rs1555410445

chr15-63064099-A-G

Variant summary

Our verdict is Uncertain significance. Variant got 5 ACMG points: 5P and 0B. PM1 PM2 PP2

The NM_001018005.2(TPM1):c.808A>G(p.Ile270Val) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,836 control chromosomes in the GnomAD database, with no homozygous occurrence. 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. I270M) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: TPM1 NM_001018005.2 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 9.32

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 Uncertain_significance. Variant got 5 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
• PP2: Missense variant where missense usually causes diseases, TPM1

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TPM1	NM_001018005.2	c.808A>G	p.Ile270Val	missense_variant	9/10	ENST00000403994.9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TPM1	ENST00000403994.9	c.808A>G	p.Ile270Val	missense_variant	9/10	1	NM_001018005.2	A1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461836 Hom.: 0 Cov.: 31 AF XY: 0.00 AC XY: 0 AN XY: 727214

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome Cov.: 33

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

Invitae

Jul 19, 2022

This sequence change replaces isoleucine, which is neutral and non-polar, with valine, which is neutral and non-polar, at codon 270 of the TPM1 protein (p.Ile270Val). 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 tolerated. 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. ClinVar contains an entry for this variant (Variation ID: 454422). This variant has not been reported in the literature in individuals affected with TPM1-related conditions. This variant is not present in population databases (gnomAD no frequency). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.092
CardioboostCm	Benign	0.053
BayesDel_addAF	Pathogenic	0.24	D
BayesDel_noAF	Uncertain	0.11
Cadd	Uncertain	24
Dann	Uncertain	1.0
Eigen	Uncertain	0.22
Eigen_PC	Uncertain	0.40
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.87	D;D;D;D;D;D
M_CAP	Uncertain	0.13	D
MetaRNN	Uncertain	0.69	D;D;D;D;D;D
MetaSVM	Uncertain	0.73	D
MutationAssessor	Uncertain	2.2	M;M;M;.;.;.
MutationTaster	Benign	0.79	D;D;D;D;D;D;D;D;D;D;D;D
PROVEAN	Benign	-0.50	N;N;.;.;.;N
REVEL	Uncertain	0.54
Sift	Benign	0.059	T;T;.;.;.;T
Sift4G	Benign	0.15	T;T;.;.;.;T
Polyphen		0.0040, 0.0010	.;B;B;.;.;.
Vest4		0.52
MutPred		0.69		Loss of methylation at K268 (P = 0.0906);Loss of methylation at K268 (P = 0.0906);Loss of methylation at K268 (P = 0.0906);Loss of methylation at K268 (P = 0.0906);.;.;
MVP		0.65
ClinPred		0.71	D
GERP RS		5.8
Varity_R		0.24

Splicing

Name	Calibrated prediction	Score	Prediction
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: rs1555410445; hg19: chr15-63356298;