2-165901797-A-T

Variant names:

• chr2-165901797-A-T
• NM_024753.5:c.2682T>A
• TTC21B p.Ser894Ser

Variant summary

Our verdict is Likely benign. The variant received -3 ACMG points: 2P and 5B. PM2 BP4_Strong BP7

The NM_024753.5(TTC21B):​c.2682T>A​(p.Ser894Ser) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Synonymous variant affecting the same amino acid position (i.e. S894S) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 32)
• Consequence: TTC21B NM_024753.5 synonymous
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 1.14
• Publications: 0 publications found

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):

• asphyxiating thoracic dystrophy 4

  Inheritance: AR Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), Ambry Genetics
• nephronophthisis 12

  Inheritance: AR, AD Classification: DEFINITIVE, STRONG, LIMITED Submitted by: Labcorp Genetics (formerly Invitae), ClinGen, Ambry Genetics
• Jeune syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• nephronophthisis 2

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Likely_benign. The variant received -3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.54).
• BP7: Synonymous conserved (PhyloP=1.13 with no splicing effect.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_024753.5. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TTC21B	NM_024753.5	MANE Select	c.2682T>A	p.Ser894Ser	synonymous	Exon 20 of 29	NP_079029.3

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TTC21B	ENST00000243344.8	TSL:1 MANE Select	c.2682T>A	p.Ser894Ser	synonymous	Exon 20 of 29	ENSP00000243344.7	Q7Z4L5-1
	TTC21B	ENST00000679840.1		c.2682T>A	p.Ser894Ser	synonymous	Exon 20 of 27	ENSP00000505248.1	A0A7P0T8P4
	TTC21B	ENST00000679799.1		c.2682T>A	p.Ser894Ser	synonymous	Exon 20 of 28	ENSP00000505208.1	A0A494C0N4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.54
CADD	Benign	8.1
DANN	Benign	0.72
PhyloP100		1.1
Mutation Taster		=100/0	polymorphism

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

MaxEntScan Visualizer can be used to analyze the impact of this mutation on the neighboring sequence.

Other links and lift over

hg19: chr2-166758307;