3-49722038-C-T

Variant names:

Variant summary

Our verdict is Uncertain significance. The variant received 2 ACMG points: 4P and 2B. PM1PM2BP4_Moderate

The NM_021971.4(GMPPB):c.878G>A(p.Arg293Gln) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000868 in 1,613,470 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 13/22 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R293W) has been classified as Uncertain significance.

Frequency

Genomes: 𝑓 0.000026 ( 0 hom., cov: 33)

Exomes 𝑓: 0.0000068 ( 0 hom. )

Consequence

GMPPB
NM_021971.4 missense

Scores

Clinical Significance

Uncertain significance criteria provided, single submitter U:1

Conservation

PhyloP100: 3.29

Publications

3 publications found

Variant links:

Genes affected

GMPPB (HGNC:22932): (GDP-mannose pyrophosphorylase B) This gene is thought to encode a GDP-mannose pyrophosphorylase. The encoded protein catalyzes the conversion of mannose-1-phosphate and GTP to GDP-mannose, a reaction involved in the production of N-linked oligosaccharides. Alternatively spliced transcript variants encoding distinct isoforms have been described. [provided by RefSeq, Jan 2009]

GMPPB Gene-Disease associations (from GenCC):

muscular dystrophy-dystroglycanopathy (congenital with brain and eye anomalies), type A14
Inheritance: AR Classification: DEFINITIVE, STRONG Submitted by: Ambry Genetics, Labcorp Genetics (formerly Invitae), G2P
myopathy caused by variation in GMPPB
Inheritance: AR Classification: DEFINITIVE Submitted by: ClinGen
autosomal recessive limb-girdle muscular dystrophy type 2T
Inheritance: AR Classification: STRONG, MODERATE, SUPPORTIVE Submitted by: Ambry Genetics, Labcorp Genetics (formerly Invitae), Orphanet, PanelApp Australia
congenital myasthenic syndrome
Inheritance: AR Classification: STRONG Submitted by: Genomics England PanelApp
congenital muscular dystrophy with cerebellar involvement
Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
congenital muscular dystrophy with intellectual disability
Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
congenital myasthenic syndromes with glycosylation defect
Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
muscle-eye-brain disease
Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

GMPPB links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Uncertain_significance. The variant received 2 ACMG points.

PM1

In a hotspot region, there are 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 6 uncertain in NM_021971.4

PM2

Very rare variant in population databases, with high coverage;

BP4

Computational evidence support a benign effect (MetaRNN=0.25667238).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
GMPPB	NM_021971.4 link	c.878G>A	p.Arg293Gln	missense_variant	Exon 8 of 9	ENST00000308388.7	NP_068806.2	Q9Y5P6-1
GMPPB	NM_013334.4 link	c.878G>A	p.Arg293Gln	missense_variant	Exon 8 of 8		NP_037466.3	Q9Y5P6-2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
GMPPB	ENST00000308388.7 link	c.878G>A	p.Arg293Gln	missense_variant	Exon 8 of 9	1	NM_021971.4	ENSP00000311130.6		Q9Y5P6-1

Frequencies

GnomAD3 genomes

AF:

0.0000263

AC:

AN:

152198

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000241

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.0000654

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:

0.0000294

Gnomad OTH

AF:

0.00

GnomAD2 exomes

AF:

0.00000400

AC:

AN:

250196

AF XY:

0.00

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.0000544

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000684

AC:

AN:

1461272

Hom.:

Cov.:

AF XY:

0.00000550

AC XY:

AN XY:

726954

show subpopulations

African (AFR)

AF:

0.0000896

AC:

AN:

33480

American (AMR)

AF:

0.00

AC:

AN:

44724

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26136

East Asian (EAS)

AF:

0.0000252

AC:

AN:

39700

South Asian (SAS)

AF:

0.0000116

AC:

AN:

86256

European-Finnish (FIN)

AF:

0.00

AC:

AN:

52820

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5768

European-Non Finnish (NFE)

AF:

0.00000450

AC:

AN:

1112002

Other (OTH)

AF:

0.00

AC:

AN:

60386

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.470

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:

0.0000263

AC:

AN:

152198

Hom.:

Cov.:

AF XY:

0.0000134

AC XY:

AN XY:

74354

show subpopulations

African (AFR)

AF:

0.0000241

AC:

AN:

41446

American (AMR)

AF:

0.0000654

AC:

AN:

15288

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3472

East Asian (EAS)

AF:

0.00

AC:

AN:

5182

South Asian (SAS)

AF:

0.00

AC:

AN:

4834

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10616

Middle Eastern (MID)

AF:

0.00

AC:

AN:

316

European-Non Finnish (NFE)

AF:

0.0000294

AC:

AN:

68040

Other (OTH)

AF:

0.00

AC:

AN:

2094

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.450

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Alfa

AF:

0.0000540

Hom.:

Bravo

AF:

0.0000113

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

LINK: link

Submissions by phenotype

Muscular dystrophy-dystroglycanopathy (congenital with brain and eye anomalies), type A14;C3809221:Muscular dystrophy-dystroglycanopathy (congenital with intellectual disability), type B14;C4518000:Autosomal recessive limb-girdle muscular dystrophy type 2T

Uncertain:1

Feb 10, 2022

Labcorp Genetics (formerly Invitae), Labcorp

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

This sequence change replaces arginine, which is basic and polar, with glutamine, which is neutral and polar, at codon 293 of the GMPPB protein (p.Arg293Gln). 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 GMPPB-related conditions. ClinVar contains an entry for this variant (Variation ID: 541077). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is not expected to disrupt GMPPB protein function. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site. 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

0.097

BayesDel_addAF

Benign

-0.11

BayesDel_noAF

Benign

-0.22

CADD

Benign

(source)

DANN

Uncertain

1.0

DEOGEN2

Uncertain

0.48

T;.;T

Eigen

Benign

-0.038

Eigen_PC

Benign

0.12

FATHMM_MKL

Uncertain

0.76

LIST_S2

Uncertain

0.92

.;D;D

M_CAP

Pathogenic

0.30

MetaRNN

Benign

0.26

T;T;T

MetaSVM

Uncertain

0.016

MutationAssessor

Benign

1.0

L;L;L

PhyloP100

3.3

PrimateAI

Benign

0.44

PROVEAN

Benign

-0.44

N;N;N

REVEL

Uncertain

0.34

Sift

Benign

0.29

T;T;T

Sift4G

Benign

0.40

T;T;T

Polyphen

0.19

B;B;B

Vest4

0.27

MutPred

0.41

Loss of MoRF binding (P = 0.0315);Loss of MoRF binding (P = 0.0315);Loss of MoRF binding (P = 0.0315);

MVP

0.89

MPC

0.63

ClinPred

0.24

GERP RS

5.0

Varity_R

0.088

gMVP

0.60

Mutation Taster

=75/25

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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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over