6-3224901-G-C

Position:

• chr6-3224901-G-C

Variant summary

Our verdict is Likely pathogenic. Variant got 7 ACMG points: 7P and 0B. PM2 PM5 PP2 PP3_Moderate

The NM_178012.5(TUBB2B):​c.1188C>G​(p.His396Gln) variant causes a missense change. 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 Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. H396R) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 20)
• Consequence: TUBB2B NM_178012.5 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 5.55

Genes affected

TUBB2B (HGNC:30829): (tubulin beta 2B class IIb) The protein encoded by this gene is a beta isoform of tubulin, which binds GTP and is a major component of microtubules. This gene is highly similar to TUBB2A and TUBB2C. Defects in this gene are a cause of asymmetric polymicrogyria. [provided by RefSeq, Mar 2010]

ACMG classification

Verdict is Likely_pathogenic. Variant got 7 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr6-3224902-T-C is described in Lovd as [Pathogenic].
• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), TUBB2B. . Gene score misZ 5.1195 (greater than the threshold 3.09). Trascript score misZ 6.9522 (greater than threshold 3.09). GenCC has associacion of gene with tubulinopathy-associated dysgyria, congenital fibrosis of extraocular muscles, cerebellar ataxia, intellectual disability, and dysequilibrium, complex cortical dysplasia with other brain malformations 7, complex cortical dysplasia with other brain malformations.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.934

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TUBB2B	NM_178012.5	c.1188C>G	p.His396Gln	missense_variant	4/4	ENST00000259818.8	NP_821080.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TUBB2B	ENST00000259818.8	c.1188C>G	p.His396Gln	missense_variant	4/4	1	NM_178012.5	ENSP00000259818	P1

Frequencies

GnomAD3 genomes Cov.: 20

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 20

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

GeneDx

Jul 01, 2015

The H396Q variant has not been published as a pathogenic variant, nor has it been reported as a benign polymorphism to our knowledge. It was not observed in approximately 6,400 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project, indicating it is not a common benign variant in these populations. The H396Q variant is a semi-conservative amino acid substitution, which may impact secondary protein structure as these residues differ in some properties. This substitution occurs at a position that is conserved across species, and in silico analysis predicts this variant is probably damaging to the protein structure/function. However, missense variants in nearby residues have not been reported in the Human Gene Mutation Database in association with TUBB2B-related disorders (Stenson et al., 2014). Therefore, based on the currently available information, it is unclear whether this variant is a pathogenic or a rare benign variant. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.45	D
BayesDel_noAF	Pathogenic	0.41
CADD	Uncertain	24
DANN	Uncertain	0.99
DEOGEN2	Uncertain	0.56	D
Eigen	Uncertain	0.67
Eigen_PC	Uncertain	0.65
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.96	D
M_CAP	Pathogenic	0.68	D
MetaRNN	Pathogenic	0.93	D
MetaSVM	Uncertain	0.74	D
MutationAssessor	Pathogenic	4.2	H
MutationTaster	Benign	1.0	D
PrimateAI	Pathogenic	0.93	D
PROVEAN	Uncertain	-4.1	D
REVEL	Pathogenic	0.88
Sift4G	Uncertain	0.013	D
Polyphen		0.88	P
Vest4		0.87
MutPred		0.75		Gain of MoRF binding (P = 0.0882);
MVP		0.79
ClinPred		1.0	D
GERP RS		5.1
Varity_R		0.91
gMVP		0.99

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: rs1554126865; hg19: chr6-3225135;