NM_001018005.2:c.2T>C

Variant names:

• chr15-63042831-T-C
• rs1475635564
• NM_001018005.2:c.2T>C

Variant summary

Our verdict is Likely benign. Variant got -2 ACMG points: 2P and 4B. PVS1_Moderate BS2

The NM_001018005.2(TPM1):​c.2T>C​(p.Met1?) variant causes a start lost change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000548 in 1,460,586 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 (★★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000055 (0 hom.)
• Consequence: TPM1 NM_001018005.2 start_lost
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:4
• Conservation: PhyloP100: 7.72

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_benign. Variant got -2 ACMG points.

• PVS1: Start lost variant, next in-frame start position is after 2 pathogenic variants. Next in-frame start position is after 21 CDS bases. Genomic position: 63042850. Lost 0.025 part of the original CDS.
• BS2: High AC in GnomAdExome4 at 8 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TPM1	NM_001018005.2	c.2T>C	p.Met1?	start_lost	Exon 1 of 10	ENST00000403994.9	NP_001018005.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TPM1	ENST00000403994.9	c.2T>C	p.Met1?	start_lost	Exon 1 of 10	1	NM_001018005.2	ENSP00000385107.4

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD3 exomes AF: 0.00000403 AC: 1 AN: 248122 Hom.: 0 AF XY: 0.00000743 AC XY: 1 AN XY: 134644

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000899

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000548 AC: 8 AN: 1460586 Hom.: 0 Cov.: 31 AF XY: 0.00000688 AC XY: 5 AN XY: 726688

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.0000757

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000450

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Hypertrophic cardiomyopathy Uncertain:2

Dec 18, 2023

All of Us Research Program, National Institutes of Health

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant results in the loss of the translation initiator methionine at codon 1 of the TPM1 gene. This variant is expected to disrupt translation initiation and result in an absent or truncated protein product. To our knowledge, functional studies have not been reported for this variant. This variant has been reported in two individuals affected with dilated cardiomyopathy (PMID: 24503780, 34486814). This variant has been identified in 1/248122 chromosomes in the general population by the Genome Aggregation Database (gnomAD). Clinical relevance of loss-of-function TPM1 truncation variants in autosomal dominant cardiovascular disorders is not clearly established. The available evidence is insufficient to determine the role of this variant in disease conclusively. Therefore, this variant is classified as a Variant of Uncertain Significance. -

Jul 25, 2022

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change affects the initiator methionine of the TPM1 mRNA. The next in-frame methionine is located at codon 8. The frequency data for this variant in the population databases is considered unreliable, as metrics indicate poor data quality at this position in the gnomAD database. This variant has not been reported in the literature in individuals affected with TPM1-related conditions. ClinVar contains an entry for this variant (Variation ID: 1374193). 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. -

Hypertrophic cardiomyopathy 3;C2678476:Dilated cardiomyopathy 1Y Uncertain:1

Jul 01, 2021

Fulgent Genetics, Fulgent Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

not provided Uncertain:1

Sep 03, 2024

GeneDx

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Identified in a patient with DCM who also harbored a likely pathogenic variant in the TRPM4 gene (PMID: 34486814); Not observed at significant frequency in large population cohorts (gnomAD); Initiation codon variant in a gene for which loss of function is not a known mechanism of disease; This variant is associated with the following publications: (PMID: 24503780, 34486814) -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.60	D
BayesDel_noAF	Pathogenic	0.58
CADD	Pathogenic	27
DANN	Uncertain	0.99
DEOGEN2	Uncertain	0.53	.;.;D;.;D;T;.;.;.;.;.
Eigen	Uncertain	0.62
Eigen_PC	Uncertain	0.60
FATHMM_MKL	Uncertain	0.88	D
LIST_S2	Uncertain	0.90	D;D;D;.;D;D;D;D;D;D;D
M_CAP	Pathogenic	0.97	D
MetaRNN	Pathogenic	0.97	D;D;D;D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.0	D
PROVEAN	Uncertain	-3.0	D;D;.;D;D;D;D;D;D;.;.
REVEL	Pathogenic	0.97
Sift	Pathogenic	0.0	D;D;.;D;D;D;D;D;D;.;.
Sift4G	Pathogenic	0.0	D;D;D;D;D;D;D;D;D;.;.
Polyphen		1.0, 1.0	.;.;.;.;D;D;.;.;.;D;.
Vest4		0.95
MutPred		0.78		Loss of stability (P = 0.0037);Loss of stability (P = 0.0037);Loss of stability (P = 0.0037);Loss of stability (P = 0.0037);Loss of stability (P = 0.0037);Loss of stability (P = 0.0037);Loss of stability (P = 0.0037);Loss of stability (P = 0.0037);Loss of stability (P = 0.0037);Loss of stability (P = 0.0037);Loss of stability (P = 0.0037);
MVP		0.98
ClinPred		1.0	D
GERP RS		4.5
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.95
gMVP		0.97

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: rs1475635564; hg19: chr15-63335030;