chr3-49721818-G-A

Variant names:

Variant summary

Our verdict is Benign. The variant received -17 ACMG points: 0P and 17B. BP4_StrongBP6_Very_StrongBP7BS1

The NM_021971.4(GMPPB):c.1017C>T(p.Asn339Asn) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000209 in 1,613,260 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Likely benign (★★).

Frequency

Genomes: 𝑓 0.0010 ( 0 hom., cov: 33)

Exomes 𝑓: 0.00012 ( 0 hom. )

Consequence

GMPPB
NM_021971.4 synonymous

Scores

Clinical Significance

Likely benign criteria provided, multiple submitters, no conflicts B:5

Conservation

PhyloP100: -0.424

Publications

0 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: Benign. The variant received -17 ACMG points.

BP4

Computational evidence support a benign effect (BayesDel_noAF=-0.57).

BP6

Variant 3-49721818-G-A is Benign according to our data. Variant chr3-49721818-G-A is described in ClinVar as Likely_benign. ClinVar VariationId is 391583.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

BP7

Synonymous conserved (PhyloP=-0.424 with no splicing effect.

BS1

Variant frequency is greater than expected in population afr. GnomAd4 allele frequency = 0.00103 (157/152312) while in subpopulation AFR AF = 0.00366 (152/41566). AF 95% confidence interval is 0.00318. There are 0 homozygotes in GnomAd4. There are 73 alleles in the male GnomAd4 subpopulation. Median coverage is 33. This position passed quality control check.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_021971.4. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	GMPPB	NM_021971.4	MANE Select	c.1017C>T	p.Asn339Asn	synonymous	Exon 9 of 9	NP_068806.2
	GMPPB	NM_013334.4		c.1098C>T	p.Asn366Asn	synonymous	Exon 8 of 8	NP_037466.3

Ensembl Transcripts

Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein
GMPPB	ENST00000308388.7	TSL:1 MANE Select	c.1017C>T	p.Asn339Asn	synonymous	Exon 9 of 9	ENSP00000311130.6
GMPPB	ENST00000495627.2	TSL:2	c.1125C>T	p.Asn375Asn	synonymous	Exon 9 of 9	ENSP00000503768.1
GMPPB	ENST00000308375.10	TSL:2	c.1098C>T	p.Asn366Asn	synonymous	Exon 8 of 8	ENSP00000309092.6

Frequencies

GnomAD3 genomes

AF:

0.00101

AC:

154

AN:

152194

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00360

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.000131

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.000193

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:

0.000267

AC:

AN:

250556

AF XY:

0.000177

show subpopulations

Gnomad AFR exome

AF:

0.00277

Gnomad AMR exome

AF:

0.000289

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.000163

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.0000440

Gnomad OTH exome

AF:

0.000653

GnomAD4 exome

AF:

0.000123

AC:

180

AN:

1460948

Hom.:

Cov.:

AF XY:

0.0000991

AC XY:

AN XY:

726870

show subpopulations

African (AFR)

AF:

0.00412

AC:

138

AN:

33480

American (AMR)

AF:

0.000224

AC:

AN:

44724

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26136

East Asian (EAS)

AF:

0.000101

AC:

AN:

39700

South Asian (SAS)

AF:

0.0000116

AC:

AN:

86258

European-Finnish (FIN)

AF:

0.00

AC:

AN:

52554

Middle Eastern (MID)

AF:

0.000173

AC:

AN:

5768

European-Non Finnish (NFE)

AF:

0.0000144

AC:

AN:

1111944

Other (OTH)

AF:

0.000166

AC:

AN:

60384

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.486

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:

0.00103

AC:

157

AN:

152312

Hom.:

Cov.:

AF XY:

0.000980

AC XY:

AN XY:

74464

show subpopulations

African (AFR)

AF:

0.00366

AC:

152

AN:

41566

American (AMR)

AF:

0.000131

AC:

AN:

15300

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3472

East Asian (EAS)

AF:

0.000193

AC:

AN:

5180

South Asian (SAS)

AF:

0.00

AC:

AN:

4830

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10610

Middle Eastern (MID)

AF:

0.00

AC:

AN:

294

European-Non Finnish (NFE)

AF:

0.0000294

AC:

AN:

68034

Other (OTH)

AF:

0.00

AC:

AN:

2114

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.490

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:

0.000662

Hom.:

Bravo

AF:

0.00122

Asia WGS

AF:

0.000577

AC:

AN:

3478

EpiCase

AF:

0.000109

EpiControl

AF:

0.0000593

ClinVar

Significance: Likely benign

Submissions summary: Benign:5

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

not provided

Benign:3

Aug 01, 2025

CeGaT Center for Human Genetics Tuebingen

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

GMPPB: BP4, BP7

Oct 13, 2020

GeneDx

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Breakthrough Genomics, Breakthrough Genomics

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:not provided

not specified

Benign:1

Aug 09, 2016

Genetic Services Laboratory, University of Chicago

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

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

Benign:1

Jan 28, 2025

Labcorp Genetics (formerly Invitae), Labcorp

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Computational scores

Source: dbNSFP v4.9

Name

Calibrated prediction

Score

Prediction

BayesDel_noAF

Benign

-0.57

CADD

Benign

1.6

(source)

DANN

Benign

0.88

PhyloP100

-0.42

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

Variant Effect in Transcripts

RefSeq Transcripts

Ensembl Transcripts

Frequencies

Age Distribution

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over