chr8-63086020-A-G

Position:

chr8-63086020-A-G

Variant summary

Our verdict is Pathogenic. Variant got 20 ACMG points: 20P and 0B. PVS1PS1_ModeratePM2PP5_Very_Strong

The NM_000370.3(TTPA):c.2T>C(p.Met1?) variant causes a start lost change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000014 in 1,428,596 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 (★★).

Frequency

Genomes: 𝑓 0.000020 ( 0 hom., cov: 33)

Exomes 𝑓: 0.000013 ( 0 hom. )

Consequence

TTPA
NM_000370.3 start_lost

Scores

Clinical Significance

Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:6

Conservation

PhyloP100: -0.00800

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:

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ACMG classification

Classification made for transcript

Verdict is Pathogenic. Variant got 20 ACMG points.

PVS1

Start lost variant, no new inframe start found.

PS1

Another start lost variant in NM_000370.3 (TTPA) was described as [Pathogenic] in Lovd

PM2

Very rare variant in population databases, with high coverage;

PP5

Variant 8-63086020-A-G is Pathogenic according to our data. Variant chr8-63086020-A-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 189186.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TTPA	NM_000370.3 linkuse as main transcript	c.2T>C	p.Met1?	start_lost	1/5	ENST00000260116.5	NP_000361.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TTPA	ENST00000260116.5 linkuse as main transcript	c.2T>C	p.Met1?	start_lost	1/5	1	NM_000370.3	ENSP00000260116	P1
TTPA	ENST00000521138.1 linkuse as main transcript	n.30T>C		non_coding_transcript_exon_variant	1/2	5

Frequencies

GnomAD3 genomes

AF:

0.0000197

AC:

AN:

151910

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.0000655

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:

0.0000147

Gnomad OTH

AF:

0.000479

GnomAD4 exome

AF:

0.0000133

AC:

AN:

1276686

Hom.:

Cov.:

AF XY:

0.0000143

AC XY:

AN XY:

628708

show subpopulations

Gnomad4 AFR exome

AF:

0.00

Gnomad4 AMR exome

AF:

0.0000865

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:

0.00000975

Gnomad4 OTH exome

AF:

0.0000961

GnomAD4 genome

AF:

0.0000197

AC:

AN:

151910

Hom.:

Cov.:

AF XY:

0.0000135

AC XY:

AN XY:

74214

show subpopulations

Gnomad4 AFR

AF:

0.00

Gnomad4 AMR

AF:

0.0000655

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.0000147

Gnomad4 OTH

AF:

0.000479

Bravo

AF:

0.0000793

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:6

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

not provided

Pathogenic:3

Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Jul 29, 2023	For these reasons, this variant has been classified as Pathogenic. This variant disrupts the p.Arg59 amino acid residue in TTPA. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 9463307, 16819822, 17049453, 23599266). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. Experimental studies are conflicting or provide insufficient evidence to determine the effect of this variant on TTPA function (PMID: 3837850). Algorithms developed to predict the effect of variants on protein structure and function are not available or were not evaluated for this variant. Disruption of the initiator codon has been observed in individuals with ataxia with isolated vitamin E deficiency (PMID: 10360777, 31970222). This variant is not present in population databases (gnomAD no frequency). This sequence change affects the initiator methionine of the TTPA mRNA. The next in-frame methionine is located at codon 209. ClinVar contains an entry for this variant (Variation ID: 189186). -
Pathogenic, criteria provided, single submitter	clinical testing	Athena Diagnostics	Apr 26, 2017	- -
Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Apr 25, 2023	Initiation codon variant 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: 9485073, 31970222, 10360777) -

Familial isolated deficiency of vitamin E

Pathogenic:2

Likely pathogenic, criteria provided, single submitter	literature only	Counsyl	Feb 18, 2015	- -
Pathogenic, no assertion criteria provided	clinical testing	Natera, Inc.	Sep 16, 2020	- -

TTPA-related disorder

Pathogenic:1

Likely pathogenic, no assertion criteria provided

clinical testing

PreventionGenetics, part of Exact Sciences

Jun 03, 2024

The TTPA c.2T>C variant is predicted to disrupt the translation initiation site (Start loss). This variant has been reported in the homozygous and compound heterozygous states in individuals with ataxia with vitamin E deficiency (Hoshino et al. 1999. PubMed ID: 10360777; Pradeep et al. 2019. PubMed ID: 31970222). This variant has not been reported in a large population database, indicating this variant is rare. This variant is interpreted as likely pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_addAF

Pathogenic

0.63

BayesDel_noAF

Uncertain

0.0

CADD

Uncertain

DANN

Benign

0.96

DEOGEN2

Benign

0.25

Eigen

Benign

-0.67

Eigen_PC

Benign

-0.63

FATHMM_MKL

Benign

0.59

LIST_S2

Uncertain

0.90

M_CAP

Pathogenic

0.99

MetaRNN

Pathogenic

0.98

MetaSVM

Benign

-0.86

MutationTaster

Benign

1.0

PROVEAN

Benign

0.040

REVEL

Uncertain

0.41

Sift

Pathogenic

0.0

Sift4G

Uncertain

0.044

Polyphen

0.020

Vest4

0.83

MutPred

0.99

Gain of glycosylation at M1 (P = 0.0067);

MVP

0.66

ClinPred

0.99

GERP RS

-0.16

Varity_R

0.61

gMVP

0.60

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

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