chr14-23431420-G-T

Position:

• chr14-23431420-G-T

Variant summary

Our verdict is Likely pathogenic. Variant got 7 ACMG points: 7P and 0B. PM1 PM2 PP2 PP3_Moderate

The NM_000257.4(MYH7):​c.794C>A​(p.Thr265Asn) variant causes a missense, splice region change. The variant allele was found at a frequency of 0.00000657 in 152,166 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predict no significant impact on normal splicing. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency: Genomes: 𝑓 0.0000066 (0 hom., cov: 32)
• Consequence: MYH7 NM_000257.4 missense, splice_region
• Scores: Splicing: ADA: 0.3304
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 6.61

Genes affected

MYH7 (HGNC:7577): (myosin heavy chain 7) Muscle myosin is a hexameric protein containing 2 heavy chain subunits, 2 alkali light chain subunits, and 2 regulatory light chain subunits. This gene encodes the beta (or slow) heavy chain subunit of cardiac myosin. It is expressed predominantly in normal human ventricle. It is also expressed in skeletal muscle tissues rich in slow-twitch type I muscle fibers. Changes in the relative abundance of this protein and the alpha (or fast) heavy subunit of cardiac myosin correlate with the contractile velocity of cardiac muscle. Its expression is also altered during thyroid hormone depletion and hemodynamic overloading. Mutations in this gene are associated with familial hypertrophic cardiomyopathy, myosin storage myopathy, dilated cardiomyopathy, and Laing distal myopathy. [provided by RefSeq, May 2022]

ACMG classification

Verdict is Likely_pathogenic. Variant got 7 ACMG points.

• PM1: In a strand (size 10) in uniprot entity MYH7_HUMAN there are 9 pathogenic changes around while only 0 benign (100%) in NM_000257.4
• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), MYH7. . Gene score misZ 3.9329 (greater than the threshold 3.09). Trascript score misZ 6.7889 (greater than threshold 3.09). GenCC has associacion of gene with hyaline body myopathy, MYH7-related skeletal myopathy, dilated cardiomyopathy 1S, congenital myopathy 7A, myosin storage, autosomal dominant, dilated cardiomyopathy, left ventricular noncompaction, myopathy, myosin storage, autosomal dominant, hypertrophic cardiomyopathy, congenital heart disease, Ebstein anomaly, arrhythmogenic right ventricular cardiomyopathy, myopathy, myosin storage, autosomal recessive, hypertrophic cardiomyopathy 1, familial isolated dilated cardiomyopathy.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.917

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MYH7	NM_000257.4	c.794C>A	p.Thr265Asn	missense_variant, splice_region_variant	9/40	ENST00000355349.4	NP_000248.2
MYH7	NM_001407004.1	c.794C>A	p.Thr265Asn	missense_variant, splice_region_variant	8/39		NP_001393933.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MYH7	ENST00000355349.4	c.794C>A	p.Thr265Asn	missense_variant, splice_region_variant	9/40	1	NM_000257.4	ENSP00000347507	P1

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152166 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.00

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: 0.0000147

Gnomad OTH AF: 0.00

GnomAD4 exome Cov.: 33

GnomAD4 genome AF: 0.00000657 AC: 1 AN: 152166 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 74330

Gnomad4 AFR AF: 0.00

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: 0.0000147

Gnomad4 OTH AF: 0.00

Bravo AF: 0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not specified Uncertain:1

Uncertain significance, no assertion criteria provided

clinical testing

Stanford Center for Inherited Cardiovascular Disease, Stanford University

Jan 16, 2012

Note this variant was found in clinical genetic testing performed by one or more labs who may also submit to ClinVar. Thus any internal case data may overlap with the internal case data of other labs. The interpretation reviewed below is that of the Stanford Center for Inherited Cardiovascular Disease. MYH7 p.Thr265Asn (c.794C>A) The variant is novel. There is no variation at codon 265 listed in the Exome Aggregation Consortium dataset (http://exac.broadinstitute.org/), which currently includes variant calls on ~64,000 individuals of European, African, Latino and Asian descent (as of December 22nd, 2014). -

Hypertrophic cardiomyopathy Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Oct 16, 2020

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. This variant is found within a region of MYH7 between codons 181 and 937 that contains the majority of the myosin head domain. Missense variants in this region have been shown to be significantly overrepresented in individuals with hypertrophic cardiomyopathy (PMID: 27532257). Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Benign"; Align-GVGD: "Class C0"). This variant has been observed in individual(s) with clinical features of hypertrophic cardiomyopathy (PMID: 27247418, Invitae). ClinVar contains an entry for this variant (Variation ID: 235035). This variant is not present in population databases (ExAC no frequency). This sequence change replaces threonine with asparagine at codon 265 of the MYH7 protein (p.Thr265Asn). The threonine residue is highly conserved and there is a small physicochemical difference between threonine and asparagine. -

Cardiovascular phenotype Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Apr 18, 2024

The p.T265N variant (also known as c.794C>A), located in coding exon 7 of the MYH7 gene, results from a C to A substitution at nucleotide position 794. The threonine at codon 265 is replaced by asparagine, an amino acid with similar properties. This alteration is located in the myosin head domain, which contains a statistically significant clustering of pathogenic missense variants (Homburger JR et al. Proc Natl Acad Sci U S A, 2016 06;113:6701-6; Walsh R et al. Genet Med, 2017 02;19:192-203; Ambry internal data). This alteration has been reported in a hypertrophic cardiomyopathy (HCM) cohort (Ho CY et al. Circulation, 2018 Oct;138:1387-1398). This amino acid position is highly conserved in available vertebrate species. In addition, the in silico prediction for this alteration is inconclusive. Based on the available evidence, the clinical significance of this variant remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.56
CardioboostCm	Uncertain	0.79
BayesDel_addAF	Uncertain	0.082	D
BayesDel_noAF	Benign	-0.12
CADD	Pathogenic	30
DANN	Uncertain	0.98
DEOGEN2	Pathogenic	0.88	D
Eigen	Benign	0.13
Eigen_PC	Benign	0.15
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.87	D
M_CAP	Pathogenic	0.86	D
MetaRNN	Pathogenic	0.92	D
MetaSVM	Uncertain	0.55	D
MutationAssessor	Benign	1.9	L
MutationTaster	Benign	1.0	D
PrimateAI	Pathogenic	0.84	D
PROVEAN	Uncertain	-2.6	D
REVEL	Uncertain	0.63
Sift	Uncertain	0.0040	D
Sift4G	Uncertain	0.046	D
Polyphen		0.15	B
Vest4		0.77
MutPred		0.61		Gain of catalytic residue at L268 (P = 0.0398);
MVP		0.96
MPC		1.4
ClinPred		0.91	D
GERP RS		3.5
Varity_R		0.74
gMVP		0.92

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Benign	0.33
dbscSNV1_RF	Benign	0.43
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

LitVar

Other links and lift over

dbSNP: rs876661375; hg19: chr14-23900629;