chr2-165953686-T-TCACCC

Variant names:

• chr2-165953686-T-TCACCC
• rs759648976
• NM_024753.5:c.19_20insGGGTG

Variant summary

Our verdict is Pathogenic. The variant received 10 ACMG points: 10P and 0B. PVS1 PM2

The NM_024753.5(TTC21B):​c.19_20insGGGTG​(p.Lys7ArgfsTer5) variant causes a frameshift, splice region change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000898 in 557,028 control chromosomes in the GnomAD database, with no homozygous occurrence. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar.

• Frequency:
  • Genomes: not found (cov: 26)
  • Exomes 𝑓: 0.0000090 (0 hom.)
• Consequence: TTC21B NM_024753.5 frameshift, splice_region
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 0.359
• 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: Pathogenic. The variant received 10 ACMG points.

• PVS1: Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant located near the start codon (<100nt), not predicted to undergo nonsense mediated mRNA decay. There are 106 pathogenic variants in the truncated region.
• PM2: Very rare variant in population databases, with high coverage

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.19_20insGGGTG	p.Lys7ArgfsTer5	frameshift splice_region	Exon 1 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.19_20insGGGTG	p.Lys7ArgfsTer5	frameshift splice_region	Exon 1 of 29	ENSP00000243344.7	Q7Z4L5-1
	TTC21B	ENST00000464374.5	TSL:1	n.59_60insGGGTG		splice_region non_coding_transcript_exon	Exon 1 of 11
	TTC21B	ENST00000679840.1		c.19_20insGGGTG	p.Lys7ArgfsTer5	frameshift splice_region	Exon 1 of 27	ENSP00000505248.1	A0A7P0T8P4

Frequencies

GnomAD3 genomes Cov.: 26

GnomAD2 exomes AF: 0.00 AC: 0 AN: 54534 AF XY: 0.00

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000898 AC: 5 AN: 557028 Hom.: 0 Cov.: 36 AF XY: 0.0000107 AC XY: 3 AN XY: 279136

African (AFR) AF: 0.00 AC: 0 AN: 12208

American (AMR) AF: 0.00 AC: 0 AN: 11324

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 10652

East Asian (EAS) AF: 0.00 AC: 0 AN: 21502

South Asian (SAS) AF: 0.00 AC: 0 AN: 39616

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 25112

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 2740

European-Non Finnish (NFE) AF: 0.0000122 AC: 5 AN: 408310

Other (OTH) AF: 0.00 AC: 0 AN: 25564

GnomAD4 genome Cov.: 26

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
PhyloP100		0.36

Splicing

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Other links and lift over

dbSNP: rs759648976; hg19: chr2-166810196;