rs121917851

Positions:

chr8-63066056-G-A

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1PM2PP5_Very_Strong

The NM_000370.3(TTPA):c.400C>T(p.Arg134*) variant causes a stop gained change. The variant allele was found at a frequency of 0.0000564 in 1,612,366 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 Likely pathogenic (★★). Variant results in nonsense mediated mRNA decay.

Frequency

Genomes: 𝑓 0.000040 ( 0 hom., cov: 33)

Exomes 𝑓: 0.000058 ( 0 hom. )

Consequence

TTPA
NM_000370.3 stop_gained

Scores

Clinical Significance

Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:12O:1

Conservation

PhyloP100: 4.89

Variant links:

Genes affected

TTPA (HGNC:12404): (alpha tocopherol transfer protein) This gene encodes a soluble protein that binds alpha-trocopherol, a form of vitamin E, with high selectivity and affinity. This protein plays an important role in regulating vitamin E levels in the body by transporting vitamin E between membrane vesicles and facilitating the secretion of vitamin E from hepatocytes to circulating lipoproteins. Mutations in this gene cause hereditary vitamin E deficiency (ataxia with vitamin E deficiency, AVED) and retinitis pigmentosa. [provided by RefSeq, Nov 2009]

TTPA links:

TTPA (HGNC:):

TTPA links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Pathogenic. Variant got 18 ACMG points.

PVS1

Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.

PM2

Very rare variant in population databases, with high coverage;

PP5

Variant 8-63066056-G-A is Pathogenic according to our data. Variant chr8-63066056-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 9141.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr8-63066056-G-A is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TTPA	NM_000370.3 linkuse as main transcript	c.400C>T	p.Arg134*	stop_gained	3/5	ENST00000260116.5	NP_000361.1	P49638

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TTPA	ENST00000260116.5 linkuse as main transcript	c.400C>T	p.Arg134*	stop_gained	3/5	1	NM_000370.3	ENSP00000260116.4		P49638
TTPA	ENST00000521138.1 linkuse as main transcript	n.233-17453C>T		intron_variant		5

Frequencies

GnomAD3 genomes

AF:

0.0000398

AC:

AN:

150644

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.0000884

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.0000239

AC:

AN:

251282

Hom.:

AF XY:

0.0000221

AC XY:

AN XY:

135814

show subpopulations

Gnomad AFR exome

AF:

0.00

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:

0.0000462

Gnomad NFE exome

AF:

0.0000440

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.0000582

AC:

AN:

1461722

Hom.:

Cov.:

AF XY:

0.0000550

AC XY:

AN XY:

727156

show subpopulations

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:

0.0000187

Gnomad4 NFE exome

AF:

0.0000719

Gnomad4 OTH exome

AF:

0.0000662

GnomAD4 genome

AF:

0.0000398

AC:

AN:

150644

Hom.:

Cov.:

AF XY:

0.0000272

AC XY:

AN XY:

73474

show subpopulations

Gnomad4 AFR

AF:

0.00

Gnomad4 AMR

AF:

0.00

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.0000884

Gnomad4 OTH

AF:

0.00

Alfa

AF:

0.0000508

Hom.:

Bravo

AF:

0.0000604

ExAC

AF:

0.0000247

AC:

EpiCase

AF:

0.0000545

EpiControl

AF:

0.0000593

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:12Other:1

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

Familial isolated deficiency of vitamin E

Pathogenic:5Other:1

Pathogenic, criteria provided, single submitter	clinical testing	Fulgent Genetics, Fulgent Genetics	Apr 11, 2024	- -
Pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Dec 24, 2018	Variant summary: TTPA c.400C>T (p.Arg134X) results in a premature termination codon, predicted to cause a truncation of the encoded protein or absence of the protein due to nonsense mediated decay, which are commonly known mechanisms for disease. The variant allele was found at a frequency of 1.6e-05 in 246084 control chromosomes (gnomAD). c.400C>T has been reported in the literature in multiple homozygous and compound heterozygous individuals affected with Ataxia with Vitamin E Deficiency (Cavalier 1998, Euch-Fayache 2014, Elkamil 2015). These data indicate that the variant is very likely to be associated with disease. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014. Based on the evidence outlined above, the variant was classified as pathogenic. -
not provided, no classification provided	literature only	GeneReviews	-	- -
Likely pathogenic, criteria provided, single submitter	literature only	Counsyl	Jul 08, 2014	- -
Pathogenic, no assertion criteria provided	clinical testing	Natera, Inc.	Sep 16, 2020	- -
Pathogenic, criteria provided, single submitter	clinical testing	Baylor Genetics	Feb 27, 2024	- -

not provided

Pathogenic:4

Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Jan 20, 2024	This sequence change creates a premature translational stop signal (p.Arg134*) in the TTPA gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in TTPA are known to be pathogenic (PMID: 9463307, 26068213). This variant is present in population databases (rs121917851, gnomAD 0.004%). This premature translational stop signal has been observed in individuals with ataxia with isolated vitamin E deficiency (PMID: 9463307, 12470185, 22696689, 25614784). ClinVar contains an entry for this variant (Variation ID: 9141). For these reasons, this variant has been classified as Pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	Athena Diagnostics	Nov 07, 2022	This variant is expected to result in the loss of a functional protein. The frequency of this variant in the general population is consistent with pathogenicity (http://gnomad.broadinstitute.org). This variant has been identified in at least one individual with clinical features associated with this gene. -
Pathogenic, criteria provided, single submitter	clinical testing	CeGaT Center for Human Genetics Tuebingen	Apr 01, 2021	- -
Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Apr 20, 2023	Nonsense variant predicted to result in protein truncation or nonsense mediated decay in a gene for which loss of function is a known mechanism of disease; Not observed at significant frequency in large population cohorts (gnomAD); This variant is associated with the following publications: (PMID: 12899840, 12470185, 25525159, 20301419, 9463307, 22696689, 24369383, 19566498, 25614784, 32979145, 31589614, 32928973) -

Ataxia, Friedreich-like, with isolated vitamin E deficiency

Pathogenic:1

Pathogenic, no assertion criteria provided

literature only

OMIM

Feb 01, 1998

- -

TTPA-related disorder

Pathogenic:1

Pathogenic, no assertion criteria provided

clinical testing

PreventionGenetics, part of Exact Sciences

Mar 19, 2024

The TTPA c.400C>T variant is predicted to result in premature protein termination (p.Arg134*). This variant has been reported in the homozygous and compound heterozygous states in multiple patients with ataxia with isolated vitamin E deficiency (Cavalier et al. 1998. PubMed ID: 9463307; Koht et al. 2009. PubMed ID: 19566498; Elkamil et al. 2015. PubMed ID: 25614784). This variant is reported in 0.0046% of alleles in individuals of European (Finnish) descent in gnomAD. Nonsense variants in TTPA are expected to be pathogenic. This variant is interpreted as pathogenic. -

Retinal dystrophy

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Institute of Human Genetics, Univ. Regensburg, Univ. Regensburg

Jan 01, 2022

- -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_addAF

Pathogenic

0.58

BayesDel_noAF

Pathogenic

0.65

CADD

Pathogenic

DANN

Uncertain

1.0

Eigen

Pathogenic

0.90

Eigen_PC

Pathogenic

0.78

FATHMM_MKL

Uncertain

0.96

Vest4

0.84

GERP RS

5.5

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.14

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

Below is the list of publications found by LitVar. It may be empty.

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

LitVar

Other links and lift over