Genetic Variant TTPA:c.205-1G>A (chr8-63073089-C-T) – ACMG Classification: Pathogenic (10 pts)

Variant summary

Our verdict is Pathogenic. The variant received 10 ACMG points: 10P and 0B. PVS1PM2

The NM_000370.3(TTPA):c.205-1G>A variant causes a splice acceptor, intron change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000688 in 1,454,384 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar.

Frequency

Genomes: not found (cov: 32)

Exomes 𝑓: 6.9e-7 ( 0 hom. )

Consequence

TTPA
NM_000370.3 splice_acceptor, intron

Scores

Splicing: ADA: 1.000

Clinical Significance

Not reported in ClinVar

Conservation

PhyloP100: 7.23

Publications

1 publications found

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 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)

TTPA links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Pathogenic. The variant received 10 ACMG points.

PVS1

Splicing +-2 bp (donor or acceptor) variant, LoF is a know mechanism of disease, Cryptic splice site detected, with MaxEntScore 5.9, offset of -23, new splice context is: accatgtatgccatttgtAGaca. Cryptic site results in frameshift change. If cryptic site found is not functional and variant results in exon loss, it results in frameshift change.

PM2

Very rare variant in population databases, with high coverage;

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTPA	NM_000370.3 link	c.205-1G>A		splice_acceptor_variant, intron_variant	Intron 1 of 4	ENST00000260116.5	NP_000361.1	P49638

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTPA	ENST00000260116.5 link	c.205-1G>A		splice_acceptor_variant, intron_variant	Intron 1 of 4	1	NM_000370.3	ENSP00000260116.4		P49638
TTPA	ENST00000521138.1 link	n.232+12729G>A		intron_variant	Intron 1 of 1	5

Frequencies

GnomAD3 genomes

Cov.:

GnomAD2 exomes

AF:

0.00000403

AC:

AN:

248416

AF XY:

0.00000744

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.0000291

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:

6.88e-7

AC:

AN:

1454384

Hom.:

Cov.:

AF XY:

0.00000138

AC XY:

AN XY:

723890

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

33328

American (AMR)

AF:

0.0000224

AC:

AN:

44622

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26090

East Asian (EAS)

AF:

0.00

AC:

AN:

39624

South Asian (SAS)

AF:

0.00

AC:

AN:

85976

European-Finnish (FIN)

AF:

0.00

AC:

AN:

52516

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5480

European-Non Finnish (NFE)

AF:

0.00

AC:

AN:

1106602

Other (OTH)

AF:

0.00

AC:

AN:

60146

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.425

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_addAF

Pathogenic

0.57

BayesDel_noAF

Pathogenic

0.42

CADD

Pathogenic

(source)

DANN

Uncertain

1.0

Eigen

Pathogenic

1.2

Eigen_PC

Pathogenic

1.1

FATHMM_MKL

Pathogenic

1.0

PhyloP100

7.2

GERP RS

5.8

Mutation Taster

=0/100

disease causing

(source)

Splicing

Name

Calibrated prediction

Score

Prediction

dbscSNV1_ADA

Pathogenic

1.0

dbscSNV1_RF

Pathogenic

0.94

SpliceAI score (max)

0.94

Details are displayed if max score is > 0.2

DS_AL_spliceai

0.94

Position offset: -1

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