Genetic Variant TTC21B:p.Ala235Pro (chr2-165941034-C-G) – ACMG Classification: Uncertain_significance (3 pts)

Variant summary

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

The NM_024753.5(TTC21B):c.703G>C(p.Ala235Pro) variant causes a missense change. The variant allele was found at a frequency of 0.0000062 in 1,613,670 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

Frequency

Genomes: 𝑓 0.000053 ( 0 hom., cov: 33)

Exomes 𝑓: 0.0000014 ( 0 hom. )

Consequence

TTC21B
NM_024753.5 missense

Scores

Clinical Significance

Uncertain significance criteria provided, multiple submitters, no conflicts P:2U:3

Conservation

PhyloP100: 6.11

Variant links:

Genes affected

TTC21B (HGNC:25660): (tetratricopeptide repeat domain 21B) This gene encodes a member of TTC21 family, containing several tetratricopeptide repeat (TPR) domains. This protein is localized to the cilium axoneme, and may play a role in retrograde intraflagellar transport in cilia. Mutations in this gene are associated with various ciliopathies, nephronophthisis 12, and asphyxiating thoracic dystrophy 4. [provided by RefSeq, Oct 2011]

TTC21B links:

TTC21B-AS1 (HGNC:41115): (TTC21B antisense RNA 1)

TTC21B-AS1 links:

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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

MetaRNN computational evidence supports a deleterious effect, 0.805

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTC21B	NM_024753.5 link	c.703G>C	p.Ala235Pro	missense_variant	Exon 6 of 29	ENST00000243344.8	NP_079029.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTC21B	ENST00000243344.8 link	c.703G>C	p.Ala235Pro	missense_variant	Exon 6 of 29	1	NM_024753.5	ENSP00000243344.7		Q7Z4L5-1

Frequencies

GnomAD3 genomes

AF:

0.0000526

AC:

AN:

152176

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.000193

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:

AN:

1461494

Hom.:

Cov.:

AF XY:

0.00000138

AC XY:

AN XY:

727040

show subpopulations

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:

0.0000526

AC:

AN:

152176

Hom.:

Cov.:

AF XY:

0.0000538

AC XY:

AN XY:

74352

show subpopulations

Gnomad4 AFR

AF:

0.000193

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

Alfa

AF:

0.0000712

Hom.:

Bravo

AF:

0.0000491

ESP6500AA

AF:

0.000227

AC:

ESP6500EA

AF:

0.00

AC:

ExAC

AF:

0.00000824

AC:

ClinVar

Significance: Uncertain significance

Submissions summary: Pathogenic:2Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

Jeune thoracic dystrophy

Pathogenic:2

Jun 01, 2017

Dan Cohn Lab, University Of California Los Angeles

Significance: Likely pathogenic

Review Status: no assertion criteria provided

Collection Method: research

- -

University of Washington Center for Mendelian Genomics, University of Washington

Significance: Likely pathogenic

Review Status: no assertion criteria provided

Collection Method: research

- -

Asphyxiating thoracic dystrophy 4;C3151186:Nephronophthisis 12

Uncertain:1

May 23, 2024

Fulgent Genetics, Fulgent Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Jeune thoracic dystrophy;C0687120:Nephronophthisis

Uncertain:1

Nov 13, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces alanine, which is neutral and non-polar, with proline, which is neutral and non-polar, at codon 235 of the TTC21B protein (p.Ala235Pro). This variant is present in population databases (rs150742619, gnomAD 0.02%). This missense change has been observed in individual(s) with asphyxiating thoracic dystrophy (PMID: 29068549). ClinVar contains an entry for this variant (Variation ID: 446647). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) has been performed at Invitae for this missense variant, however the output from this modeling did not meet the statistical confidence thresholds required to predict the impact of this variant on TTC21B protein function. 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. -

TTC21B-related disorder

Uncertain:1

Aug 26, 2024

PreventionGenetics, part of Exact Sciences

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: clinical testing

The TTC21B c.703G>C variant is predicted to result in the amino acid substitution p.Ala235Pro. This variant was reported in addition to two other variants in this gene in an individual with short rib polydactyly syndrome (Table S2, Zhang et al 2018. PubMed ID: 29068549). This variant is reported in 0.023% 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. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Pathogenic

0.95

BayesDel_addAF

Pathogenic

0.25

BayesDel_noAF

Uncertain

0.13

CADD

Pathogenic

DANN

Uncertain

1.0

DEOGEN2

Uncertain

0.62

Eigen

Uncertain

0.48

Eigen_PC

Uncertain

0.43

FATHMM_MKL

Pathogenic

1.0

LIST_S2

Uncertain

0.94

M_CAP

Benign

0.058

MetaRNN

Pathogenic

0.81

MetaSVM

Benign

-0.33

MutationAssessor

Uncertain

2.9

PrimateAI

Uncertain

0.56

PROVEAN

Uncertain

-3.0

REVEL

Uncertain

0.44

Sift

Uncertain

0.018

Sift4G

Uncertain

0.054

Polyphen

0.96

Vest4

0.89

MVP

0.35

MPC

0.23

ClinPred

0.98

GERP RS

4.3

RBP_binding_hub_radar

0.0

RBP_regulation_power_radar

1.1

Varity_R

0.72

gMVP

0.84

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