chr12-123671310-T-TGGGG

Variant names:

• chr12-123671310-T-TGGGG
• rs863225222
• NM_024809.5:c.73_76dupGGGG

Variant summary

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

The NM_024809.5(TCTN2):​c.73_76dupGGGG​(p.Asp26GlyfsTer53) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,594 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: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: TCTN2 NM_024809.5 frameshift
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 0.591
• Publications: 0 publications found

Genes affected

TCTN2 (HGNC:25774): (tectonic family member 2) This gene encodes a type I membrane protein that belongs to the tectonic family. Studies in mice suggest that this protein may be involved in hedgehog signaling, and essential for ciliogenesis. Mutations in this gene are associated with Meckel syndrome type 8. Alternatively spliced transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Oct 2011]

TCTN2 Gene-Disease associations (from GenCC):

• Joubert syndrome 24

  Inheritance: AR Classification: DEFINITIVE, STRONG, MODERATE Submitted by: ClinGen, Labcorp Genetics (formerly Invitae), PanelApp Australia, G2P, Ambry Genetics
• Meckel syndrome, type 8

  Inheritance: AR Classification: STRONG Submitted by: PanelApp Australia
• Joubert syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• Meckel syndrome

  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 54 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_024809.5. 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
	TCTN2	NM_024809.5	MANE Select	c.73_76dupGGGG	p.Asp26GlyfsTer53	frameshift	Exon 1 of 18	NP_079085.2
	TCTN2	NM_001143850.3		c.73_76dupGGGG	p.Asp26GlyfsTer53	frameshift	Exon 1 of 18	NP_001137322.1	Q96GX1-2
	TCTN2	NM_001410989.1		c.73_76dupGGGG	p.Asp26GlyfsTer53	frameshift	Exon 1 of 17	NP_001397918.1	A0A7P0T8X4

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TCTN2	ENST00000303372.7	TSL:1 MANE Select	c.73_76dupGGGG	p.Asp26GlyfsTer53	frameshift	Exon 1 of 18	ENSP00000304941.5	Q96GX1-1
	TCTN2	ENST00000426174.6	TSL:2	c.73_76dupGGGG	p.Asp26GlyfsTer53	frameshift	Exon 1 of 18	ENSP00000395171.2	Q96GX1-2
	TCTN2	ENST00000965363.1		c.73_76dupGGGG	p.Asp26GlyfsTer53	frameshift	Exon 1 of 17	ENSP00000635422.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461594 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 727092

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.00 AC: 0 AN: 33480

American (AMR) AF: 0.00 AC: 0 AN: 44702

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26128

East Asian (EAS) AF: 0.00 AC: 0 AN: 39700

South Asian (SAS) AF: 0.00 AC: 0 AN: 86246

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53226

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5766

European-Non Finnish (NFE) AF: 8.99e-7 AC: 1 AN: 1111958

Other (OTH) AF: 0.00 AC: 0 AN: 60388

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 32

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
PhyloP100		0.59

Splicing

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

Other links and lift over

dbSNP: rs863225222; hg19: chr12-124155857;