14-88824712-G-A

Position:

chr14-88824712-G-A

Variant summary

Our verdict is Likely benign. Variant got -3 ACMG points: 2P and 5B. PM2BP4_StrongBS1_Supporting

The NM_144596.4(TTC8):c.5G>A(p.Ser2Asn) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000398 in 1,607,368 control chromosomes in the GnomAD database, including 1 homozygotes. In-silico tool predicts a benign outcome for this variant. 14/19 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

Frequency

Genomes: 𝑓 0.000033 ( 0 hom., cov: 32)

Exomes 𝑓: 0.000041 ( 1 hom. )

Consequence

TTC8
NM_144596.4 missense

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:4B:1

Conservation

PhyloP100: 0.317

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 Likely_benign. Variant got -3 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

BP4

Computational evidence support a benign effect (MetaRNN=0.014975786).

BS1

Variant frequency is greater than expected in population eas. gnomad4 allele frequency = 0.0000328 (5/152256) while in subpopulation EAS AF= 0.000971 (5/5148). AF 95% confidence interval is 0.000382. There are 0 homozygotes in gnomad4. There are 2 alleles in male gnomad4 subpopulation. Median coverage is 32. This position pass quality control queck. Existence of Clinvar submissions makes me limit the strength of this signal to Supporting

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TTC8	NM_144596.4 link	c.5G>A	p.Ser2Asn	missense_variant	1/15	ENST00000380656.7	NP_653197.2	Q8TAM2-4Q86U25

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TTC8	ENST00000380656.7 link	c.5G>A	p.Ser2Asn	missense_variant	1/15	2	NM_144596.4	ENSP00000370031.2		Q8TAM2-4

Frequencies

GnomAD3 genomes

AF:

0.0000329

AC:

AN:

152138

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.000969

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.00

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.0000768

AC:

AN:

234234

Hom.:

AF XY:

0.000101

AC XY:

AN XY:

128090

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.000983

Gnomad SAS exome

AF:

0.0000343

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.0000405

AC:

AN:

1455112

Hom.:

Cov.:

AF XY:

0.0000470

AC XY:

AN XY:

723280

show subpopulations

Gnomad4 AFR exome

AF:

0.00

Gnomad4 AMR exome

AF:

0.00

Gnomad4 ASJ exome

AF:

0.00

Gnomad4 EAS exome

AF:

0.00142

Gnomad4 SAS exome

AF:

0.0000118

Gnomad4 FIN exome

AF:

0.00

Gnomad4 NFE exome

AF:

9.01e-7

Gnomad4 OTH exome

AF:

0.0000166

GnomAD4 genome

AF:

0.0000328

AC:

AN:

152256

Hom.:

Cov.:

AF XY:

0.0000269

AC XY:

AN XY:

74438

show subpopulations

Gnomad4 AFR

AF:

0.00

Gnomad4 AMR

AF:

0.00

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.000971

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.00

Gnomad4 OTH

AF:

0.00

ExAC

AF:

0.0000989

AC:

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:4Benign:1

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

Bardet-Biedl syndrome 8

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 13, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Inborn genetic diseases

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Apr 09, 2024

The c.5G>A (p.S2N) alteration is located in exon 1 (coding exon 1) of the TTC8 gene. This alteration results from a G to A substitution at nucleotide position 5, causing the serine (S) at amino acid position 2 to be replaced by an asparagine (N). Based on insufficient or conflicting evidence, the clinical significance of this alteration remains unclear. -

Bardet-Biedl syndrome

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Aug 30, 2023

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. An algorithm developed to predict the effect of missense changes on protein structure and function (PolyPhen-2) suggests that this variant¬†is likely to be tolerated. ClinVar contains an entry for this variant (Variation ID: 314797). This variant has not been reported in the literature in individuals affected with TTC8-related conditions. This variant is present in population databases (rs199571677, gnomAD 0.09%). This sequence change replaces serine, which is neutral and polar, with asparagine, which is neutral and polar, at codon 2 of the TTC8 protein (p.Ser2Asn). -

Retinitis pigmentosa

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 13, 2018

Retinal dystrophy

Benign:1

Likely benign, criteria provided, single submitter

research

Dept Of Ophthalmology, Nagoya University

Oct 01, 2023

- -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_addAF

Benign

-0.42

BayesDel_noAF

Benign

-0.43

CADD

Benign

9.9

DANN

Uncertain

0.98

DEOGEN2

Benign

0.045

T;T;.;.;T;T;.;.;.

Eigen

Benign

-0.76

Eigen_PC

Benign

-0.67

FATHMM_MKL

Benign

0.22

LIST_S2

Benign

0.47

T;T;T;T;.;.;T;.;T

M_CAP

Benign

0.028

MetaRNN

Benign

0.015

T;T;T;T;T;T;T;T;T

MetaSVM

Benign

-0.94

MutationAssessor

Benign

0.69

.;.;N;.;.;.;N;N;.

PrimateAI

Benign

0.48

PROVEAN

Benign

-0.30

.;.;N;.;N;N;N;N;N

REVEL

Benign

0.15

Sift

Benign

0.27

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

Sift4G

Benign

0.58

T;T;T;T;T;T;D;T;T

Polyphen

0.0, 0.065

.;.;B;.;.;.;B;B;B

Vest4

0.088

MVP

0.59

MPC

0.10

ClinPred

0.048

GERP RS

0.070

RBP_binding_hub_radar

0.0

RBP_regulation_power_radar

1.6

gMVP

0.091

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