NM_004855.5:c.58A>G

Variant names:

Variant summary

Our verdict is Likely benign. The variant received -2 ACMG points: 2P and 4B. PM2BP4_Strong

The NM_004855.5(PIGB):c.58A>G(p.Thr20Ala) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000799 in 1,602,508 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 16/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

Frequency

Genomes: 𝑓 0.000066 ( 0 hom., cov: 32)

Exomes 𝑓: 0.000081 ( 0 hom. )

Consequence

PIGB
NM_004855.5 missense

Scores

Clinical Significance

Uncertain significance criteria provided, multiple submitters, no conflicts U:2

Conservation

PhyloP100: 1.46

Publications

0 publications found

Variant links:

Genes affected

PIGB (HGNC:8959): (phosphatidylinositol glycan anchor biosynthesis class B) This gene encodes a transmembrane protein that is located in the endoplasmic reticulum and is involved in GPI-anchor biosynthesis. The glycosylphosphatidylinositol (GPI) anchor is a glycolipid found on many blood cells and serves to anchor proteins to the cell surface. This gene is thought to encode a member of a family of dolichol-phosphate-mannose (Dol-P-Man) dependent mannosyltransferases. [provided by RefSeq, Jul 2008]

PIGB links:

PIGBOS1 (HGNC:50696): (PIGB opposite strand 1) Involved in regulation of endoplasmic reticulum unfolded protein response. Is integral component of mitochondrial outer membrane. [provided by Alliance of Genome Resources, Apr 2022]

PIGBOS1 links:

RAB27A (HGNC:9766): (RAB27A, member RAS oncogene family) The protein encoded by this gene belongs to the small GTPase superfamily, Rab family. The protein is membrane-bound and may be involved in protein transport and small GTPase mediated signal transduction. Mutations in this gene are associated with Griscelli syndrome type 2. Alternative splicing occurs at this locus and four transcript variants encoding the same protein have been identified. [provided by RefSeq, Jul 2008]

RAB27A Gene-Disease associations (from GenCC):

Griscelli syndrome type 2
Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: ClinGen, Labcorp Genetics (formerly Invitae), Orphanet

RAB27A links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Likely_benign. The variant received -2 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

BP4

Computational evidence support a benign effect (MetaRNN=0.038390696).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
PIGB	NM_004855.5 link	c.58A>G	p.Thr20Ala	missense_variant	Exon 1 of 12	ENST00000164305.10	NP_004846.4	Q92521
PIGBOS1	NM_001308421.2 link	c.-520T>C		upstream_gene_variant		ENST00000436697.3	NP_001295350.1	A0A0B4J2F0

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	UniProt
PIGB	ENST00000164305.10 link	c.58A>G	p.Thr20Ala	missense_variant	Exon 1 of 12	1	NM_004855.5	ENSP00000164305.5	Q92521
PIGB	ENST00000566999.5 link	c.58A>G	p.Thr20Ala	missense_variant	Exon 1 of 6	3		ENSP00000456531.1	H3BS45
PIGBOS1	ENST00000436697.3 link	c.-520T>C		upstream_gene_variant		2	NM_001308421.2	ENSP00000484893.1	A0A0B4J2F0

Frequencies

GnomAD3 genomes

AF:

0.0000657

AC:

AN:

152210

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000483

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:

0.000118

Gnomad OTH

AF:

0.00

GnomAD2 exomes

AF:

0.0000264

AC:

AN:

226882

AF XY:

0.0000163

show subpopulations

Gnomad AFR exome

AF:

0.00

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:

0.0000586

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.0000814

AC:

118

AN:

1450298

Hom.:

Cov.:

AF XY:

0.0000847

AC XY:

AN XY:

720078

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

33336

American (AMR)

AF:

0.0000233

AC:

AN:

42966

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

25684

East Asian (EAS)

AF:

0.00

AC:

AN:

39470

South Asian (SAS)

AF:

0.00

AC:

AN:

83544

European-Finnish (FIN)

AF:

0.00

AC:

AN:

52536

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5748

European-Non Finnish (NFE)

AF:

0.0000994

AC:

110

AN:

1107066

Other (OTH)

AF:

0.000117

AC:

AN:

59948

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.483

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

GnomAD4 genome

AF:

0.0000657

AC:

AN:

152210

Hom.:

Cov.:

AF XY:

0.0000269

AC XY:

AN XY:

74364

show subpopulations

African (AFR)

AF:

0.0000483

AC:

AN:

41450

American (AMR)

AF:

0.00

AC:

AN:

15278

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3472

East Asian (EAS)

AF:

0.00

AC:

AN:

5202

South Asian (SAS)

AF:

0.00

AC:

AN:

4828

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10626

Middle Eastern (MID)

AF:

0.00

AC:

AN:

316

European-Non Finnish (NFE)

AF:

0.000118

AC:

AN:

68036

Other (OTH)

AF:

0.00

AC:

AN:

2090

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.505

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Alfa

AF:

0.0000282

Hom.:

Bravo

AF:

0.0000680

TwinsUK

AF:

0.00

AC:

ALSPAC

AF:

0.000259

AC:

ExAC

AF:

0.0000249

AC:

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

Inborn genetic diseases

Uncertain:1

Apr 11, 2025

Ambry Genetics

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

The c.58A>G (p.T20A) alteration is located in exon 1 (coding exon 1) of the PIGB gene. This alteration results from a A to G substitution at nucleotide position 58, causing the threonine (T) at amino acid position 20 to be replaced by an alanine (A). Based on insufficient or conflicting evidence, the clinical significance of this alteration remains unclear. -

not provided

Uncertain:1

Jun 28, 2022

Labcorp Genetics (formerly Invitae), Labcorp

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

This sequence change replaces threonine, which is neutral and polar, with alanine, which is neutral and non-polar, at codon 20 of the PIGB protein (p.Thr20Ala). The frequency data for this variant in the population databases is considered unreliable, as metrics indicate poor data quality at this position in the gnomAD database. This variant has not been reported in the literature in individuals affected with PIGB-related conditions. Algorithms developed to predict the effect of missense changes on protein structure and function output the following: SIFT: "Tolerated"; PolyPhen-2: "Benign"; Align-GVGD: "Class C0". The alanine amino acid residue is found in multiple mammalian species, which suggests that this missense change does not adversely affect protein function. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.061

BayesDel_addAF

Benign

-0.21

BayesDel_noAF

Benign

-0.54

CADD

Benign

5.4

(source)

DANN

Benign

0.62

DEOGEN2

Benign

0.0012

T;T;T

Eigen

Benign

-1.4

Eigen_PC

Benign

-1.3

FATHMM_MKL

Benign

0.0096

LIST_S2

Benign

0.34

T;T;T

M_CAP

Benign

0.0030

MetaRNN

Benign

0.038

T;T;T

MetaSVM

Benign

-1.0

MutationAssessor

Benign

-0.050

N;.;.

PhyloP100

1.5

PrimateAI

Benign

0.38

PROVEAN

Benign

-0.090

N;N;.

REVEL

Benign

0.069

Sift

Benign

0.52

T;T;.

Sift4G

Benign

0.70

T;T;T

Polyphen

0.0

B;.;.

Vest4

0.026

MVP

0.28

MPC

0.042

ClinPred

0.044

GERP RS

1.6

PromoterAI

0.037

Neutral

(source)

Varity_R

0.042

gMVP

0.21

Mutation Taster

=98/2

polymorphism

(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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NM_004855.5:c.58A>G

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over