NM_001018005.2:c.148C>A

Variant names:

• chr15-63044060-C-A
• rs1060501866
• NM_001018005.2:c.148C>A

Variant summary

Our verdict is Uncertain significance. The variant received 4 ACMG points: 6P and 2B. PM1 PM2 PM5 BP4 BP6

The NM_001018005.2(TPM1):​c.148C>A​(p.Leu50Ile) variant causes a missense change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. L50F) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: TPM1 NM_001018005.2 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:2 B:1
• Conservation: PhyloP100: 3.80
• Publications: 1 publications found

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]

TPM1-AS (HGNC:53635): (TPM1 antisense RNA)

ACMG classification

Our verdict: Uncertain_significance. The variant received 4 ACMG points.

• PM1: In a hotspot region, there are 5 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 15 uncertain 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 chr15-63044060-C-T is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 454415.
• BP4: Computational evidence support a benign effect (MetaRNN=0.3247916).
• BP6: Variant 15-63044060-C-A is Benign according to our data. Variant chr15-63044060-C-A is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 408135.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TPM1	NM_001018005.2	c.148C>A	p.Leu50Ile	missense_variant	Exon 2 of 10	ENST00000403994.9	NP_001018005.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TPM1	ENST00000403994.9	c.148C>A	p.Leu50Ile	missense_variant	Exon 2 of 10	1	NM_001018005.2	ENSP00000385107.4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 33

GnomAD4 genome Cov.: 32

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:2 Benign:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Hypertrophic cardiomyopathy Uncertain:1

Feb 02, 2025

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces leucine, which is neutral and non-polar, with isoleucine, which is neutral and non-polar, at codon 50 of the TPM1 protein (p.Leu50Ile). This variant is not present in population databases (gnomAD no frequency). 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: 408135). An algorithm developed to predict the effect of missense changes on protein structure and function (PolyPhen-2) suggests 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. -

Cardiovascular phenotype Uncertain:1

Dec 25, 2023

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.L50I variant (also known as c.148C>A), located in coding exon 2 of the TPM1 gene, results from a C to A substitution at nucleotide position 148. The leucine at codon 50 is replaced by isoleucine, an amino acid with highly similar properties. This amino acid position is conserved. In addition, the in silico prediction for this alteration is inconclusive. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

not provided Benign:1

Mar 03, 2015

GeneDx

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.15
CardioboostCm	Benign	0.012
BayesDel_addAF	Pathogenic	0.18	D
BayesDel_noAF	Uncertain	0.010
CADD	Uncertain	25
DANN	Benign	0.93
DEOGEN2	Benign	0.26	.;.;T;.;D;T;.;.
Eigen	Benign	-0.20
Eigen_PC	Benign	0.058
FATHMM_MKL	Uncertain	0.88	D
LIST_S2	Uncertain	0.96	D;D;D;.;D;D;D;D
M_CAP	Benign	0.081	D
MetaRNN	Benign	0.32	T;T;T;T;T;T;T;T
MetaSVM	Uncertain	0.28	D
MutationAssessor	Benign	-0.18	N;N;.;.;N;.;N;.
PhyloP100		3.8
PROVEAN	Benign	-0.14	N;N;.;N;N;N;N;.
REVEL	Uncertain	0.40
Sift	Benign	0.23	T;T;.;T;T;T;T;.
Sift4G	Benign	0.90	T;T;T;T;T;T;T;.
Polyphen		0.0010, 0.0020	.;.;.;.;B;B;.;.
Vest4		0.60
MutPred		0.67		.;.;.;.;.;Gain of methylation at K91 (P = 0.0634);.;.;
MVP		0.85
MPC		1.5
ClinPred		0.69	D
GERP RS		5.6
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.34
gMVP		0.93
Mutation Taster		=53/47	polymorphism

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

Other links and lift over

dbSNP: rs1060501866; hg19: chr15-63336259;