Genetic Variant TNNT3:p.Gly254Gly (chr11-1938477-C-G) – ACMG Classification: Likely_benign (-3 pts)

Variant summary

Our verdict is Likely benign. The variant received -3 ACMG points: 2P and 5B. PM2BP4_StrongBP7

The NM_006757.4(TNNT3):c.762C>G(p.Gly254Gly) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,460,994 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Synonymous variant affecting the same amino acid position (i.e. G254G) has been classified as Likely benign.

Frequency

Genomes: not found (cov: 33)

Exomes 𝑓: 6.8e-7 ( 0 hom. )

Consequence

TNNT3
NM_006757.4 synonymous

Scores

Clinical Significance

Not reported in ClinVar

Conservation

PhyloP100: -4.71

Publications

15 publications found

Variant links:

Genes affected

TNNT3 (HGNC:11950): (troponin T3, fast skeletal type) The binding of Ca(2+) to the trimeric troponin complex initiates the process of muscle contraction. Increased Ca(2+) concentrations produce a conformational change in the troponin complex that is transmitted to tropomyosin dimers situated along actin filaments. The altered conformation permits increased interaction between a myosin head and an actin filament which, ultimately, produces a muscle contraction. The troponin complex has protein subunits C, I, and T. Subunit C binds Ca(2+) and subunit I binds to actin and inhibits actin-myosin interaction. Subunit T binds the troponin complex to the tropomyosin complex and is also required for Ca(2+)-mediated activation of actomyosin ATPase activity. There are 3 different troponin T genes that encode tissue-specific isoforms of subunit T for fast skeletal-, slow skeletal-, and cardiac-muscle. This gene encodes fast skeletal troponin T protein; also known as troponin T type 3. Alternative splicing results in multiple transcript variants encoding additional distinct troponin T type 3 isoforms. A developmentally regulated switch between fetal/neonatal and adult troponin T type 3 isoforms occurs. Additional splice variants have been described but their biological validity has not been established. Mutations in this gene may cause distal arthrogryposis multiplex congenita type 2B (DA2B). [provided by RefSeq, Oct 2009]

TNNT3 Gene-Disease associations (from GenCC):

distal arthrogryposis type 2B1
Inheritance: AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae)
congenital myopathy
Inheritance: AR Classification: STRONG Submitted by: G2P
arthrogryposis, distal, type 2B2
Inheritance: AD Classification: MODERATE Submitted by: Ambry Genetics
nemaline myopathy
Inheritance: AR Classification: MODERATE, LIMITED Submitted by: Ambry Genetics, ClinGen
digitotalar dysmorphism
Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
Sheldon-hall syndrome
Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

TNNT3 links:

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ACMG classification

Classification was made for transcript

Our verdict: Likely_benign. The variant received -3 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

BP4

Computational evidence support a benign effect (BayesDel_noAF=-0.52).

BP7

Synonymous conserved (PhyloP=-4.71 with no splicing effect.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TNNT3	NM_006757.4 link	c.762C>G	p.Gly254Gly	synonymous_variant	Exon 16 of 16	ENST00000278317.11	NP_006748.1	P45378-2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TNNT3	ENST00000278317.11 link	c.762C>G	p.Gly254Gly	synonymous_variant	Exon 16 of 16	5	NM_006757.4	ENSP00000278317.6		P45378-2

Frequencies

GnomAD3 genomes

Cov.:

GnomAD2 exomes

AF:

0.00000404

AC:

AN:

247790

AF XY:

0.00

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.0000289

Gnomad ASJ exome

AF:

0.00

Gnomad EAS 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:

6.84e-7

AC:

AN:

1460994

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

726788

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

33474

American (AMR)

AF:

0.0000224

AC:

AN:

44714

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26120

East Asian (EAS)

AF:

0.00

AC:

AN:

39682

South Asian (SAS)

AF:

0.00

AC:

AN:

86256

European-Finnish (FIN)

AF:

0.00

AC:

AN:

52730

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5766

European-Non Finnish (NFE)

AF:

0.00

AC:

AN:

1111876

Other (OTH)

AF:

0.00

AC:

AN:

60376

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.575

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

GnomAD4 genome

Cov.:

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_noAF

Benign

-0.52

CADD

Benign

5.9

(source)

DANN

Benign

0.75

PhyloP100

-4.7

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

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

ClinVar

Computational scores

Splicing

Publications

Other links and lift over