22-19723572-G-C

Variant summary

Our verdict is Pathogenic. Variant got 13 ACMG points: 13P and 0B. PVS1 PS1_Moderate PM2 PP5

The NM_000407.5(GP1BB):c.3G>C(p.Met1?) variant causes a start lost change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (no stars).

• Frequency: Genomes: not found (cov: 33)
• Consequence: GP1BB NM_000407.5 start_lost
• Clinical Significance: Likely pathogenic no assertion criteria provided P:1
• Conservation: PhyloP100: 1.15

Genes affected

GP1BB (HGNC:4440): (glycoprotein Ib platelet subunit beta) Platelet glycoprotein Ib (GPIb) is a heterodimeric transmembrane protein consisting of a disulfide-linked 140 kD alpha chain and 22 kD beta chain. It is part of the GPIb-V-IX system that constitutes the receptor for von Willebrand factor (VWF), and mediates platelet adhesion in the arterial circulation. GPIb alpha chain provides the VWF binding site, and GPIb beta contributes to surface expression of the receptor and participates in transmembrane signaling through phosphorylation of its intracellular domain. Mutations in the GPIb beta subunit have been associated with Bernard-Soulier syndrome, velocardiofacial syndrome and giant platelet disorder. The 206 amino acid precursor of GPIb beta is synthesized from a 1.0 kb mRNA expressed in plateletes and megakaryocytes. A 411 amino acid protein arising from a longer, unspliced transcript in endothelial cells has been described; however, the authenticity of this product has been questioned. Yet another less abundant GPIb beta mRNA species of 3.5 kb, expressed in nonhematopoietic tissues such as endothelium, brain and heart, was shown to result from inefficient usage of a non-consensus polyA signal in the neighboring upstream gene (SEPT5, septin 5). In the absence of polyadenylation from its own imperfect site, the SEPT5 gene produces read-through transcripts that use the consensus polyA signal of this gene. [provided by RefSeq, Dec 2010]

SEPT5-GP1BB (HGNC:):

SEPTIN5 (HGNC:9164): (septin 5) This gene is a member of the septin gene family of nucleotide binding proteins, originally described in yeast as cell division cycle regulatory proteins. Septins are highly conserved in yeast, Drosophila, and mouse and appear to regulate cytoskeletal organization. Disruption of septin function disturbs cytokinesis and results in large multinucleate or polyploid cells. This gene is mapped to 22q11, the region frequently deleted in DiGeorge and velocardiofacial syndromes. A translocation involving the MLL gene and this gene has also been reported in patients with acute myeloid leukemia. Alternative splicing results in multiple transcript variants. The presence of a non-consensus polyA signal (AACAAT) in this gene also results in read-through transcription into the downstream neighboring gene (GP1BB; platelet glycoprotein Ib), whereby larger, non-coding transcripts are produced. [provided by RefSeq, Dec 2010]

ACMG classification

Verdict is Pathogenic. Variant got 13 ACMG points.

• PVS1: Start lost variant, no new inframe start found.
• PS1: Another start lost variant in NM_000407.5 (GP1BB) was described as [Pathogenic] in ClinVar as 1691253
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 22-19723572-G-C is Pathogenic according to our data. Variant chr22-19723572-G-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 812741.Status of the report is no_assertion_criteria_provided, 0 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GP1BB	NM_000407.5	c.3G>C	p.Met1?	start_lost	1/2	ENST00000366425.4
SEPT5-GP1BB	NR_037611.1	n.3743G>C		non_coding_transcript_exon_variant	11/12
SEPT5-GP1BB	NR_037612.1	n.2247G>C		non_coding_transcript_exon_variant	11/12

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GP1BB	ENST00000366425.4	c.3G>C	p.Met1?	start_lost	1/2	1	NM_000407.5	P1
SEPTIN5	ENST00000470814.1	n.1975G>C		non_coding_transcript_exon_variant	5/6	5

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 33

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1

Revision: no assertion criteria provided

Submissions by phenotype

Macrothrombocytopenia Pathogenic:1

Likely pathogenic, no assertion criteria provided

research

NIHR Bioresource Rare Diseases, University of Cambridge

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Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.56	D
BayesDel_noAF	Pathogenic	0.19
Cadd	Uncertain	24
Dann	Uncertain	0.99
DEOGEN2	Benign	0.32	T
Eigen	Benign	0.17
Eigen_PC	Benign	0.15
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.90	D
M_CAP	Pathogenic	1.0	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Benign	-0.28	T
MutationTaster	Benign	1.0	D
PROVEAN	Benign	-0.90	N
REVEL	Uncertain	0.53
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0	D
Polyphen		0.63	P
Vest4		0.85
MutPred		0.99		Loss of glycosylation at P5 (P = 0.1516);
MVP		0.97
ClinPred		0.99	D
GERP RS		3.3
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.84
gMVP		0.50

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: rs1601247763; hg19: chr22-19711095;