rs755412340

Positions:

chr14-88871550-C-T

Variant summary

Our verdict is Uncertain significance. Variant got 3 ACMG points: 3P and 0B. PM2PP3

The NM_144596.4(TTC8):c.1051C>T(p.Arg351Trp) variant causes a missense, splice region change. The variant allele was found at a frequency of 0.0000118 in 1,613,394 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 2/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Uncertain significance (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R351Q) has been classified as Uncertain significance.

Frequency

Genomes: 𝑓 0.000053 ( 0 hom., cov: 32)

Exomes 𝑓: 0.0000075 ( 0 hom. )

Consequence

TTC8
NM_144596.4 missense, splice_region

Scores

Splicing: ADA: 0.9715

Clinical Significance

Uncertain significance criteria provided, multiple submitters, no conflicts U:5

Conservation

PhyloP100: 5.78

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 links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Uncertain_significance. Variant got 3 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

PP3

Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF. No scorers claiming Uncertain. Scorers claiming Benign: max_spliceai.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TTC8	NM_144596.4 linkuse as main transcript	c.1051C>T	p.Arg351Trp	missense_variant, splice_region_variant	12/15	ENST00000380656.7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TTC8	ENST00000380656.7 linkuse as main transcript	c.1051C>T	p.Arg351Trp	missense_variant, splice_region_variant	12/15	2	NM_144596.4		Q8TAM2-4

Frequencies

GnomAD3 genomes

AF:

0.0000527

AC:

AN:

151946

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.000169

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:

0.0000147

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.0000159

AC:

AN:

250898

Hom.:

AF XY:

0.00000737

AC XY:

AN XY:

135630

show subpopulations

Gnomad AFR exome

AF:

0.000185

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.0000545

Gnomad SAS 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:

0.00000753

AC:

AN:

1461448

Hom.:

Cov.:

AF XY:

0.00000825

AC XY:

AN XY:

727052

show subpopulations

Gnomad4 AFR exome

AF:

0.0000299

Gnomad4 AMR exome

AF:

0.00

Gnomad4 ASJ exome

AF:

0.00

Gnomad4 EAS exome

AF:

0.0000504

Gnomad4 SAS exome

AF:

0.00

Gnomad4 FIN exome

AF:

0.00

Gnomad4 NFE exome

AF:

0.00000630

Gnomad4 OTH exome

AF:

0.0000166

GnomAD4 genome

AF:

0.0000527

AC:

AN:

151946

Hom.:

Cov.:

AF XY:

0.0000539

AC XY:

AN XY:

74182

show subpopulations

Gnomad4 AFR

AF:

0.000169

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:

0.0000147

Gnomad4 OTH

AF:

0.00

Bravo

AF:

0.0000453

ExAC

AF:

0.0000330

AC:

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:5

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

Bardet-Biedl syndrome 8

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

New York Genome Center

Oct 24, 2022

- -

Bardet-Biedl syndrome 8;C3150715:Retinitis pigmentosa 51

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Fulgent Genetics, Fulgent Genetics

Apr 22, 2022

- -

TTC8-related disorder

Uncertain:1

Uncertain significance, no assertion criteria provided

clinical testing

PreventionGenetics, part of Exact Sciences

Sep 17, 2024

The TTC8 c.1051C>T variant is predicted to result in the amino acid substitution p.Arg351Trp. To our knowledge, this variant has not been reported in the literature. This variant is reported in 0.020% of alleles in individuals of African descent in gnomAD. At this time, the clinical significance of this variant is uncertain due to the absence of conclusive functional and genetic evidence. -

not provided

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

GeneDx

Feb 03, 2017

The R341W variant in the TTC8 gene has not been reported previously as a pathogenic variant, nor as a benign variant, to our knowledge. The R341W variant is not observed at a significant frequency in large population cohorts (Lek et al., 2016; 1000 Genomes Consortium et al., 2015; Exome Variant Server). The R341W variant is a non-conservative amino acid substitution, which is likely to impact secondary protein structure as these residues differ in polarity, charge, size and/or other properties. This substitution occurs at a position that is conserved across species. In silico analysis predicts this variant is probably damaging to the protein structure/function. We interpret R341W as a variant of uncertain significance. -

Bardet-Biedl syndrome

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Sep 01, 2021

This sequence change replaces arginine with tryptophan at codon 341 of the TTC8 protein (p.Arg341Trp). The arginine residue is highly conserved and there is a moderate physicochemical difference between arginine and tryptophan. This variant is present in population databases (rs755412340, ExAC 0.03%). This variant has not been reported in the literature in individuals affected with TTC8-related conditions. ClinVar contains an entry for this variant (Variation ID: 423070). Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_addAF

Uncertain

0.12

BayesDel_noAF

Pathogenic

0.22

CADD

Pathogenic

DANN

Pathogenic

1.0

DEOGEN2

Uncertain

0.55

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

Eigen

Pathogenic

0.82

Eigen_PC

Pathogenic

0.78

FATHMM_MKL

Pathogenic

0.99

LIST_S2

Pathogenic

0.98

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

M_CAP

Uncertain

0.095

MetaRNN

Pathogenic

0.83

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

MetaSVM

Uncertain

-0.19

MutationTaster

Benign

1.0

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

PrimateAI

Pathogenic

0.84

PROVEAN

Pathogenic

-7.9

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

REVEL

Uncertain

0.49

Sift

Pathogenic

0.0

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

Sift4G

Pathogenic

0.0

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

Polyphen

1.0

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

Vest4

0.80

MVP

0.79

MPC

0.54

ClinPred

1.0

GERP RS

4.8

gMVP

0.79

Splicing

Name

Calibrated prediction

Score

Prediction

dbscSNV1_ADA

Pathogenic

0.97

dbscSNV1_RF

Pathogenic

0.72

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