Genetic Variant TUBB2B:p.Ser188Ser (chr6-3225525-C-G) – ACMG Classification: Likely_benign (-3 pts)

Variant summary

Our verdict is Likely benign. The variant received -3 ACMG points: 2P and 5B. PM2BP4_StrongBP7

The NM_178012.5(TUBB2B):c.564G>C(p.Ser188Ser) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Synonymous variant affecting the same amino acid position (i.e. S188S) has been classified as Likely benign.

Frequency

Genomes: not found (cov: 31)

Exomes 𝑓: 6.9e-7 ( 0 hom. )

Failed GnomAD Quality Control

Consequence

TUBB2B
NM_178012.5 synonymous

Scores

Clinical Significance

Not reported in ClinVar

Conservation

PhyloP100: -5.28

Publications

7 publications found

Variant links:

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

TUBB2B links:

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ACMG classification

Classification was made for transcript

Our verdict: Likely_benign. The variant received -3 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

BP4

Computational evidence support a benign effect (BayesDel_noAF=-0.9).

BP7

Synonymous conserved (PhyloP=-5.28 with no splicing effect.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TUBB2B	NM_178012.5 link	c.564G>C	p.Ser188Ser	synonymous_variant	Exon 4 of 4	ENST00000259818.8	NP_821080.1	Q9BVA1A0A384MEE3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TUBB2B	ENST00000259818.8 link	c.564G>C	p.Ser188Ser	synonymous_variant	Exon 4 of 4	1	NM_178012.5	ENSP00000259818.6		Q9BVA1

Frequencies

GnomAD3 genomes

Cov.:

GnomAD4 exome

Data not reliable, filtered out with message: AS_VQSR

AF:

6.88e-7

AC:

AN:

1453078

Hom.:

Cov.:

AF XY:

0.00000138

AC XY:

AN XY:

722794

show subpopulations

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR)

AF:

0.00

AC:

AN:

30508

American (AMR)

AF:

0.00

AC:

AN:

44304

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26108

East Asian (EAS)

AF:

0.00

AC:

AN:

38550

South Asian (SAS)

AF:

0.00

AC:

AN:

84458

European-Finnish (FIN)

AF:

0.00

AC:

AN:

52916

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5686

European-Non Finnish (NFE)

AF:

9.00e-7

AC:

AN:

1110952

Other (OTH)

AF:

0.00

AC:

AN:

59596

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.225

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

GnomAD4 genome

Cov.:

Alfa

AF:

0.00

Hom.:

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_noAF

Benign

-0.90

CADD

Benign

0.13

(source)

DANN

Benign

0.44

PhyloP100

-5.3

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.020

Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

ClinVar

Computational scores

Splicing

Publications

Other links and lift over