chr14-88824750-T-C

Position:

• chr14-88824750-T-C

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 2P and 1B. PM2 BP4

The NM_144596.4(TTC8):​c.43T>C​(p.Phe15Leu) variant causes a missense change. The variant allele was found at a frequency of 0.0000031 in 1,612,804 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency:
  • Genomes: 𝑓 0.000020 (0 hom., cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: TTC8 NM_144596.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 5.55

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 (HGNC:):

ACMG classification

Verdict is Uncertain_significance. Variant got 1 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.3992206).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TTC8	NM_144596.4	c.43T>C	p.Phe15Leu	missense_variant	1/15	ENST00000380656.7	NP_653197.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TTC8	ENST00000380656.7	c.43T>C	p.Phe15Leu	missense_variant	1/15	2	NM_144596.4	ENSP00000370031.2

Frequencies

GnomAD3 genomes AF: 0.0000197 AC: 3 AN: 152080 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000724

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: 0.00

Gnomad OTH AF: 0.00

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1460724 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 726516

Gnomad4 AFR exome AF: 0.0000598

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.0000197 AC: 3 AN: 152080 Hom.: 0 Cov.: 32 AF XY: 0.0000135 AC XY: 1 AN XY: 74290

Gnomad4 AFR AF: 0.0000724

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: 0.00

Gnomad4 OTH AF: 0.00

Bravo AF: 0.0000189

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Bardet-Biedl syndrome 8;C3150715:Retinitis pigmentosa 51 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Fulgent Genetics, Fulgent Genetics

Sep 21, 2021

- -

Bardet-Biedl syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

May 11, 2022

Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be tolerated. 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. This variant has not been reported in the literature in individuals affected with TTC8-related conditions. This sequence change replaces phenylalanine, which is neutral and non-polar, with leucine, which is neutral and non-polar, at codon 15 of the TTC8 protein (p.Phe15Leu). This variant is not present in population databases (gnomAD no frequency). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Uncertain	0.11	D
BayesDel_noAF	Uncertain	-0.080
CADD	Uncertain	23
DANN	Uncertain	1.0
DEOGEN2	Benign	0.20	T;T;.;.;T;T;.;.;.
Eigen	Uncertain	0.26
Eigen_PC	Uncertain	0.37
FATHMM_MKL	Uncertain	0.80	D
LIST_S2	Uncertain	0.90	D;D;D;D;.;.;D;.;D
M_CAP	Benign	0.077	D
MetaRNN	Benign	0.40	T;T;T;T;T;T;T;T;T
MetaSVM	Uncertain	-0.21	T
MutationAssessor	Benign	1.8	.;.;L;.;.;.;L;L;.
MutationTaster	Benign	1.0	D;D;D;D;D;N
PrimateAI	Uncertain	0.74	T
PROVEAN	Uncertain	-3.3	.;.;D;.;D;D;N;D;D
REVEL	Benign	0.13
Sift	Benign	0.14	.;.;T;.;T;T;T;T;T
Sift4G	Benign	0.44	T;T;T;T;T;T;T;T;T
Polyphen		0.0040, 0.97, 0.94	.;.;B;.;.;.;D;B;P
Vest4		0.54
MutPred		0.44		Gain of disorder (P = 0.0874);Gain of disorder (P = 0.0874);Gain of disorder (P = 0.0874);Gain of disorder (P = 0.0874);Gain of disorder (P = 0.0874);Gain of disorder (P = 0.0874);Gain of disorder (P = 0.0874);Gain of disorder (P = 0.0874);Gain of disorder (P = 0.0874);
MVP		0.81
MPC		0.55
ClinPred		0.99	D
GERP RS		5.5
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		2.6
gMVP		0.68

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

Other links and lift over

dbSNP: rs1379428942; hg19: chr14-89291094;