rs747480526

chr16-89934984-C-T

Variant summary

Our verdict is Pathogenic. Variant got 15 ACMG points: 15P and 0B. PM1 PM2 PP2 PP3_Moderate PP5_Very_Strong

The NM_006086.4(TUBB3):c.533C>T(p.Thr178Met) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★). Synonymous variant affecting the same amino acid position (i.e. T178T) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 33)
• Consequence: TUBB3 NM_006086.4 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:5
• Conservation: PhyloP100: 7.78

Genes affected

TUBB3 (HGNC:20772): (tubulin beta 3 class III) This gene encodes a class III member of the beta tubulin protein family. Beta tubulins are one of two core protein families (alpha and beta tubulins) that heterodimerize and assemble to form microtubules. This protein is primarily expressed in neurons and may be involved in neurogenesis and axon guidance and maintenance. Mutations in this gene are the cause of congenital fibrosis of the extraocular muscles type 3. Alternate splicing results in multiple transcript variants. A pseudogene of this gene is found on chromosome 6. [provided by RefSeq, Oct 2010]

ACMG classification

Verdict is Pathogenic. Variant got 15 ACMG points.

• PM1: In a hotspot region, there are 2 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 5 uncertain in NM_006086.4
• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant where missense usually causes diseases, TUBB3
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.904
• PP5: Variant 16-89934984-C-T is Pathogenic according to our data. Variant chr16-89934984-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 265335.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TUBB3	NM_006086.4	c.533C>T	p.Thr178Met	missense_variant	4/4	ENST00000315491.12
TUBB3	NM_001197181.2	c.317C>T	p.Thr106Met	missense_variant	4/4

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TUBB3	ENST00000315491.12	c.533C>T	p.Thr178Met	missense_variant	4/4	1	NM_006086.4	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251474 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135916

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 SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000879

Gnomad OTH exome AF: 0.00

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 33

ExAC AF: 0.00000824 AC: 1

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:5

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Aug 01, 2022	Published functional studies suggest that T178M impacts the function of the protein (Poirier et al., 2010, Park et al., 2021); Not observed at a significant frequency in large population cohorts (gnomAD); Missense variants in this gene are often considered pathogenic (HGMD); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; This variant is associated with the following publications: (PMID: 26639658, 24860126, 21292473, 22669706, 26934450, 28726809, 29261186, 29382549, 31226147, 32169460, 20829227, 34869359) -
Pathogenic, criteria provided, single submitter	clinical testing	Invitae	Aug 11, 2023	For these reasons, this variant has been classified as Pathogenic. Experimental studies have shown that this missense change affects TUBB3 function (PMID: 20829227, 29382549). 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 expected to disrupt TUBB3 protein function. ClinVar contains an entry for this variant (Variation ID: 265335). This missense change has been observed in individual(s) with cortical dysplasia with other brain malformations (PMID: 20829227, 28726809, 29261186). In at least one individual the variant was observed to be de novo. The frequency data for this variant in the population databases is considered unreliable, as metrics indicate poor data quality at this position in the gnomAD database. This sequence change replaces threonine, which is neutral and polar, with methionine, which is neutral and non-polar, at codon 178 of the TUBB3 protein (p.Thr178Met). -

Complex cortical dysplasia with other brain malformations 1 Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	Victorian Clinical Genetics Services, Murdoch Childrens Research Institute	Jun 24, 2022	Based on the classification scheme VCGS_Germline_v1.3.4, this variant is classified as Pathogenic. Following criteria are met: 0104 - Dominant negative is a known mechanism of disease in this gene and is associated with cortical dysplasia, complex, with other brain malformations 1 (MIM#614039) (PMID: 31219644). (I) 0107 - This gene is associated with autosomal dominant disease. (I) 0200 - Variant is predicted to result in a missense amino acid change from threonine to methionine. (I) 0251 - This variant is heterozygous. (I) 0302 - Variant is present in gnomAD (v2) <0.001 for a dominant condition (1 heterozygote, 0 homozygotes). (SP) 0502 - Missense variant with conflicting in silico predictions and uninformative conservation. (I) 0603 - Missense variant in a region that is highly intolerant to missense variation (high constraint region in DECIPHER). (SP) 0705 - No comparable missene variants have previous evidence for pathogenicity. (I) 0801 - This variant has strong previous evidence of pathogenicity in unrelated individuals. This variant has been reported in one de novo individual with malformation of the cortical development and another heterozygous individual with fetal brain malformation (PMID: 20829227, 34869359). It has also been reported as pathogenic, likely pathogenic and VUS in ClinVar. (SP) 0905 - No published segregation evidence has been identified for this variant. (I) 1001 - This variant has strong functional evidence supporting abnormal protein function. Functional studies using patient fibroblasts showed this variant reduced microtubule stablity (PMID: 20829227). (SP) 1203 - This variant has been shown to be de novo in the proband (parental status confirmed) (by trio analysis). (SP) Legend: (SP) - Supporting pathogenic, (I) - Information, (SB) - Supporting benign -
Pathogenic, no assertion criteria provided	literature only	OMIM	Nov 15, 2010	- -

Inborn genetic diseases Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Nov 09, 2017

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.95
BayesDel_addAF	Pathogenic	0.40	D
BayesDel_noAF	Pathogenic	0.34
Cadd	Uncertain	24
Dann	Uncertain	1.0
Eigen	Pathogenic	0.89
Eigen_PC	Pathogenic	0.75
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.89	D;D;D;D
M_CAP	Pathogenic	0.47	D
MetaRNN	Pathogenic	0.90	D;D;D;D
MetaSVM	Uncertain	0.71	D
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Pathogenic	0.84	D
PROVEAN	Pathogenic	-5.0	D;D;D;D
REVEL	Pathogenic	0.79
Sift	Pathogenic	0.0	D;.;.;.
Sift4G	Uncertain	0.013	D;D;D;D
Polyphen		1.0	.;.;.;D
Vest4		0.89
MVP		0.96
MPC		2.8
ClinPred		1.0	D
GERP RS		4.7
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		2.7
Varity_R		0.96
gMVP		0.92

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

LitVar

Other links and lift over

dbSNP: rs747480526; hg19: chr16-90001392; COSMIC: COSV59247036; COSMIC: COSV59247036;