rs199476312

chr15-63060891-T-C

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM1 PM2 PP2 PP3

The NM_001018005.2(TPM1):c.515T>C(p.Ile172Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000274 in 1,461,878 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. I172M) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000027 (0 hom.)
• Consequence: TPM1 NM_001018005.2 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts P:1 U:5 O:1
• Conservation: PhyloP100: 8.02

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 6 ACMG points.

• PM1: In a hotspot region, there are 6 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 6 uncertain in NM_001018005.2
• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant where missense usually causes diseases, TPM1
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.771

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TPM1	NM_001018005.2	c.515T>C	p.Ile172Thr	missense_variant	5/10	ENST00000403994.9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TPM1	ENST00000403994.9	c.515T>C	p.Ile172Thr	missense_variant	5/10	1	NM_001018005.2	A1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251434 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135888

Gnomad AFR exome AF: 0.0000615

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: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000274 AC: 4 AN: 1461878 Hom.: 0 Cov.: 32 AF XY: 0.00000413 AC XY: 3 AN XY: 727242

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: 0.0000116

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000270

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ESP6500AA AF: 0.000227 AC: 1

ESP6500EA AF: 0.00 AC: 0

ExAC AF: 0.00000824 AC: 1

ClinVar

Significance: Uncertain significance

Submissions summary: Pathogenic:1 Uncertain:5 Other:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:1 Uncertain:1 Other:1

Likely pathogenic, flagged submission	clinical testing	Blueprint Genetics	Nov 02, 2017	- -
not provided, no classification provided	curation	Leiden Muscular Dystrophy (TPM1)	Apr 15, 2012	- -
Uncertain significance, criteria provided, single submitter	clinical testing	GeneDx	May 31, 2018	A variant of uncertain significance has been identified in the TPM1 gene. The I172T variant was reported as novel in one patient with HCM and a family history of HCM as well as sudden cardiac death (Van Driest et al., 2003). However, this study cohort was screened only for thin filament variants. Subsequently, Van Driest et al. (2004) reported I172T in an individual with HCM who also harbored an MYBPC3 variant, presumably the same patient from the 2003 study due to cohort overlap. Additionally, one functional study suggests that this variant does not impact protein function (Gupte et al., 2015), whereas a more recent functional study suggests this variant may lead to a milder phenotype (Matyushenko et al., 2017). Nevertheless, the I172T variant is not observed in large population cohorts (Lek et al., 2016). This variant is a non-conservative amino acid substitution, which is likely to impact secondary protein structure as these residues differ in polarity, charge, size and/or other properties. Finally, in-silico analyses, including protein predictors and evolutionary conservation, support a deleterious effect. Therefore, based on the currently available information, it is unclear whether this variant is pathogenic or rare benign. -

Hypertrophic cardiomyopathy Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	All of Us Research Program, National Institutes of Health	Jun 15, 2023	This variant has been reported in multiple individuals with hypertrophic cardiomyopathy (PMID: 33673806, 33495597, 23299917, 33495596, 33673806, 12860912, 15519027). This variant is present in 1/251434 total alleles in the Genome Aggregation Database (http://gnomad.broadinstitute.org/). This variant is predicted to be deleterious by in silico analysis. Functional studies suggest that this variant may result in a mild phenotype; however, additional studies are needed (PMID: 25548289, 27983818). -
Uncertain significance, criteria provided, single submitter	clinical testing	Invitae	May 26, 2022	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. Experimental studies are conflicting or provide insufficient evidence to determine the effect of this variant on TPM1 function (PMID: 25548289, 27983818). 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: "Probably Damaging"; Align-GVGD: "Class C0"). ClinVar contains an entry for this variant (Variation ID: 31879). This missense change has been observed in individual(s) with hypertrophic cardiomyopathy (PMID: 12860912, 15519027, 33673806). This variant is not present in population databases (gnomAD no frequency). This sequence change replaces isoleucine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 172 of the TPM1 protein (p.Ile172Thr). -

Primary familial hypertrophic cardiomyopathy Uncertain:2

Uncertain significance, no assertion criteria provided	research	CSER _CC_NCGL, University of Washington	Jun 01, 2014	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Molecular Diagnostic Laboratory for Inherited Cardiovascular Disease, Montreal Heart Institute	Mar 21, 2017	- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.30
CardioboostCm	Pathogenic	0.90
BayesDel_addAF	Pathogenic	0.53	D
BayesDel_noAF	Pathogenic	0.53
Cadd	Uncertain	25
Dann	Uncertain	1.0
Eigen	Benign	0.098
Eigen_PC	Uncertain	0.29
FATHMM_MKL	Uncertain	0.95	D
LIST_S2	Benign	0.84	T;T;T;T;T;T;T;T;T;T;T;T;T;T;T;T
M_CAP	Uncertain	0.28	D
MetaRNN	Pathogenic	0.77	D;D;D;D;D;D;D;D;D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	0.89	D
MutationAssessor	Benign	1.3	L;L;L;.;L;L;L;L;.;.;.;.;.;.;.;.
MutationTaster	Benign	1.0	D;D;D;D;D;D;D;D;D;D;D;D;D
PrimateAI	Pathogenic	0.87	D
PROVEAN	Uncertain	-2.8	D;D;D;D;D;D;D;.;.;D;D;.;D;D;D;D
REVEL	Pathogenic	0.80
Sift	Benign	0.066	T;T;T;T;T;T;T;.;.;T;D;.;D;D;T;D
Sift4G	Benign	0.44	T;T;T;T;T;T;T;.;.;T;T;.;T;T;T;T
Polyphen		0.0010, 0.74	.;.;B;B;.;.;.;B;.;.;.;.;.;P;.;.
Vest4		0.94
MVP		0.98
MPC		2.3
ClinPred		0.92	D
GERP RS		5.8
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.55
gMVP		0.92

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: rs199476312; hg19: chr15-63353090;