18-3164337-G-A

Position:

• chr18-3164337-G-A

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PM2 PP3_Moderate

The NM_003803.4(MYOM1):​c.1442C>T​(p.Thr481Ile) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: not found (cov: 33)
• Consequence: MYOM1 NM_003803.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 7.66

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]

ACMG classification

Verdict is Uncertain_significance. Variant got 4 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.887

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MYOM1	NM_003803.4	c.1442C>T	p.Thr481Ile	missense_variant	10/38	ENST00000356443.9	NP_003794.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MYOM1	ENST00000356443.9	c.1442C>T	p.Thr481Ile	missense_variant	10/38	1	NM_003803.4	ENSP00000348821	P2
MYOM1	ENST00000261606.11	c.1442C>T	p.Thr481Ile	missense_variant	10/37	1		ENSP00000261606	A2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 33

Bravo AF: 0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Hypertrophic cardiomyopathy Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jul 01, 2022

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. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive. This variant has not been reported in the literature in individuals affected with MYOM1-related conditions. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces threonine, which is neutral and polar, with isoleucine, which is neutral and non-polar, at codon 481 of the MYOM1 protein (p.Thr481Ile). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.57
BayesDel_addAF	Pathogenic	0.40	D
BayesDel_noAF	Pathogenic	0.34
CADD	Uncertain	24
DANN	Uncertain	1.0
DEOGEN2	Benign	0.32	T;.;.
Eigen	Uncertain	0.67
Eigen_PC	Uncertain	0.60
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Uncertain	0.95	D;D;D
M_CAP	Uncertain	0.094	D
MetaRNN	Pathogenic	0.89	D;D;D
MetaSVM	Uncertain	0.41	D
MutationAssessor	Pathogenic	3.1	M;.;M
MutationTaster	Benign	1.0	D;D;D
PrimateAI	Uncertain	0.65	T
PROVEAN	Pathogenic	-4.8	D;.;D
REVEL	Pathogenic	0.78
Sift	Uncertain	0.0050	D;.;D
Sift4G	Uncertain	0.0030	D;D;D
Polyphen		0.98	D;.;P
Vest4		0.89
MutPred		0.57		Loss of disorder (P = 0.064);.;Loss of disorder (P = 0.064);
MVP		0.95
MPC		0.62
ClinPred		0.99	D
GERP RS		4.9
Varity_R		0.54
gMVP		0.68

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: rs370177143; hg19: chr18-3164335;