352

East Asian (EAS)

AF:

0.00

AC:

AN:

36544

South Asian (SAS)

AF:

0.00

AC:

AN:

85850

European-Finnish (FIN)

AF:

0.00

AC:

AN:

49782

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5506

European-Non Finnish (NFE)

AF:

9.22e-7

AC:

AN:

1084738

Other (OTH)

AF:

0.00

AC:

AN:

57476

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.375

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

GnomAD4 genome

Cov.:

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.25

BayesDel_addAF

Uncertain

0.12

BayesDel_noAF

Uncertain

-0.060

CADD

Uncertain

(source)

DANN

Uncertain

1.0

DEOGEN2

Uncertain

0.57

.;.;.;D;.

Eigen

Uncertain

0.44

Eigen_PC

Uncertain

0.43

FATHMM_MKL

Uncertain

0.79

LIST_S2

Benign

0.78

.;.;T;T;T

M_CAP

Uncertain

0.15

MetaRNN

Uncertain

0.61

D;D;D;D;D

MetaSVM

Pathogenic

0.84

MutationAssessor

Pathogenic

3.5

.;.;.;H;.

PhyloP100

1.1

PrimateAI

Benign

0.47

PROVEAN

Benign

-1.4

N;N;N;N;N

REVEL

Pathogenic

0.69

Sift

Uncertain

0.0060

D;D;D;D;D

Sift4G

Uncertain

0.015

D;D;D;D;D

Polyphen

0.91

.;.;.;P;.

Vest4

0.45

MutPred

0.76

.;.;.;Gain of helix (P = 0.132);.;

MVP

0.95

MPC

0.87

ClinPred

0.98

GERP RS

4.8

Varity_R

0.57

gMVP

0.44

Mutation Taster

=89/11

polymorphism

(source)

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.010

Details are displayed if max score is > 0.2

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

Publications

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

ClinVar

Computational scores

Splicing

Publications

Other links and lift over