2-165941139-T-C

Position:

• chr2-165941139-T-C

Variant summary

Our verdict is Uncertain significance. Variant got 0 ACMG points: 2P and 2B. PM2 BP4_Moderate

The NM_024753.5(TTC21B):​c.598A>G​(p.Thr200Ala) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,461,642 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 14/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: TTC21B NM_024753.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 1.15

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 (HGNC:):

ACMG classification

Verdict is Uncertain_significance. Variant got 0 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.10367647).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TTC21B	NM_024753.5	c.598A>G	p.Thr200Ala	missense_variant	6/29	ENST00000243344.8	NP_079029.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TTC21B	ENST00000243344.8	c.598A>G	p.Thr200Ala	missense_variant	6/29	1	NM_024753.5	ENSP00000243344.7

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461642 Hom.: 0 Cov.: 33 AF XY: 0.00 AC XY: 0 AN XY: 727124

Gnomad4 AFR exome AF: 0.00

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: 8.99e-7

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Jeune thoracic dystrophy;C0687120:Nephronophthisis Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Oct 24, 2022

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. 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) performed at Invitae indicates that this missense variant is not expected to disrupt TTC21B protein function. ClinVar contains an entry for this variant (Variation ID: 1381203). This variant has not been reported in the literature in individuals affected with TTC21B-related conditions. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces threonine, which is neutral and polar, with alanine, which is neutral and non-polar, at codon 200 of the TTC21B protein (p.Thr200Ala). -

Inborn genetic diseases Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Jan 30, 2024

The c.598A>G (p.T200A) alteration is located in exon 6 (coding exon 6) of the TTC21B gene. This alteration results from a A to G substitution at nucleotide position 598, causing the threonine (T) at amino acid position 200 to be replaced by an alanine (A). Based on insufficient or conflicting evidence, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.084
BayesDel_addAF	Benign	-0.24	T
BayesDel_noAF	Benign	-0.58
CADD	Benign	15
DANN	Uncertain	0.98
DEOGEN2	Benign	0.079	T
Eigen	Benign	-0.31
Eigen_PC	Benign	-0.16
FATHMM_MKL	Uncertain	0.88	D
LIST_S2	Benign	0.59	T
M_CAP	Benign	0.0096	T
MetaRNN	Benign	0.10	T
MetaSVM	Benign	-1.1	T
MutationAssessor	Benign	1.9	L
PrimateAI	Benign	0.38	T
PROVEAN	Benign	-0.71	N
REVEL	Benign	0.027
Sift	Benign	0.061	T
Sift4G	Benign	0.063	T
Polyphen		0.0020	B
Vest4		0.10
MutPred		0.51		Gain of glycosylation at S195 (P = 0.1795);
MVP		0.19
MPC		0.030
ClinPred		0.15	T
GERP RS		3.0
Varity_R		0.035
gMVP		0.20

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.040		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: rs1387736357; hg19: chr2-166797649;