16-8811648-T-G

Variant names:

• chr16-8811648-T-G
• rs150577656
• NM_000303.3:c.458T>G

Variant summary

Our verdict is Pathogenic. The variant received 12 ACMG points: 12P and 0B. PM1 PM2 PM5 PP2 PP3_Strong PP5

The NM_000303.3(PMM2):​c.458T>G​(p.Ile153Arg) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.0000048 in 1,459,026 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 Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. I153T) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000048 (0 hom.)
• Consequence: PMM2 NM_000303.3 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2 U:1
• Conservation: PhyloP100: 7.78
• Publications: 12 publications found

Genes affected

PMM2 (HGNC:9115): (phosphomannomutase 2) The protein encoded by this gene catalyzes the isomerization of mannose 6-phosphate to mannose 1-phosphate, which is a precursor to GDP-mannose necessary for the synthesis of dolichol-P-oligosaccharides. Mutations in this gene have been shown to cause defects in glycoprotein biosynthesis, which manifests as carbohydrate-deficient glycoprotein syndrome type I. [provided by RefSeq, Jul 2008]

PMM2 Gene-Disease associations (from GenCC):

• congenital disorder of glycosylation type I

  Inheritance: AR Classification: DEFINITIVE Submitted by: Myriad Women’s Health
• PMM2-congenital disorder of glycosylation

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: G2P, Labcorp Genetics (formerly Invitae), Orphanet, PanelApp Australia, ClinGen

ACMG classification

Our verdict: Pathogenic. The variant received 12 ACMG points.

• PM1: In a hotspot region, there are 5 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 9 uncertain in NM_000303.3
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr16-8811648-T-C is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 371406.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP2: Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 89 curated pathogenic missense variants (we use a threshold of 10). The gene has 24 curated benign missense variants. Gene score misZ: -1.3872 (below the threshold of 3.09). Trascript score misZ: -1.8083 (below the threshold of 3.09). GenCC associations: The gene is linked to PMM2-congenital disorder of glycosylation, congenital disorder of glycosylation type I.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.973
• PP5: Variant 16-8811648-T-G is Pathogenic according to our data. Variant chr16-8811648-T-G is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 1422606.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000303.3. 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
	PMM2	NM_000303.3	MANE Select	c.458T>G	p.Ile153Arg	missense	Exon 6 of 8	NP_000294.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	PMM2	ENST00000268261.9	TSL:1 MANE Select	c.458T>G	p.Ile153Arg	missense	Exon 6 of 8	ENSP00000268261.4
	PMM2	ENST00000565221.5	TSL:1	n.*76T>G		non_coding_transcript_exon	Exon 4 of 6	ENSP00000457932.1
	PMM2	ENST00000566540.5	TSL:1	n.*80T>G		non_coding_transcript_exon	Exon 4 of 6	ENSP00000454284.1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD2 exomes AF: 0.00000398 AC: 1 AN: 251354 AF XY: 0.00000736

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000289

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000480 AC: 7 AN: 1459026 Hom.: 0 Cov.: 29 AF XY: 0.00000275 AC XY: 2 AN XY: 726044

African (AFR) AF: 0.00 AC: 0 AN: 33422

American (AMR) AF: 0.00 AC: 0 AN: 44720

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26104

East Asian (EAS) AF: 0.00 AC: 0 AN: 39666

South Asian (SAS) AF: 0.00 AC: 0 AN: 86192

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53392

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5766

European-Non Finnish (NFE) AF: 0.00000541 AC: 6 AN: 1109464

Other (OTH) AF: 0.0000166 AC: 1 AN: 60300

GnomAD4 genome Cov.: 33

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

PMM2-congenital disorder of glycosylation Pathogenic:2 Uncertain:1

Jul 15, 2022

Center for Genomics, Ann and Robert H. Lurie Children's Hospital of Chicago

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant has not been reported in the literature and is not present in large control databases. This variant is present in ClinVar (Variation ID:1422606). Evolutionary conservation and computational predictive tools suggest that this variant may impact the protein. Of note, other variants at this position have been reported in association with disease (p.Ile153Met, p.Ile153Thr) supporting the potential functional relevance of this codon. In summary, data on this variant is highly suspicious for disease, but requires further evidence for pathogenicity. Therefore, the clinical significance of this variant is uncertain.

Sep 08, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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 expected to disrupt PMM2 protein function. ClinVar contains an entry for this variant (Variation ID: 1422606). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site. This variant disrupts the p.Ile153 amino acid residue in PMM2. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 11058895, 11156536, 25497157, 26502900). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. This sequence change replaces isoleucine, which is neutral and non-polar, with arginine, which is basic and polar, at codon 153 of the PMM2 protein (p.Ile153Arg). This variant is present in population databases (no rsID available, gnomAD 0.003%). This variant has not been reported in the literature in individuals affected with PMM2-related conditions.

Oct 19, 2020

Victorian Clinical Genetics Services, Murdoch Childrens Research Institute

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Based on the classification scheme VCGS_Germline_v1.3.2, this variant is classified as Likely Pathogenic. Following criteria are met: 0102 - Loss of function is a known mechanism of disease in this gene and is associated with PMM2-congenital disorder of glycosylation (PMM2-CDG). (I) 0106 - This gene is associated with autosomal recessive disease. (I) 0200 - Variant is predicted to result in a missense amino acid change from isoleucine to arginine (exon 6). (I) 0251 - This variant is heterozygous. (I) 0304 - Variant is present in gnomAD v2 <0.01 for a recessive condition (1 heterozygote, 0 homozygotes). (SP) 0309 - An alternative amino acid change at the same position has been observed in gnomAD (v2) (4 heterozygotes, 0 homozygotes). (I) 0501 - Missense variant consistently predicted to be damaging by multiple in silico tools or highly conserved with a major amino acid change. (SP) 0600 - Variant is located in the annotated PMM domain (NCBI, Decipher, PDB). (I) 0704 - Another missense variant comparable to the one identified in this case has limited previous evidence for pathogenicity. A different variant in the same codon resulting in a change to a threonine has been shown to cause PMM2-CDG (ClinVar, PMID: 26502900, 30991241). (SP) 0807 - This variant has no previous evidence of pathogenicity. (I) 0905 - No published segregation evidence has been identified for this variant. (I) 1007 - No published functional evidence has been identified for this variant. (I) 1102 - Strong phenotype match for this individual. (SP) 1201 - Heterozygous variant detected in trans with a second pathogenic heterozygous variant, p.(Val231Met) in a recessive disease. (SP) 1205 - This variant has been shown to be maternally inherited (VCGS #20G001740). (I) Legend: (SP) - Supporting pathogenic, (I) - Information, (SB) - Supporting benign

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.81
BayesDel_addAF	Pathogenic	0.44	D
BayesDel_noAF	Pathogenic	0.47
CADD	Pathogenic	33
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.85	D
Eigen	Pathogenic	0.85
Eigen_PC	Pathogenic	0.77
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Pathogenic	0.99	D
M_CAP	Pathogenic	0.63	D
MetaRNN	Pathogenic	0.97	D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.7	H
PhyloP100		7.8
PrimateAI	Uncertain	0.61	T
PROVEAN	Pathogenic	-6.6	D
REVEL	Pathogenic	0.90
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0	D
Polyphen		1.0	D
Vest4		0.84
MutPred		0.85		Gain of disorder (P = 0.0062)
MVP		0.99
MPC		0.040
ClinPred		1.0	D
GERP RS		5.2
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.97
gMVP		0.95
Mutation Taster		=6/94	disease causing

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.27		Details are displayed if max score is > 0.2
DS_AG_spliceai		0.27		Position offset: -6

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Other links and lift over

dbSNP: rs150577656; hg19: chr16-8905505;