Genetic Variant TTC8:p.Asp65Val (chr14-88839501-A-T) – ACMG Classification: Likely_pathogenic (6 pts)

Variant summary

Our verdict is Likely pathogenic. The variant received 6 ACMG points: 6P and 0B. PM2PP3_Strong

The NM_144596.4(TTC8):c.194A>T(p.Asp65Val) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,068 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. D65G) has been classified as Likely benign.

Frequency

Genomes: not found (cov: 32)

Exomes 𝑓: 6.8e-7 ( 0 hom. )

Consequence

TTC8
NM_144596.4 missense

Scores

Clinical Significance

Not reported in ClinVar

Conservation

PhyloP100: 8.83

Publications

6 publications found

Variant links:

Genes affected

TTC8 (HGNC:20087): (tetratricopeptide repeat domain 8) This gene encodes a protein that has been directly linked to Bardet-Biedl syndrome. The primary features of this syndrome include retinal dystrophy, obesity, polydactyly, renal abnormalities and learning disabilities. Experimentation in non-human eukaryotes suggests that this gene is expressed in ciliated cells and that it is involved in the formation of cilia. A mutation in this gene has also been implicated in nonsyndromic retinitis pigmentosa. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Jan 2014]

TTC8 Gene-Disease associations (from GenCC):

Bardet-Biedl syndrome 8
Inheritance: AR Classification: DEFINITIVE, STRONG, MODERATE Submitted by: Genomics England PanelApp, Ambry Genetics, Labcorp Genetics (formerly Invitae), G2P
retinitis pigmentosa 51
Inheritance: AR Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), G2P
retinitis pigmentosa
Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
Bardet-Biedl syndrome
Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

TTC8 links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Likely_pathogenic. The variant received 6 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

PP3

MetaRNN computational evidence supports a deleterious effect, 0.966

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTC8	NM_144596.4 link	c.194A>T	p.Asp65Val	missense_variant	Exon 3 of 15	ENST00000380656.7	NP_653197.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTC8	ENST00000380656.7 link	c.194A>T	p.Asp65Val	missense_variant	Exon 3 of 15	2	NM_144596.4	ENSP00000370031.2

Frequencies

GnomAD3 genomes

Cov.:

GnomAD2 exomes

AF:

0.00000398

AC:

AN:

251200

AF XY:

0.00000737

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 FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00000881

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

6.84e-7

AC:

AN:

1461068

Hom.:

Cov.:

AF XY:

0.00000138

AC XY:

AN XY:

726860

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

33446

American (AMR)

AF:

0.00

AC:

AN:

44696

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26100

East Asian (EAS)

AF:

0.00

AC:

AN:

39538

South Asian (SAS)

AF:

0.00

AC:

AN:

86246

European-Finnish (FIN)

AF:

0.00

AC:

AN:

53398

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5760

European-Non Finnish (NFE)

AF:

9.00e-7

AC:

AN:

1111536

Other (OTH)

AF:

0.00

AC:

AN:

60348

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

GnomAD4 genome

Cov.:

ExAC

AF:

0.00000824

AC:

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Pathogenic

0.97

BayesDel_addAF

Pathogenic

0.22

BayesDel_noAF

Uncertain

0.080

CADD

Pathogenic

(source)

DANN

Uncertain

0.99

DEOGEN2

Benign

0.40

T;D;.;.;T;D;.;.

Eigen

Uncertain

0.52

Eigen_PC

Uncertain

0.52

FATHMM_MKL

Pathogenic

0.99

LIST_S2

Pathogenic

0.98

D;D;D;D;.;.;.;D

M_CAP

Uncertain

0.11

MetaRNN

Pathogenic

0.97

D;D;D;D;D;D;D;D

MetaSVM

Uncertain

0.22

MutationAssessor

Benign

0.0

.;.;M;.;.;.;M;.

PhyloP100

8.8

PrimateAI

Uncertain

0.57

PROVEAN

Benign

0.0

.;.;.;.;D;D;D;D

REVEL

Benign

0.0

Sift

Pathogenic

0.0

.;.;.;.;D;D;D;D

Sift4G

Pathogenic

0.0010

D;D;D;D;D;D;D;D

Vest4

0.87

ClinPred

1.0

GERP RS

6.0

gMVP

0.90

Mutation Taster

=205/95

polymorphism

(source)

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

ClinVar

Computational scores

Splicing

Publications

Other links and lift over