Genetic Variant TTC8:n.-25G>C (chr14-88824683-G-C) – ACMG Classification: Likely_benign (-2 pts)

Variant summary

Our verdict is Likely benign. The variant received -2 ACMG points: 2P and 4B. PM2BP4_Strong

The ENST00000555057.5(TTC8):n.-25G>C variant causes a non coding transcript exon change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000657 in 152,102 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar.

Frequency

Genomes: 𝑓 0.0000066 ( 0 hom., cov: 32)

Exomes 𝑓: 0.0 ( 0 hom. )

Failed GnomAD Quality Control

Consequence

TTC8
ENST00000555057.5 non_coding_transcript_exon

Scores

Clinical Significance

Not reported in ClinVar

Conservation

PhyloP100: -1.29

Publications

2 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_benign. The variant received -2 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

BP4

Computational evidence support a benign effect (BayesDel_noAF=-0.84).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTC8	NM_144596.4 link	c.-25G>C		5_prime_UTR_variant	Exon 1 of 15	ENST00000380656.7	NP_653197.2	Q8TAM2-4Q86U25

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTC8	ENST00000380656.7 link	c.-25G>C		5_prime_UTR_variant	Exon 1 of 15	2	NM_144596.4	ENSP00000370031.2		Q8TAM2-4

Frequencies

GnomAD3 genomes

AF:

0.00000657

AC:

AN:

152102

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:

0.00

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

GnomAD4 exome

Data not reliable, filtered out with message: AC0

AF:

0.00

AC:

AN:

1419160

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

703706

African (AFR)

AF:

0.00

AC:

AN:

32628

American (AMR)

AF:

0.00

AC:

AN:

39948

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

25446

East Asian (EAS)

AF:

0.00

AC:

AN:

38088

South Asian (SAS)

AF:

0.00

AC:

AN:

82038

European-Finnish (FIN)

AF:

0.00

AC:

AN:

50172

Middle Eastern (MID)

AF:

0.00

AC:

AN:

4750

European-Non Finnish (NFE)

AF:

0.00

AC:

AN:

1087374

Other (OTH)

AF:

0.00

AC:

AN:

58716

GnomAD4 genome

AF:

0.00000657

AC:

AN:

152102

Hom.:

Cov.:

AF XY:

0.0000135

AC XY:

AN XY:

74292

show subpopulations

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5.

African (AFR)

AF:

0.00

AC:

AN:

41422

American (AMR)

AF:

0.00

AC:

AN:

15278

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3466

East Asian (EAS)

AF:

0.00

AC:

AN:

5158

South Asian (SAS)

AF:

0.00

AC:

AN:

4832

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10612

Middle Eastern (MID)

AF:

0.00

AC:

AN:

316

European-Non Finnish (NFE)

AF:

0.0000147

AC:

AN:

68012

Other (OTH)

AF:

0.00

AC:

AN:

2094

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5. (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.275

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Genome 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

Alfa

AF:

0.00

Hom.:

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_noAF

Benign

-0.84

CADD

Benign

2.3

(source)

DANN

Benign

0.68

PhyloP100

-1.3

PromoterAI

-0.41

Neutral

(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

Age Distribution

ClinVar

Computational scores

Splicing

Publications

Other links and lift over