NM_024753.5:c.3223G>C

Variant names:

Variant summary

Our verdict is Likely benign. The variant received -4 ACMG points: 0P and 4B. BP4_Strong

The NM_024753.5(TTC21B):c.3223G>C(p.Val1075Leu) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000351 in 1,613,598 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 17/22 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

Frequency

Genomes: 𝑓 0.00033 ( 0 hom., cov: 32)

Exomes 𝑓: 0.00035 ( 0 hom. )

Consequence

TTC21B
NM_024753.5 missense

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:5B:1

Conservation

PhyloP100: -0.449

Publications

2 publications found

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 Gene-Disease associations (from GenCC):

nephronophthisis 12
Inheritance: AD, AR Classification: DEFINITIVE, STRONG, LIMITED Submitted by: Ambry Genetics, ClinGen, Labcorp Genetics (formerly Invitae)
asphyxiating thoracic dystrophy 4
Inheritance: AR Classification: DEFINITIVE, STRONG Submitted by: Ambry Genetics, Labcorp Genetics (formerly Invitae)
Jeune syndrome
Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
nephronophthisis 2
Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

TTC21B links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Likely_benign. The variant received -4 ACMG points.

BP4

Computational evidence support a benign effect (MetaRNN=0.016611248).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein
TTC21B	NM_024753.5 link	c.3223G>C	p.Val1075Leu	missense_variant	Exon 24 of 29	ENST00000243344.8	NP_079029.3
TTC21B	XM_017004967.2 link	c.3223G>C	p.Val1075Leu	missense_variant	Exon 24 of 28		XP_016860456.1
TTC21B	XM_047445870.1 link	c.2569G>C	p.Val857Leu	missense_variant	Exon 20 of 25		XP_047301826.1
TTC21B	XM_011511871.4 link	c.2473G>C	p.Val825Leu	missense_variant	Exon 19 of 24		XP_011510173.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTC21B	ENST00000243344.8 link	c.3223G>C	p.Val1075Leu	missense_variant	Exon 24 of 29	1	NM_024753.5	ENSP00000243344.7

Frequencies

GnomAD3 genomes

AF:

0.000329

AC:

AN:

152128

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000483

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.000327

Gnomad ASJ

AF:

0.00115

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.000544

Gnomad OTH

AF:

0.000955

GnomAD2 exomes

AF:

0.000323

AC:

AN:

250700

AF XY:

0.000347

show subpopulations

Gnomad AFR exome

AF:

0.0000616

Gnomad AMR exome

AF:

0.0000579

Gnomad ASJ exome

AF:

0.000894

Gnomad EAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.0000463

Gnomad NFE exome

AF:

0.000583

Gnomad OTH exome

AF:

0.000327

GnomAD4 exome

AF:

0.000353

AC:

516

AN:

1461352

Hom.:

Cov.:

AF XY:

0.000347

AC XY:

252

AN XY:

726972

show subpopulations

African (AFR)

AF:

0.000179

AC:

AN:

33450

American (AMR)

AF:

0.0000671

AC:

AN:

44704

Ashkenazi Jewish (ASJ)

AF:

0.00149

AC:

AN:

26122

East Asian (EAS)

AF:

0.00

AC:

AN:

39626

South Asian (SAS)

AF:

0.00

AC:

AN:

86236

European-Finnish (FIN)

AF:

0.0000375

AC:

AN:

53392

Middle Eastern (MID)

AF:

0.000173

AC:

AN:

5764

European-Non Finnish (NFE)

AF:

0.000397

AC:

441

AN:

1111694

Other (OTH)

AF:

0.000398

AC:

AN:

60364

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.466

Heterozygous variant carriers

123

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome Het

Variant carriers

100

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

GnomAD4 genome

AF:

0.000328

AC:

AN:

152246

Hom.:

Cov.:

AF XY:

0.000322

AC XY:

AN XY:

74448

show subpopulations

African (AFR)

AF:

0.0000481

AC:

AN:

41556

American (AMR)

AF:

0.000327

AC:

AN:

15300

Ashkenazi Jewish (ASJ)

AF:

0.00115

AC:

AN:

3470

East Asian (EAS)

AF:

0.00

AC:

AN:

5182

South Asian (SAS)

AF:

0.00

AC:

AN:

4826

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10612

Middle Eastern (MID)

AF:

0.00

AC:

AN:

294

European-Non Finnish (NFE)

AF:

0.000544

AC:

AN:

67980

Other (OTH)

AF:

0.000945

AC:

AN:

2116

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.494

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:

0.000625

Hom.:

Bravo

AF:

0.000340

ESP6500AA

AF:

0.00

AC:

ESP6500EA

AF:

0.000582

AC:

ExAC

AF:

0.000321

AC:

EpiCase

AF:

0.000763

EpiControl

AF:

0.000533

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:5Benign:1

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

Asphyxiating thoracic dystrophy 4;C3151186:Nephronophthisis 12

Uncertain:1

Mar 03, 2022

Fulgent Genetics, Fulgent Genetics

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Asphyxiating thoracic dystrophy 4

Uncertain:1

Jan 12, 2018

Illumina Laboratory Services, Illumina

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease.

Nephronophthisis 12

Uncertain:1

Jan 12, 2018

Illumina Laboratory Services, Illumina

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

not provided

Uncertain:1

Nov 29, 2021

GeneDx

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

In silico analysis supports that this missense variant does not alter protein structure/function; Has not been previously published as pathogenic or benign to our knowledge

TTC21B-related disorder

Uncertain:1

Jul 24, 2024

PreventionGenetics, part of Exact Sciences

Significance:Uncertain significance

Review Status:no assertion criteria provided

Collection Method:clinical testing

The TTC21B c.3223G>C variant is predicted to result in the amino acid substitution p.Val1075Leu. To our knowledge, this variant has not been reported in the literature. This variant is reported in 0.087% of alleles in individuals of Ashkenazi Jewish descent in gnomAD, which may be too frequent to be an unreported primary cause of disease. Although we suspect that c.3223G>C (p.Val1075Leu) may be benign, the clinical significance of this variant is currently classified as uncertain due to the absence of conclusive functional and genetic evidence.

Jeune thoracic dystrophy;C0687120:Nephronophthisis

Benign:1

Jan 30, 2025

Labcorp Genetics (formerly Invitae), Labcorp

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.11

BayesDel_addAF

Benign

-0.46

BayesDel_noAF

Benign

-0.54

CADD

Benign

0.43

(source)

DANN

Benign

0.78

DEOGEN2

Benign

0.068

Eigen

Benign

-1.3

Eigen_PC

Benign

-1.3

FATHMM_MKL

Benign

0.12

LIST_S2

Benign

0.85

M_CAP

Benign

0.019

MetaRNN

Benign

0.017

MetaSVM

Benign

-1.0

MutationAssessor

Benign

1.0

PhyloP100

-0.45

PrimateAI

Benign

0.28

PROVEAN

Benign

-0.89

REVEL

Benign

0.095

Sift

Benign

0.42

Sift4G

Benign

0.61

Vest4

0.26

ClinPred

0.012

GERP RS

-5.7

RBP_binding_hub_radar

0.0

RBP_regulation_power_radar

1.1

Varity_R

0.079

gMVP

0.12

Mutation Taster

=88/12

polymorphism

(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

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over