NM_000370.3:c.227_229delGGAinsATT

Variant names:

• chr8-63073064-TCC-AAT
• rs1554524061
• NM_000370.3:c.227_229delGGAinsATT

Variant summary

Our verdict is Pathogenic. The variant received 16 ACMG points: 16P and 0B. PVS1 PP5_Very_Strong

The NM_000370.3(TTPA):​c.227_229delGGAinsATT​(p.TrpArg76*) variant causes a stop gained change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. It is difficult to determine the true allele frequency of this variant because it is of type MNV, and the frequency of such variant types in population databases may be underestimated and unreliable. Variant has been reported in ClinVar as Pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: not found (cov: 32)
• Consequence: TTPA NM_000370.3 stop_gained
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:4
• Conservation: PhyloP100: 7.23
• Publications: 0 publications found

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 Gene-Disease associations (from GenCC):

• familial isolated deficiency of vitamin E

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Orphanet, G2P, Myriad Women’s Health, Labcorp Genetics (formerly Invitae)

ACMG classification

Our verdict: Pathogenic. The variant received 16 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PP5: Variant 8-63073064-TCC-AAT is Pathogenic according to our data. Variant chr8-63073064-TCC-AAT is described in ClinVar as Pathogenic. ClinVar VariationId is 551293.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTPA	NM_000370.3	c.227_229delGGAinsATT	p.TrpArg76*	stop_gained		ENST00000260116.5	NP_000361.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTPA	ENST00000260116.5	c.227_229delGGAinsATT	p.TrpArg76*	stop_gained		1	NM_000370.3	ENSP00000260116.4
TTPA	ENST00000521138.1	n.232+12752_232+12754delGGAinsATT		intron_variant	Intron 1 of 1	5

Frequencies

GnomAD3 genomes Cov.: 32

We have no GnomAD4 exomes data on this position. Probably position not covered by the project.

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Familial isolated deficiency of vitamin E Pathogenic:3

Jan 16, 2024

Baylor Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Mar 29, 2017

Counsyl

Significance: Likely pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

This submission and the accompanying classification are no longer maintained by the submitter. For more information on current observations and classification, please contact variantquestions@myriad.com. -

Mar 16, 2024

Fulgent Genetics, Fulgent Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

not provided Pathogenic:1

Feb 05, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This premature translational stop signal has been observed in individual(s) with clinical features of ataxia with isolated vitamin E deficiency (PMID: 18458655). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. For these reasons, this variant has been classified as Pathogenic. ClinVar contains an entry for this variant (Variation ID: 551293). Information on the frequency of this variant in the gnomAD database is not available, as this variant may be reported differently in the database. This sequence change creates a premature translational stop signal (p.Trp76_Arg77delinsTyr*) 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). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
PhyloP100		7.2
Mutation Taster		=1/199	disease causing (fs/PTC)

Splicing

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

Other links and lift over

dbSNP: rs1554524061; hg19: chr8-63985623;