16-8847761-C-T

Variant summary

Our verdict is Pathogenic. Variant got 12 ACMG points: 12P and 0B. PM1 PM2 PM5 PP3_Strong PP5_Moderate

The NM_000303.3(PMM2):c.677C>T(p.Thr226Ile) variant causes a missense change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. T226S) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: PMM2 NM_000303.3 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P: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]

(HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 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, 8 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 chr16-8847761-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.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.96
• PP5: Variant 16-8847761-C-T is Pathogenic according to our data. Variant chr16-8847761-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 1916069.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
PMM2	NM_000303.3	c.677C>T	p.Thr226Ile	missense_variant	8/8	ENST00000268261.9
PMM2	XM_047434215.1	c.428C>T	p.Thr143Ile	missense_variant	6/6

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
PMM2	ENST00000268261.9	c.677C>T	p.Thr226Ile	missense_variant	8/8	1	NM_000303.3	P1
	ENST00000567942.1	n.319G>A		non_coding_transcript_exon_variant	2/2	3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

PMM2-congenital disorder of glycosylation Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Invitae

Nov 29, 2022

This variant disrupts the p.Thr226 amino acid residue in PMM2. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 10922383, 11156536, 17166182). 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. 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. This variant has not been reported in the literature in individuals affected with PMM2-related conditions. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces threonine, which is neutral and polar, with isoleucine, which is neutral and non-polar, at codon 226 of the PMM2 protein (p.Thr226Ile). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.47
BayesDel_addAF	Pathogenic	0.53	D
BayesDel_noAF	Pathogenic	0.52
Cadd	Uncertain	24
Dann	Uncertain	0.99
DEOGEN2	Pathogenic	0.82	D;D;.
Eigen	Uncertain	0.54
Eigen_PC	Uncertain	0.44
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Uncertain	0.96	D;D;D
M_CAP	Uncertain	0.17	D
MetaRNN	Pathogenic	0.96	D;D;D
MetaSVM	Pathogenic	1.1	D
MutationTaster	Benign	1.0	D;D;D;D;D
PrimateAI	Uncertain	0.63	T
PROVEAN	Pathogenic	-5.6	D;D;D
Sift	Benign	0.052	T;D;D
Sift4G	Uncertain	0.048	D;D;D
Polyphen		0.95	.;P;.
Vest4		0.90
MutPred		0.73		.;Loss of disorder (P = 0.0493);.;
MVP		0.97
MPC		0.042
ClinPred		0.97	D
GERP RS		5.2
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.80
gMVP		0.90

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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;