Genetic Variant MYOM1:p.Asn446Lys (chr18-3168818-G-T) – 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_003803.4(MYOM1):c.1338C>A(p.Asn446Lys) variant causes a missense, splice region change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,384 control chromosomes in the GnomAD database, with no homozygous occurrence. 3/3 splice prediction tools predict no significant impact on normal splicing. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Synonymous variant affecting the same amino acid position (i.e. N446N) has been classified as Likely benign.

Frequency

Genomes: not found (cov: 32)

Exomes 𝑓: 6.8e-7 ( 0 hom. )

Consequence

MYOM1
NM_003803.4 missense, splice_region

Scores

Splicing: ADA: 0.007928

Clinical Significance

Not reported in ClinVar

Conservation

PhyloP100: 2.58

Publications

0 publications found

Variant links:

Genes affected

MYOM1 (HGNC:7613): (myomesin 1) The giant protein titin, together with its associated proteins, interconnects the major structure of sarcomeres, the M bands and Z discs. The C-terminal end of the titin string extends into the M line, where it binds tightly to M-band constituents of apparent molecular masses of 190 kD (myomesin 1) and 165 kD (myomesin 2). This protein, myomesin 1, like myomesin 2, titin, and other myofibrillar proteins contains structural modules with strong homology to either fibronectin type III (motif I) or immunoglobulin C2 (motif II) domains. Myomesin 1 and myomesin 2 each have a unique N-terminal region followed by 12 modules of motif I or motif II, in the arrangement II-II-I-I-I-I-I-II-II-II-II-II. The two proteins share 50% sequence identity in this repeat-containing region. The head structure formed by these 2 proteins on one end of the titin string extends into the center of the M band. The integrating structure of the sarcomere arises from muscle-specific members of the superfamily of immunoglobulin-like proteins. Alternatively spliced transcript variants encoding different isoforms have been identified. [provided by RefSeq, Jul 2008]

MYOM1 Gene-Disease associations (from GenCC):

hypertrophic cardiomyopathy
Inheritance: AD Classification: NO_KNOWN Submitted by: ClinGen

MYOM1 links:

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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
MYOM1	NM_003803.4 link	c.1338C>A	p.Asn446Lys	missense_variant, splice_region_variant	Exon 9 of 38	ENST00000356443.9	NP_003794.3	P52179-1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
MYOM1	ENST00000356443.9 link	c.1338C>A	p.Asn446Lys	missense_variant, splice_region_variant	Exon 9 of 38	1	NM_003803.4	ENSP00000348821.4		P52179-1
MYOM1	ENST00000261606.11 link	c.1338C>A	p.Asn446Lys	missense_variant, splice_region_variant	Exon 9 of 37	1		ENSP00000261606.7		P52179-2

Frequencies

GnomAD3 genomes

Cov.:

GnomAD4 exome

AF:

6.84e-7

AC:

AN:

1461384

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

726964

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:

33480

American (AMR)

AF:

0.00

AC:

AN:

44700

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26128

East Asian (EAS)

AF:

0.00

AC:

AN:

39680

South Asian (SAS)

AF:

0.00

AC:

AN:

86234

European-Finnish (FIN)

AF:

0.00

AC:

AN:

53396

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5766

European-Non Finnish (NFE)

AF:

9.00e-7

AC:

AN:

1111640

Other (OTH)

AF:

0.00

AC:

AN:

60360

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.000000), 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

Pathogenic

0.81

BayesDel_addAF

Uncertain

0.035

BayesDel_noAF

Benign

-0.19

CADD

Benign

(source)

DANN

Uncertain

1.0

DEOGEN2

Benign

0.28

T;.;.

Eigen

Uncertain

0.29

Eigen_PC

Uncertain

0.27

FATHMM_MKL

Uncertain

0.85

LIST_S2

Uncertain

0.96

D;D;D

M_CAP

Uncertain

0.15

MetaRNN

Uncertain

0.72

D;D;D

MetaSVM

Uncertain

0.074

MutationAssessor

Benign

1.9

M;.;M

PhyloP100

2.6

PrimateAI

Uncertain

0.53

PROVEAN

Uncertain

-3.2

D;.;D

REVEL

Uncertain

0.61

Sift

Uncertain

0.0030

D;.;D

Sift4G

Uncertain

0.0050

D;D;D

Polyphen

1.0

D;.;D

Vest4

0.54

MutPred

0.66

Gain of MoRF binding (P = 0.03);.;Gain of MoRF binding (P = 0.03);

MVP

0.89

MPC

0.66

ClinPred

0.99

GERP RS

4.4

Varity_R

0.56

gMVP

0.48

Mutation Taster

=47/53

disease causing

(source)

Splicing

Name

Calibrated prediction

Score

Prediction

dbscSNV1_ADA

Benign

0.0079

dbscSNV1_RF

Benign

0.27

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

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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