chr16-8847761-C-G

Position:

• chr16-8847761-C-G

Variant summary

Our verdict is Pathogenic. Variant got 16 ACMG points: 16P and 0B. PM1 PM2 PP3_Strong PP5_Very_Strong

The NM_000303.3(PMM2):​c.677C>G​(p.Thr226Ser) variant causes a missense change. The variant allele was found at a frequency of 0.00000137 in 1,461,694 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 Likely pathogenic (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: PMM2 NM_000303.3 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:4 O:1
• Conservation: PhyloP100: 6.55

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 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 16 ACMG points.

• PM1: In a binding_site (size 0) in uniprot entity PMM2_HUMAN
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.985
• PP5: Variant 16-8847761-C-G is Pathogenic according to our data. Variant chr16-8847761-C-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 7722.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr16-8847761-C-G is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
PMM2	NM_000303.3	c.677C>G	p.Thr226Ser	missense_variant	8/8	ENST00000268261.9	NP_000294.1
PMM2	XM_047434215.1	c.428C>G	p.Thr143Ser	missense_variant	6/6		XP_047290171.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
PMM2	ENST00000268261.9	c.677C>G	p.Thr226Ser	missense_variant	8/8	1	NM_000303.3	ENSP00000268261.4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251300 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 135846

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000880

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461694 Hom.: 0 Cov.: 30 AF XY: 0.00000138 AC XY: 1 AN XY: 727166

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: 8.99e-7

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome Cov.: 32

ExAC AF: 0.00000824 AC: 1

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:4 Other:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

PMM2-congenital disorder of glycosylation Pathogenic:4 Other:1

not provided, no classification provided	literature only	GeneReviews	-	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Apr 01, 2022	Variant summary: PMM2 c.677C>G (p.Thr226Ser) results in a conservative amino acid change in the encoded protein sequence. Four of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 4e-06 in 251300 control chromosomes. c.677C>G has been reported in the literature as compound heterozygous genotypes in individuals affected with Congenital Disorder Of Glycosylation Type 1a (example, Vuillaumier-Barrot_2000, de Lonlay_2001, Briones_2002, Quelhas_2021). These data indicate that the variant is likely to be associated with disease. At least one publication reports experimental evidence evaluating an impact on protein function example, Vuillaumier-Barrot_2000). The most pronounced variant effect results in 10%-<30% of normal Phosphomannomutase enzyme activity in-vitro. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014. Based on the evidence outlined above, the variant was classified as likely pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	Baylor Genetics	Nov 22, 2023	- -
Pathogenic, no assertion criteria provided	literature only	OMIM	Aug 01, 2000	- -
Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Dec 03, 2021	Experimental studies have shown that this missense change affects PMM2 function (PMID: 10922383). Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Benign"; Align-GVGD: "Class C55"). ClinVar contains an entry for this variant (Variation ID: 7722). This missense change has been observed in individual(s) with PMM2-related conditions (PMID: 10922383, 11156536, 17166182). This variant is present in population databases (rs80338706, gnomAD 0.0009%). This sequence change replaces threonine, which is neutral and polar, with serine, which is neutral and polar, at codon 226 of the PMM2 protein (p.Thr226Ser). For these reasons, this variant has been classified as Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.67
BayesDel_addAF	Pathogenic	0.55	D
BayesDel_noAF	Pathogenic	0.55
CADD	Uncertain	24
DANN	Uncertain	0.99
DEOGEN2	Pathogenic	0.91	D;D;.
Eigen	Uncertain	0.58
Eigen_PC	Uncertain	0.47
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.97	D;D;D
M_CAP	Pathogenic	0.31	D
MetaRNN	Pathogenic	0.98	D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	4.0	.;H;.
PrimateAI	Uncertain	0.53	T
PROVEAN	Uncertain	-3.9	D;D;D
REVEL	Pathogenic	0.88
Sift	Uncertain	0.0010	D;D;D
Sift4G	Uncertain	0.0020	D;D;D
Polyphen		0.97	.;D;.
Vest4		0.94
MutPred		0.86		.;Gain of disorder (P = 0.0605);.;
MVP		0.98
MPC		0.016
ClinPred		0.99	D
GERP RS		5.2
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.90
gMVP		0.82

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: rs80338706; hg19: chr16-8941618;