rs1555162242

Variant names:

• chr12-49185062-A-G
• rs1555162242
• NM_006009.4:c.1304T>C

Variant summary

Our verdict is Likely pathogenic. The variant received 8 ACMG points: 8P and 0B. PM1 PM2 PM5 PP2 PP5

The NM_006009.4(TUBA1A):​c.1304T>C​(p.Val435Ala) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. V435L) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 31)
• Consequence: TUBA1A NM_006009.4 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2 U:1
• Conservation: PhyloP100: 8.87
• Publications: 0 publications found

Genes affected

TUBA1A (HGNC:20766): (tubulin alpha 1a) Microtubules of the eukaryotic cytoskeleton perform essential and diverse functions and are composed of a heterodimer of alpha and beta tubulins. The genes encoding these microtubule constituents belong to the tubulin superfamily, which is composed of six distinct families. Genes from the alpha, beta and gamma tubulin families are found in all eukaryotes. The alpha and beta tubulins represent the major components of microtubules, while gamma tubulin plays a critical role in the nucleation of microtubule assembly. There are multiple alpha and beta tubulin genes, which are highly conserved among species. This gene encodes alpha tubulin and is highly similar to the mouse and rat Tuba1 genes. Northern blot studies have shown that the gene expression is predominantly found in morphologically differentiated neurologic cells. This gene is one of three alpha-tubulin genes in a cluster on chromosome 12q. Mutations in this gene cause lissencephaly type 3 (LIS3) - a neurological condition characterized by microcephaly, intellectual disability, and early-onset epilepsy caused by defective neuronal migration. Alternative splicing results in multiple transcript variants encoding distinct isoforms. [provided by RefSeq, Jul 2017]

TUBA1B-AS1 (HGNC:56356): (TUBA1B antisense RNA 1)

ACMG classification

Our verdict: Likely_pathogenic. The variant received 8 ACMG points.

• PM1: In a hotspot region, there are 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 2 uncertain in NM_006009.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr12-49185063-C-G is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 3911723.Status of the report is criteria_provided_single_submitter, 1 stars.
• PP2: Missense variant in the TUBA1A gene, where missense mutations are typically associated with disease (based on misZ statistic). The gene has 163 curated pathogenic missense variants (we use a threshold of 10). The gene has 25 curated benign missense variants. Gene score misZ: 5.584 (above the threshold of 3.09). Trascript score misZ: 8.7455 (above the threshold of 3.09). GenCC associations: The gene is linked to tubulinopathy, lissencephaly due to TUBA1A mutation, tubulinopathy-associated dysgyria.
• PP5: Variant 12-49185062-A-G is Pathogenic according to our data. Variant chr12-49185062-A-G is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 437120.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TUBA1A	NM_006009.4	c.1304T>C	p.Val435Ala	missense_variant	Exon 4 of 4	ENST00000301071.12	NP_006000.2
TUBA1A	NM_001270399.2	c.1304T>C	p.Val435Ala	missense_variant	Exon 4 of 4		NP_001257328.1
TUBA1A	NM_001270400.2	c.1199T>C	p.Val400Ala	missense_variant	Exon 4 of 4		NP_001257329.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TUBA1A	ENST00000301071.12	c.1304T>C	p.Val435Ala	missense_variant	Exon 4 of 4	1	NM_006009.4	ENSP00000301071.7

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 31

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Lissencephaly due to TUBA1A mutation Pathogenic:1

Sep 06, 2016

Genetic Services Laboratory, University of Chicago

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Tubulinopathy Pathogenic:1

Jul 01, 2018

Institute of Human Genetics, FAU Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: literature only

A variant that is classified as likely pathogenic has been identified in the TUBA1A gene in a born individual of unknown sex. The c.1304T>C, p.(Val435Ala) variant has been reported as a variant of germline/unknown origin. -

not provided Uncertain:1

Nov 30, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces valine, which is neutral and non-polar, with alanine, which is neutral and non-polar, at codon 435 of the TUBA1A protein (p.Val435Ala). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with TUBA1A-related conditions (PMID: 30744660). ClinVar contains an entry for this variant (Variation ID: 437120). Invitae Evidence Modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) indicates that this missense variant is not expected to disrupt TUBA1A protein function with a negative 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	0.97
BayesDel_addAF	Pathogenic	0.29	D
BayesDel_noAF	Pathogenic	0.18
CADD	Uncertain	24
DANN	Benign	0.96
DEOGEN2	Uncertain	0.51	D;D;.
Eigen	Uncertain	0.29
Eigen_PC	Uncertain	0.44
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.91	.;D;D
M_CAP	Pathogenic	0.53	D
MetaRNN	Uncertain	0.73	D;D;D
MetaSVM	Uncertain	-0.061	T
MutationAssessor	Benign	2.0	M;M;.
PhyloP100		8.9
PrimateAI	Uncertain	0.72	T
PROVEAN	Uncertain	-2.4	N;N;N
REVEL	Pathogenic	0.67
Sift	Pathogenic	0.0	D;D;.
Sift4G	Benign	0.13	T;T;T
Polyphen		0.18	B;B;.
Vest4		0.66
MutPred		0.33		Gain of helix (P = 0.0093);Gain of helix (P = 0.0093);.;
MVP		0.91
MPC		2.2
ClinPred		0.96	D
GERP RS		5.5
RBP_binding_hub_radar		0.92
RBP_regulation_power_radar		2.6
Varity_R		0.88
gMVP		0.97
Mutation Taster		=5/95	disease causing (ClinVar)

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

Other links and lift over

dbSNP: rs1555162242; hg19: chr12-49578845;