rs1555162407

Positions:

• chr12-49185942-C-A
• chr12-49185942-C-T

Variant summary

Our verdict is Pathogenic. Variant got 17 ACMG points: 17P and 0B. PM1 PM2 PM5 PP2 PP3_Moderate PP5_Very_Strong

The ENST00000301071.12(TUBA1A):​c.424G>T​(p.Gly142Cys) 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 (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. G142S) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: TUBA1A ENST00000301071.12 missense
• Clinical Significance: Likely pathogenic criteria provided, multiple submitters, no conflicts P:2
• Conservation: PhyloP100: 7.49

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

Verdict is Pathogenic. Variant got 17 ACMG points.

• PM1: In a hotspot region, there are 6 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 3 uncertain in ENST00000301071.12
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr12-49185942-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 520702.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), TUBA1A. . Gene score misZ 5.584 (greater than the threshold 3.09). Trascript score misZ 8.7455 (greater than threshold 3.09). GenCC has associacion of gene with tubulinopathy-associated dysgyria, intellectual disability, autosomal dominant 40, tubulinopathy, lissencephaly due to TUBA1A mutation.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.921
• PP5: Variant 12-49185942-C-A is Pathogenic according to our data. Variant chr12-49185942-C-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 431839.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr12-49185942-C-A is described in Lovd as [Likely_pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TUBA1A	NM_006009.4	c.424G>T	p.Gly142Cys	missense_variant	4/4	ENST00000301071.12	NP_006000.2
TUBA1A	NM_001270399.2	c.424G>T	p.Gly142Cys	missense_variant	4/4		NP_001257328.1
TUBA1A	NM_001270400.2	c.319G>T	p.Gly107Cys	missense_variant	4/4		NP_001257329.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TUBA1A	ENST00000301071.12	c.424G>T	p.Gly142Cys	missense_variant	4/4	1	NM_006009.4	ENSP00000301071	P1
TUBA1B-AS1	ENST00000656133.1	n.474-2341C>A		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 34

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Apr 10, 2017

A variant that is likely pathogenic has been identified in the TUBA1A gene. The G142C variant has not been published as a pathogenic variant, nor has it been reported as a benign variant to our knowledge. The G142C variant is not observed in large population cohorts (Lek et al., 2016; 1000 Genomes Consortium et al., 2015; Exome Variant Server). The G142C variant is a non-conservative amino acid substitution, which is likely to impact secondary protein structure as these residues differ in polarity, charge, size and/or other properties. This substitution alters a highly conserved position in the predicted GTP binding domain of the TUBA1A protein. A missense variant in a nearby residue (V137D) has been reported in association with lissencephaly with cerebellar hypoplasia; however, the clinical significance of the V137D change is unknown as parental studies were not performed (Kumar et al, 2010). In silico analysis predicts the G142C variant is probably damaging to the protein structure/function. Additionally, targeted parental testing indicates this variant is apparently de novo. Therefore, this variant is likely pathogenic; however, the possibility that it is benign cannot be excluded. -

Tubulinopathy Pathogenic:1

Likely pathogenic, criteria provided, single submitter

literature only

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

Jul 01, 2018

A variant that is classified as likely pathogenic has been identified in the TUBA1A gene in a born individual of unknown sex. The c.424G>T, p.(Gly142Cys) variant has been reported as a variant of germline/unknown origin. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.42	D
BayesDel_noAF	Pathogenic	0.36
CADD	Uncertain	25
DANN	Uncertain	0.98
DEOGEN2	Uncertain	0.72	D;D;.;T;.
Eigen	Pathogenic	0.72
Eigen_PC	Pathogenic	0.68
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	0.97	.;D;D;D;D
M_CAP	Pathogenic	0.89	D
MetaRNN	Pathogenic	0.92	D;D;D;D;D
MetaSVM	Uncertain	0.75	D
MutationAssessor	Pathogenic	4.6	H;H;.;.;.
MutationTaster	Benign	1.0	D;D;D;D;D;D;D
PrimateAI	Pathogenic	0.84	D
PROVEAN	Pathogenic	-6.3	D;D;D;D;D
REVEL	Pathogenic	0.90
Sift	Pathogenic	0.0	D;D;.;.;.
Sift4G	Uncertain	0.016	D;D;D;.;D
Polyphen		1.0	D;D;.;.;.
Vest4		0.85
MutPred		0.69		Gain of catalytic residue at S147 (P = 0);Gain of catalytic residue at S147 (P = 0);.;.;.;
MVP		0.87
MPC		3.5
ClinPred		1.0	D
GERP RS		4.8
Varity_R		0.99
gMVP		1.0

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: rs1555162407; hg19: chr12-49579725;