rs866222900

chr2-165924570-C-T

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PM2 PP3_Moderate

The NM_024753.5(TTC21B):c.1495G>A(p.Ala499Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000248 in 1,613,316 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 0.000013 (0 hom., cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: TTC21B NM_024753.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts P:2 U:2
• Conservation: PhyloP100: 7.45

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]

ACMG classification

Verdict is Uncertain_significance. Variant got 4 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.856

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TTC21B	NM_024753.5	c.1495G>A	p.Ala499Thr	missense_variant	12/29	ENST00000243344.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TTC21B	ENST00000243344.8	c.1495G>A	p.Ala499Thr	missense_variant	12/29	1	NM_024753.5	P1

Frequencies

GnomAD3 genomes AF: 0.0000132 AC: 2 AN: 152046 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000483

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: 1461270 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 726936

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: 0.0000132 AC: 2 AN: 152046 Hom.: 0 Cov.: 32 AF XY: 0.0000269 AC XY: 2 AN XY: 74254

Gnomad4 AFR AF: 0.0000483

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: 0.0000264

ClinVar

Significance: Uncertain significance

Submissions summary: Pathogenic:2 Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Jeune thoracic dystrophy Pathogenic:2

Likely pathogenic, no assertion criteria provided	research	University of Washington Center for Mendelian Genomics, University of Washington	-	- -
Likely pathogenic, no assertion criteria provided	research	Dan Cohn Lab, University Of California Los Angeles	Jun 01, 2017	- -

Jeune thoracic dystrophy;C0687120:Nephronophthisis Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Feb 16, 2022

This sequence change replaces alanine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 499 of the TTC21B protein (p.Ala499Thr). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with short-rib thoracic dysplasia (PMID: 29068549). ClinVar contains an entry for this variant (Variation ID: 432560). 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 disruptive. 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. -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

GeneDx

Jun 26, 2017

A variant of uncertain significance has been identified in the TTC21B gene. The A499T variant has not been published as a pathogenic variant, nor has it been reported as a benign variant to our knowledge. The A499T variant is not observed in large population cohorts (Lek et al., 2016; 1000 Genomes Consortium et al., 2015; Exome Variant Server). The A499T 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, and in silico analysis predicts this variant is probably damaging to the protein structure/function. Based on the currently available information, it is unclear whether this variant is a pathogenic variant or a rare benign variant. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.57
BayesDel_addAF	Pathogenic	0.42	D
BayesDel_noAF	Pathogenic	0.37
Cadd	Pathogenic	26
Dann	Pathogenic	1.0
DEOGEN2	Uncertain	0.63	D
Eigen	Pathogenic	0.90
Eigen_PC	Pathogenic	0.87
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.92	D
M_CAP	Uncertain	0.13	D
MetaRNN	Pathogenic	0.86	D
MetaSVM	Uncertain	0.64	D
MutationAssessor	Pathogenic	3.0	M
MutationTaster	Benign	1.0	D
PrimateAI	Uncertain	0.64	T
PROVEAN	Uncertain	-3.5	D
REVEL	Pathogenic	0.84
Sift	Uncertain	0.0020	D
Sift4G	Uncertain	0.0040	D
Polyphen		1.0	D
Vest4		0.79
MutPred		0.52		Loss of ubiquitination at K500 (P = 0.1231);
MVP		0.66
MPC		0.21
ClinPred		0.98	D
GERP RS		5.8
Varity_R		0.64
gMVP		0.65

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: rs866222900; hg19: chr2-166781080;