rs1553692045

Positions:

• chr3-49723295-A-G

Variant summary

Our verdict is Uncertain significance. Variant got 3 ACMG points: 3P and 0B. PM2 PP3

The NM_021971.4(GMPPB):​c.218T>C​(p.Ile73Thr) variant causes a missense change. The variant allele was found at a frequency of 0.000000684 in 1,461,866 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: GMPPB NM_021971.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 5.36

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]

ACMG classification

Verdict is Uncertain_significance. Variant got 3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.75

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GMPPB	NM_021971.4	c.218T>C	p.Ile73Thr	missense_variant	3/9	ENST00000308388.7
GMPPB	NM_013334.4	c.218T>C	p.Ile73Thr	missense_variant	3/8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GMPPB	ENST00000308388.7	c.218T>C	p.Ile73Thr	missense_variant	3/9	1	NM_021971.4	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461866 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 727230

Gnomad4 AFR exome AF: 0.00

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: 0.0000166

GnomAD4 genome Cov.: 33

Bravo AF: 0.0000151

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

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

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Aug 29, 2018

This sequence change replaces isoleucine with threonine at codon 73 of the GMPPB protein (p.Ile73Thr). The isoleucine residue is moderately conserved and there is a moderate physicochemical difference between isoleucine and threonine. This variant is not present in population databases (ExAC no frequency). This variant has not been reported in the literature in individuals with GMPPB-related disease. Algorithms developed to predict the effect of missense changes on protein structure and function do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Benign"; Align-GVGD: "Class C25"). 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	Pathogenic	0.88
BayesDel_addAF	Pathogenic	0.32	D
BayesDel_noAF	Pathogenic	0.22
CADD	Uncertain	24
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.86	D;.;D
Eigen	Uncertain	0.23
Eigen_PC	Uncertain	0.31
FATHMM_MKL	Pathogenic	0.97	D
M_CAP	Uncertain	0.23	D
MetaRNN	Pathogenic	0.75	D;D;D
MetaSVM	Uncertain	-0.25	T
MutationAssessor	Uncertain	2.2	M;M;M
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Pathogenic	0.82	D
PROVEAN	Uncertain	-3.5	D;D;D
REVEL	Pathogenic	0.73
Sift	Benign	0.059	T;T;T
Sift4G	Uncertain	0.049	D;D;D
Polyphen		0.56	P;B;P
Vest4		0.66
MutPred		0.71		Loss of stability (P = 0.0123);Loss of stability (P = 0.0123);Loss of stability (P = 0.0123);
MVP		0.79
MPC		0.84
ClinPred		0.96	D
GERP RS		4.8
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.43
gMVP		0.74

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		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: rs1553692045; hg19: chr3-49760728;