chr16-89923450-G-C

Position:

• chr16-89923450-G-C

Variant summary

Our verdict is Likely pathogenic. Variant got 7 ACMG points: 7P and 0B. PM2 PP2 PP3_Strong

The NM_006086.4(TUBB3):​c.49G>C​(p.Gly17Arg) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000738 in 1,354,292 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 12/21 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 7.4e-7 (0 hom.)
• Consequence: TUBB3 NM_006086.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 9.15

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 Likely_pathogenic. Variant got 7 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), TUBB3. . Gene score misZ 4.5786 (greater than the threshold 3.09). Trascript score misZ 5.665 (greater than threshold 3.09). GenCC has associacion of gene with tubulinopathy-associated dysgyria, complex cortical dysplasia with other brain malformations 1, congenital fibrosis of extraocular muscles, fibrosis of extraocular muscles, congenital, 3A, with or without extraocular involvement.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.986

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TUBB3	NM_006086.4	c.49G>C	p.Gly17Arg	missense_variant	1/4	ENST00000315491.12	NP_006077.2
TUBB3	NM_001197181.2	c.-160+1205G>C		intron_variant			NP_001184110.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TUBB3	ENST00000315491.12	c.49G>C	p.Gly17Arg	missense_variant	1/4	1	NM_006086.4	ENSP00000320295	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 7.38e-7 AC: 1 AN: 1354292 Hom.: 0 Cov.: 31 AF XY: 0.00000149 AC XY: 1 AN XY: 672572

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 9.44e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ExAC AF: 0.00000854 AC: 1

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Dec 21, 2023

This sequence change replaces glycine, which is neutral and non-polar, with arginine, which is basic and polar, at codon 17 of the TUBB3 protein (p.Gly17Arg). 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 variant has not been reported in the literature in individuals affected with TUBB3-related conditions. 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 with a positive predictive value of 80%. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.39	D
BayesDel_noAF	Pathogenic	0.32
CADD	Pathogenic	32
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.43	T;D;T;.;T
Eigen	Pathogenic	0.93
Eigen_PC	Pathogenic	0.73
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.90	D;D;D;D;D
M_CAP	Pathogenic	0.84	D
MetaRNN	Pathogenic	0.99	D;D;D;D;D
MetaSVM	Pathogenic	0.86	D
MutationAssessor	Pathogenic	4.8	.;H;.;.;.
MutationTaster	Benign	1.0	D;D;D;D;D
PrimateAI	Pathogenic	0.92	D
PROVEAN	Uncertain	-2.9	.;D;D;D;D
REVEL	Pathogenic	0.81
Sift	Pathogenic	0.0	.;.;D;D;D
Sift4G	Uncertain	0.0060	D;D;D;D;D
Polyphen		1.0	.;D;.;.;.
Vest4		0.92
MutPred		0.88		Gain of MoRF binding (P = 0.0646);Gain of MoRF binding (P = 0.0646);Gain of MoRF binding (P = 0.0646);Gain of MoRF binding (P = 0.0646);Gain of MoRF binding (P = 0.0646);
MVP		0.97
MPC		2.6
ClinPred		0.99	D
GERP RS		3.2
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.6
Varity_R		0.96
gMVP		1.0

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.030		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: rs778032071; hg19: chr16-89989858;