chr18-3135669-C-A

Position:

• chr18-3135669-C-A

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM2 PM5 PP3_Moderate

The NM_003803.4(MYOM1):​c.2087G>T​(p.Arg696Leu) variant causes a missense change. The variant allele was found at a frequency of 0.00000616 in 1,461,696 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 Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R696H) has been classified as Pathogenic.

• Frequency:
  • Genomes: not found (cov: 31)
  • Exomes 𝑓: 0.0000062 (0 hom.)
• Consequence: MYOM1 NM_003803.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 5.80

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 Likely_pathogenic. Variant got 6 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr18-3135669-C-T is described in Lovd as [Pathogenic].
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.893

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MYOM1	NM_003803.4	c.2087G>T	p.Arg696Leu	missense_variant	15/38	ENST00000356443.9	NP_003794.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MYOM1	ENST00000356443.9	c.2087G>T	p.Arg696Leu	missense_variant	15/38	1	NM_003803.4	ENSP00000348821.4
MYOM1	ENST00000261606.11	c.2087G>T	p.Arg696Leu	missense_variant	15/37	1		ENSP00000261606.7
MYOM1	ENST00000577294.1	n.143G>T		non_coding_transcript_exon_variant	2/2	2

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD3 exomes AF: 0.0000161 AC: 4 AN: 249148 Hom.: 0 AF XY: 0.0000148 AC XY: 2 AN XY: 135182

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000869

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: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000616 AC: 9 AN: 1461696 Hom.: 0 Cov.: 30 AF XY: 0.00000963 AC XY: 7 AN XY: 727128

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.0000894

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.0000464

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 8.99e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 31

ExAC AF: 0.0000165 AC: 2

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

Oct 13, 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. 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 MYOM1 protein function. This variant has not been reported in the literature in individuals affected with MYOM1-related conditions. This variant is present in population databases (rs767192545, gnomAD 0.009%). This sequence change replaces arginine, which is basic and polar, with leucine, which is neutral and non-polar, at codon 696 of the MYOM1 protein (p.Arg696Leu). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.55
BayesDel_addAF	Pathogenic	0.18	D
BayesDel_noAF	Pathogenic	0.21
CADD	Uncertain	25
DANN	Uncertain	1.0
DEOGEN2	Benign	0.23	T;.;.
Eigen	Pathogenic	0.75
Eigen_PC	Pathogenic	0.71
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Pathogenic	0.98	D;D;D
M_CAP	Uncertain	0.095	D
MetaRNN	Pathogenic	0.89	D;D;D
MetaSVM	Uncertain	-0.15	T
MutationAssessor	Uncertain	2.8	M;.;M
PrimateAI	Uncertain	0.57	T
PROVEAN	Pathogenic	-6.5	D;.;D
REVEL	Uncertain	0.54
Sift	Uncertain	0.0020	D;.;D
Sift4G	Pathogenic	0.0	D;D;D
Polyphen		1.0	D;.;D
Vest4		0.93
MutPred		0.71		Loss of sheet (P = 0.0357);.;Loss of sheet (P = 0.0357);
MVP		0.89
MPC		0.68
ClinPred		0.99	D
GERP RS		5.1
Varity_R		0.72
gMVP		0.72

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: rs767192545; hg19: chr18-3135667;