rs199476320

Positions:

• chr15-63064121-C-G
• chr15-63064121-C-T

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PM1 PM2 PM5 PP2 PP3

The NM_001018005.2(TPM1):​c.830C>G​(p.Ala277Gly) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000657 in 152,234 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. A277T) has been classified as Uncertain significance.

• Frequency: Genomes: 𝑓 0.0000066 (0 hom., cov: 33)
• Consequence: TPM1 NM_001018005.2 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 7.91

Genes affected

TPM1 (HGNC:12010): (tropomyosin 1) This gene is a member of the tropomyosin family of highly conserved, widely distributed actin-binding proteins involved in the contractile system of striated and smooth muscles and the cytoskeleton of non-muscle cells. Tropomyosin is composed of two alpha-helical chains arranged as a coiled-coil. It is polymerized end to end along the two grooves of actin filaments and provides stability to the filaments. The encoded protein is one type of alpha helical chain that forms the predominant tropomyosin of striated muscle, where it also functions in association with the troponin complex to regulate the calcium-dependent interaction of actin and myosin during muscle contraction. In smooth muscle and non-muscle cells, alternatively spliced transcript variants encoding a range of isoforms have been described. Mutations in this gene are associated with type 3 familial hypertrophic cardiomyopathy and dilated cardiomyopathy 1Y. [provided by RefSeq, Jun 2022]

ACMG classification

Verdict is Likely_pathogenic. Variant got 8 ACMG points.

• PM1: In a coiled_coil_region (size 283) in uniprot entity TPM1_HUMAN there are 128 pathogenic changes around while only 5 benign (96%) in NM_001018005.2
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr15-63064121-C-T is described in Lovd as [Likely_pathogenic].
• PP2: Missense variant where missense usually causes diseases, TPM1
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.833

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TPM1	NM_001018005.2	c.830C>G	p.Ala277Gly	missense_variant	9/10	ENST00000403994.9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TPM1	ENST00000403994.9	c.830C>G	p.Ala277Gly	missense_variant	9/10	1	NM_001018005.2	A1

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152234 Hom.: 0 Cov.: 33

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.: 31

GnomAD4 genome AF: 0.00000657 AC: 1 AN: 152234 Hom.: 0 Cov.: 33 AF XY: 0.00 AC XY: 0 AN XY: 74362

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:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Dec 31, 2018

proposed classification - variant undergoing re-assessment, contact laboratory -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

GeneDx

Jul 13, 2012

The Ala277Gly variant in the TPM1 gene has not been reported previously as a disease-causing mutation or as a benign polymorphism, to our knowledge. However, Ala277Val has been reported in a patient with severe idiopathic DCM who required a heart transplant at age 13, and Ala277Val was absent from 413 control individuals of various ethnic backgrounds (Hershberger R et al., 2010; Rampersaud E et al., 2011). However, this individual also harbored a mutation in the TNNT2 gene (Hershberger R et al., 2010; Rampersaud E et al., 2011). Ala277Gly is a conservative amino acid substitution of one non-polar amino acid for another at a position that is conserved across species. A mutation in a nearby codon (Met281Thr) has been reported in association with cardiomyopathy, supporting the functional importance of this region of the protein. Furthermore, the NHLBI ESP Exome Variant Server reports Ala277Gly was not observed in over 5,000 samples from individuals of European and African American backgrounds, indicating it is not a common variant in these populations. In summary, with the clinical and molecular information available at this time, we cannot determine whether Ala277Gly in the TPM1 gene is a disease-causing mutation or a benign variant. The variant is found in DCM panel(s). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.75
CardioboostCm	Uncertain	0.43
BayesDel_addAF	Pathogenic	0.42	D
BayesDel_noAF	Pathogenic	0.37
CADD	Pathogenic	27
DANN	Uncertain	1.0
Eigen	Uncertain	0.49
Eigen_PC	Uncertain	0.59
FATHMM_MKL	Uncertain	0.97	D
LIST_S2	Uncertain	0.94	D;D;D;D;D;D
M_CAP	Pathogenic	0.50	D
MetaRNN	Pathogenic	0.83	D;D;D;D;D;D
MetaSVM	Pathogenic	1.0	D
MutationAssessor	Pathogenic	3.3	M;M;M;.;.;.
MutationTaster	Benign	1.0	D;D;D;D;D;D;D;D;D;D;D;D
PROVEAN	Benign	-2.0	N;N;.;.;.;N
REVEL	Pathogenic	0.83
Sift	Uncertain	0.0010	D;D;.;.;.;D
Sift4G	Pathogenic	0.0010	D;D;.;.;.;D
Polyphen		0.010, 0.18	.;B;B;.;.;.
Vest4		0.71
MutPred		0.59		Loss of stability (P = 0.0211);Loss of stability (P = 0.0211);Loss of stability (P = 0.0211);Loss of stability (P = 0.0211);.;.;
MVP		0.94
ClinPred		0.87	D
GERP RS		5.8
Varity_R		0.65

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: rs199476320; hg19: chr15-63356320;