Genetic Variant C8B:p.Arg428Gly (chr1-56940965-G-C) – ACMG Classification: Uncertain_significance (4 pts)

Variant summary

Our verdict is Uncertain significance. The variant received 4 ACMG points: 4P and 0B. PM2PP3_Moderate

The NM_000066.4(C8B):c.1282C>G(p.Arg428Gly) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000031 in 1,613,642 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R428Q) has been classified as Uncertain significance.

Frequency

Genomes: 𝑓 0.000020 ( 0 hom., cov: 32)

Exomes 𝑓: 0.0000014 ( 0 hom. )

Consequence

C8B
NM_000066.4 missense

Scores

Clinical Significance

Not reported in ClinVar

Conservation

PhyloP100: 3.04

Publications

26 publications found

Variant links:

Genes affected

C8B (HGNC:1353): (complement C8 beta chain) This gene encodes one of the three subunits of the complement component 8 (C8) protein. C8 is composed of equimolar amounts of alpha, beta and gamma subunits, which are encoded by three separate genes. C8 is one component of the membrane attack complex, which mediates cell lysis, and it initiates membrane penetration of the complex. This protein mediates the interaction of C8 with the C5b-7 membrane attack complex precursor. In humans deficiency of this protein is associated with increased risk of meningococcal infections. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Jun 2013]

C8B Gene-Disease associations (from GenCC):

type II complement component 8 deficiency
Inheritance: AR Classification: STRONG, MODERATE Submitted by: Ambry Genetics, Labcorp Genetics (formerly Invitae)

C8B links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Uncertain_significance. The variant received 4 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

PP3

MetaRNN computational evidence supports a deleterious effect, 0.919

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein
C8B	NM_000066.4 link	c.1282C>G	p.Arg428Gly	missense_variant	Exon 9 of 12	ENST00000371237.9	NP_000057.3
C8B	NM_001278543.2 link	c.1126C>G	p.Arg376Gly	missense_variant	Exon 10 of 13		NP_001265472.2
C8B	NM_001278544.2 link	c.1096C>G	p.Arg366Gly	missense_variant	Exon 10 of 13		NP_001265473.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
C8B	ENST00000371237.9 link	c.1282C>G	p.Arg428Gly	missense_variant	Exon 9 of 12	1	NM_000066.4	ENSP00000360281.4

Frequencies

GnomAD3 genomes

AF:

0.0000198

AC:

AN:

151788

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000727

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.00

Gnomad OTH

AF:

0.00

GnomAD2 exomes

AF:

0.00000398

AC:

AN:

251214

AF XY:

0.00000737

show subpopulations

Gnomad AFR exome

AF:

0.0000615

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000137

AC:

AN:

1461854

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

727230

show subpopulations

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

African (AFR)

AF:

0.0000299

AC:

AN:

33476

American (AMR)

AF:

0.00

AC:

AN:

44722

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26136

East Asian (EAS)

AF:

0.00

AC:

AN:

39696

South Asian (SAS)

AF:

0.00

AC:

AN:

86258

European-Finnish (FIN)

AF:

0.00

AC:

AN:

53416

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5768

European-Non Finnish (NFE)

AF:

0.00

AC:

AN:

1111992

Other (OTH)

AF:

0.0000166

AC:

AN:

60390

⚠️ 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: 0.375

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

AF:

0.0000198

AC:

AN:

151788

Hom.:

Cov.:

AF XY:

0.0000135

AC XY:

AN XY:

74110

show subpopulations

African (AFR)

AF:

0.0000727

AC:

AN:

41286

American (AMR)

AF:

0.00

AC:

AN:

15238

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3462

East Asian (EAS)

AF:

0.00

AC:

AN:

5134

South Asian (SAS)

AF:

0.00

AC:

AN:

4798

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10596

Middle Eastern (MID)

AF:

0.00

AC:

AN:

316

European-Non Finnish (NFE)

AF:

0.00

AC:

AN:

67962

Other (OTH)

AF:

0.00

AC:

AN:

2084

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.575

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Genome 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

Alfa

AF:

0.00

Hom.:

Bravo

AF:

0.00000378

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.21

BayesDel_addAF

Uncertain

0.11

BayesDel_noAF

Uncertain

0.10

CADD

Uncertain

(source)

DANN

Uncertain

1.0

DEOGEN2

Benign

0.0

.;T;.

Eigen

Uncertain

0.46

Eigen_PC

Uncertain

0.35

FATHMM_MKL

Uncertain

0.95

LIST_S2

Benign

0.0

.;D;D

M_CAP

Uncertain

0.16

MetaRNN

Pathogenic

0.92

D;D;D

MetaSVM

Uncertain

0.50

MutationAssessor

Benign

0.0

.;.;.

PhyloP100

3.0

PrimateAI

Benign

0.43

PROVEAN

Pathogenic

-5.0

D;D;D

REVEL

Pathogenic

0.68

Sift

Uncertain

0.0020

D;D;D

Sift4G

Uncertain

0.0040

D;D;D

Vest4

0.70

ClinPred

0.99

GERP RS

3.5

gMVP

0.92

Mutation Taster

=37/63

disease causing

(source)

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

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

Age Distribution

ClinVar

Computational scores

Splicing

Publications

Other links and lift over