1-201359618-C-T

Position:

• chr1-201359618-C-T

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 2P and 0B. PM2

The NM_001276345.2(TNNT2):​c.851+5G>A variant causes a splice donor 5th base, intron change. The variant allele was found at a frequency of 0.000000691 in 1,447,102 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.9e-7 (0 hom.)
• Consequence: TNNT2 NM_001276345.2 splice_donor_5th_base, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:3
• Conservation: PhyloP100: 6.83

Genes affected

TNNT2 (HGNC:11949): (troponin T2, cardiac type) This gene encodes the cardiac isoform of troponin T. The encoded protein is the tropomyosin-binding subunit of the troponin complex, which is located on the thin filament of striated muscles and regulates muscle contraction in response to alterations in intracellular calcium ion concentration. Mutations in this gene have been associated with familial hypertrophic cardiomyopathy as well as with dilated cardiomyopathy. [provided by RefSeq, May 2022]

ACMG classification

Verdict is Uncertain_significance. Variant got 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TNNT2	NM_001276345.2	c.851+5G>A		splice_donor_5th_base_variant, intron_variant		ENST00000656932.1	NP_001263274.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TNNT2	ENST00000656932.1	c.851+5G>A		splice_donor_5th_base_variant, intron_variant			NM_001276345.2	ENSP00000499593	A2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.91e-7 AC: 1 AN: 1447102 Hom.: 0 Cov.: 32 AF XY: 0.00000139 AC XY: 1 AN XY: 718260

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: 9.06e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:3

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Feb 06, 2024

Not observed in large population cohorts (gnomAD); In silico analysis supports a deleterious effect on splicing; Identified in a patient with hypertrophic cardiomyopathy in the published literature (PMID: 36204818); This variant is associated with the following publications: (PMID: 37652022, 36204818) -

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Feb 05, 2019

Variant summary: TNNT2 c.821+5G>A alters a conserved nucleotide located close to a canonical splice site and therefore could affect mRNA splicing, leading to a significantly altered protein sequence. Several computational tools predict a significant impact on normal splicing: four predict the variant abolishes a 5' splicing donor site (ACMG PP3). However, these predictions have yet to be confirmed by functional studies. The variant was absent in 222940 control chromosomes (gnomAD) (ACMG PM2). The available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. To our knowledge, no occurrence of c.821+5G>A in individuals affected with Cardiomyopathy and no experimental evidence demonstrating its impact on protein function have been reported in the literature. One clinical diagnostic laboratory has submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation, and classified the variant as likely pathogenic while noting that it has been identified independently of additional cardiogenetic variants in several individuals referred for HCM genetic testing at their laboratory (GeneDx 2016). However, the exact number of functional meiotic transmissions is not specified, therefore, we have not considered this information to support co-segregation within the context of our evaluation at this time. This variant was initially identified in one adult (age >40) male patient referred for a Familial Cardiomyopathy evaluation at our laboratory. However, this patient is lost to follow-up and no information pertaining to clinical history and/or co-segregation with disease is available at this time. Other variants affecting the same canonical splice site (c.821+1G>A, c.821+1G>C and c.821+1G>T) have been reported in association with HCM (HGMD and in the Atlas of Cardiac Genetic Variation database) but that does not unequivocally prove causation for this variant located outside of the canonical splice site in the TNNT2 gene. Therefore, based strictly on the limited information available as outlined above, the variant was classified as VUS-possibly pathogenic. -

Cardiomyopathy Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

CHEO Genetics Diagnostic Laboratory, Children's Hospital of Eastern Ontario

Jan 05, 2018

- -

Dilated cardiomyopathy 1D;C1861864:Hypertrophic cardiomyopathy 2;C2676271:Cardiomyopathy, familial restrictive, 3 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jan 11, 2024

This sequence change falls in intron 15 of the TNNT2 gene. It does not directly change the encoded amino acid sequence of the TNNT2 protein. It affects a nucleotide within the consensus splice site. This variant is not present in population databases (gnomAD no frequency). This variant has been observed in individual(s) with hypertrophic cardiomyopathy (PMID: 36204818). ClinVar contains an entry for this variant (Variation ID: 36886). Variants that disrupt the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.16
CADD	Benign	21
DANN	Benign	0.95

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.99
SpliceAI score (max)		0.56		Details are displayed if max score is > 0.2
DS_DG_spliceai		0.40		Position offset: -8
DS_DL_spliceai		0.56		Position offset: 5

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs193922620; hg19: chr1-201328746;