chr6-3225739-A-G

Variant names:

• chr6-3225739-A-G
• rs397514569
• NM_178012.5:c.350T>C

Variant summary

Our verdict is Likely pathogenic. The variant received 9 ACMG points: 9P and 0B. PM2 PP2 PP3_Strong PP5_Moderate

The NM_178012.5(TUBB2B):​c.350T>C​(p.Leu117Pro) 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. 13/22 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★).

• Frequency: Genomes: not found (cov: 31)
• Consequence: TUBB2B NM_178012.5 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:2
• Conservation: PhyloP100: 9.17
• Publications: 4 publications found

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]

TUBB2B Gene-Disease associations (from GenCC):

• complex cortical dysplasia with other brain malformations

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• complex cortical dysplasia with other brain malformations 7

  Inheritance: AD Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Labcorp Genetics (formerly Invitae), G2P, Orphanet
• congenital fibrosis of extraocular muscles

  Inheritance: AD Classification: SUPPORTIVE, LIMITED Submitted by: Orphanet, Genomics England PanelApp
• tubulinopathy-associated dysgyria

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• cerebellar ataxia, intellectual disability, and dysequilibrium

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Likely_pathogenic. The variant received 9 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant in the TUBB2B gene, where missense mutations are typically associated with disease (based on misZ statistic). The gene has 45 curated pathogenic missense variants (we use a threshold of 10). The gene has 2 curated benign missense variants. Gene score misZ: 5.1195 (above the threshold of 3.09). Trascript score misZ: 6.9522 (above the threshold of 3.09). GenCC associations: The gene is linked to tubulinopathy-associated dysgyria, congenital fibrosis of extraocular muscles, complex cortical dysplasia with other brain malformations 7, complex cortical dysplasia with other brain malformations, cerebellar ataxia, intellectual disability, and dysequilibrium.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.982
• PP5: Variant 6-3225739-A-G is Pathogenic according to our data. Variant chr6-3225739-A-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 39722.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TUBB2B	NM_178012.5	c.350T>C	p.Leu117Pro	missense_variant	Exon 4 of 4	ENST00000259818.8	NP_821080.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TUBB2B	ENST00000259818.8	c.350T>C	p.Leu117Pro	missense_variant	Exon 4 of 4	1	NM_178012.5	ENSP00000259818.6

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 34

GnomAD4 genome Cov.: 31

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, single submitter

Submissions by phenotype

Complex cortical dysplasia with other brain malformations 7 Pathogenic:1

Sep 01, 2012

OMIM

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: literature only

- -

not provided Pathogenic:1

Nov 11, 2016

GeneDx

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The L117P variant in the TUBB2B gene has previously been reported in at least one patient with polymicrogyria (Guerrini et al., 2012). This variant 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 L117P 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. The L117P variant is a strong candidate for a pathogenic variant. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.40	D
BayesDel_noAF	Pathogenic	0.34
CADD	Pathogenic	27
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.57	D
Eigen	Pathogenic	1.0
Eigen_PC	Pathogenic	0.91
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.91	D
M_CAP	Pathogenic	0.51	D
MetaRNN	Pathogenic	0.98	D
MetaSVM	Uncertain	0.72	D
MutationAssessor	Pathogenic	4.9	H
PhyloP100		9.2
PrimateAI	Pathogenic	0.91	D
PROVEAN	Pathogenic	-4.5	D
REVEL	Pathogenic	0.94
Sift4G	Pathogenic	0.0010	D
Polyphen		1.0	D
Vest4		0.96
MutPred		0.86		Gain of disorder (P = 0.0216);
MVP		0.96
ClinPred		1.0	D
GERP RS		5.2
Varity_R		1.0
gMVP		1.0
Mutation Taster		=0/100	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: rs397514569; hg19: chr6-3225973;