19-6495327-C-T

Variant names:

• chr19-6495327-C-T
• rs886041021
• NM_006087.4:c.1172G>A

Variant summary

Our verdict is Pathogenic. The variant received 18 ACMG points: 18P and 0B. PM1 PM2 PM5 PP3_Strong PP5_Very_Strong

The NM_006087.4(TUBB4A):​c.1172G>A​(p.Arg391His) 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. R391L) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: TUBB4A NM_006087.4 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:5 O:2
• Conservation: PhyloP100: 7.77
• Publications: 11 publications found

Genes affected

TUBB4A (HGNC:20774): (tubulin beta 4A class IVa) This gene encodes a member of the beta tubulin family. Beta tubulins are one of two core protein families (alpha and beta tubulins) that heterodimerize and assemble to form microtubules. Mutations in this gene cause hypomyelinating leukodystrophy-6 and autosomal dominant torsion dystonia-4. Alternate splicing results in multiple transcript variants encoding different isoforms. A pseudogene of this gene is found on chromosome X. [provided by RefSeq, Jan 2014]

TUBB4A Gene-Disease associations (from GenCC):

• hypomyelinating leukodystrophy 6

  Inheritance: AD Classification: DEFINITIVE, STRONG, MODERATE, SUPPORTIVE Submitted by: Genomics England PanelApp, Labcorp Genetics (formerly Invitae), Orphanet, Illumina
• TUBB4A-related neurologic disorder

  Inheritance: AD Classification: DEFINITIVE, MODERATE Submitted by: Ambry Genetics, ClinGen
• torsion dystonia 4

  Inheritance: AD Classification: STRONG, SUPPORTIVE Submitted by: Genomics England PanelApp, Labcorp Genetics (formerly Invitae), Orphanet

ACMG classification

Our verdict: Pathogenic. The variant received 18 ACMG points.

• PM1: In a hotspot region, there are 7 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 4 uncertain in NM_006087.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr19-6495327-C-A is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 419697.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.975
• PP5: Variant 19-6495327-C-T is Pathogenic according to our data. Variant chr19-6495327-C-T is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 267793.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TUBB4A	NM_006087.4	c.1172G>A	p.Arg391His	missense_variant	Exon 4 of 4	ENST00000264071.7	NP_006078.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TUBB4A	ENST00000264071.7	c.1172G>A	p.Arg391His	missense_variant	Exon 4 of 4	1	NM_006087.4	ENSP00000264071.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:5 Other:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:3

Feb 01, 2025

CeGaT Center for Human Genetics Tuebingen

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

TUBB4A: PM2, PM5, PM6, PS4:Moderate, PP2, PP3 -

May 10, 2023

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Not observed at significant frequency in large population cohorts (gnomAD); 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: 27809427, 26934450, 27159321, 35661708, 32681585, 36463079, 34997144, 34788679, 33547136, 34514881, 25085639, 35599849) -

Oct 23, 2020

Institute of Medical Genetics and Applied Genomics, University Hospital Tübingen

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Hypomyelinating leukodystrophy 6 Pathogenic:2 Other:1

Dec 29, 2020

Molecular Diagnostics Lab, Nemours Children's Health, Delaware

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This missense variant (c.1172G>A, p.Arg391Met) has not been observed in population databases (gnomAD). It has been reported in the literature (PMID 25085639). Variant prediction programs suggest a deleterious effect, although no functional studies have been published. -

-

GeneReviews

Significance: not provided

Review Status: no classification provided

Collection Method: literature only

- -

Jul 16, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

For these reasons, this variant has been classified as Pathogenic. This sequence change replaces arginine, which is basic and polar, with histidine, which is basic and polar, at codon 391 of the TUBB4A protein (p.Arg391His). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with clinical features of hypomyelinating leukodystrophy (PMID: 25085639; Invitae). In at least one individual the variant was observed to be de novo. ClinVar contains an entry for this variant (Variation ID: 267793). 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 TUBB4A protein function. -

Torsion dystonia 4;C2676244:Hypomyelinating leukodystrophy 6 Other:1

-

GenomeConnect, ClinGen

Significance: not provided

Review Status: no classification provided

Collection Method: phenotyping only

Variant interpretted as Pathogenic and reported on 03-12-2018 by Lab or GTR ID 239772. GenomeConnect assertions are reported exactly as they appear on the patient-provided report from the testing laboratory. GenomeConnect staff make no attempt to reinterpret the clinical significance of the variant. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.97
BayesDel_addAF	Pathogenic	0.17	D
BayesDel_noAF	Uncertain	0.010
CADD	Pathogenic	31
DANN	Uncertain	1.0
DEOGEN2	Benign	0.25	T
Eigen	Pathogenic	0.70
Eigen_PC	Uncertain	0.57
FATHMM_MKL	Uncertain	0.94	D
LIST_S2	Uncertain	0.86	D
M_CAP	Pathogenic	0.90	D
MetaRNN	Pathogenic	0.97	D
MetaSVM	Uncertain	0.79	D
MutationAssessor	Pathogenic	3.8	H
PhyloP100		7.8
PrimateAI	Pathogenic	0.92	D
PROVEAN	Uncertain	-2.5	D
REVEL	Pathogenic	0.96
Sift4G	Uncertain	0.028	D
Polyphen		1.0	D
Vest4		0.92
MutPred		0.86		Loss of MoRF binding (P = 0.0209);
MVP		0.92
MPC		2.8
ClinPred		0.99	D
GERP RS		3.4
Varity_R		0.77
gMVP		0.95
Mutation Taster		=9/91	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: rs886041021; hg19: chr19-6495338; COSMIC: COSV51152978; COSMIC: COSV51152978;