chr15-55319338-G-A

Variant names:

• chr15-55319338-G-A
• rs2055107012
• NM_004855.5:c.88G>A

Variant summary

Our verdict is Likely benign. Variant got -2 ACMG points: 2P and 4B. PM2 BP4_Strong

The NM_004855.5(PIGB):​c.88G>A​(p.Gly30Ser) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000014 in 1,429,376 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 15/20 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: PIGB NM_004855.5 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 0.288

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]

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]

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]

ACMG classification

Verdict is Likely_benign. Variant got -2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.049430758).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
PIGB	NM_004855.5	c.88G>A	p.Gly30Ser	missense_variant	Exon 1 of 12	ENST00000164305.10	NP_004846.4
PIGBOS1	NM_001308421.2	c.-550C>T		upstream_gene_variant		ENST00000436697.3	NP_001295350.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
PIGB	ENST00000164305.10	c.88G>A	p.Gly30Ser	missense_variant	Exon 1 of 12	1	NM_004855.5	ENSP00000164305.5
PIGB	ENST00000566999.5	c.88G>A	p.Gly30Ser	missense_variant	Exon 1 of 6	3		ENSP00000456531.1
PIGBOS1	ENST00000436697.3	c.-550C>T		upstream_gene_variant		2	NM_001308421.2	ENSP00000484893.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000140 AC: 2 AN: 1429376 Hom.: 0 Cov.: 31 AF XY: 0.00000141 AC XY: 1 AN XY: 707778

Gnomad4 AFR exome AF: 0.0000303

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

not provided Uncertain:1

Feb 20, 2022

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be tolerated. This sequence change replaces glycine, which is neutral and non-polar, with serine, which is neutral and polar, at codon 30 of the PIGB protein (p.Gly30Ser). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with PIGB-related conditions. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.10
BayesDel_addAF	Benign	-0.20	T
BayesDel_noAF	Benign	-0.53
CADD	Benign	9.9
DANN	Benign	0.94
DEOGEN2	Benign	0.00064	T;T;T
Eigen	Benign	-1.1
Eigen_PC	Benign	-1.1
FATHMM_MKL	Benign	0.051	N
LIST_S2	Benign	0.72	T;T;T
M_CAP	Benign	0.0063	T
MetaRNN	Benign	0.049	T;T;T
MetaSVM	Benign	-1.0	T
MutationAssessor	Benign	0.69	N;.;.
PrimateAI	Benign	0.30	T
PROVEAN	Benign	0.020	N;N;.
REVEL	Benign	0.039
Sift	Benign	0.61	T;T;.
Sift4G	Benign	0.28	T;T;T
Polyphen		0.15	B;.;.
Vest4		0.086
MutPred		0.17		Loss of sheet (P = 0.0181);Loss of sheet (P = 0.0181);Loss of sheet (P = 0.0181);
MVP		0.29
MPC		0.045
ClinPred		0.070	T
GERP RS		2.7
Varity_R		0.035
gMVP		0.28

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: rs2055107012; hg19: chr15-55611536;