rs769648248

Positions:

• chr16-8804793-C-G
• chr16-8804793-C-T

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM1 PM2 PM5

The NM_000303.3(PMM2):​c.205C>G​(p.Pro69Ala) variant causes a missense change. The variant allele was found at a frequency of 0.000000684 in 1,461,056 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. P69S) has been classified as Pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: PMM2 NM_000303.3 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 3.94

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 Likely_pathogenic. Variant got 6 ACMG points.

• PM1: In a chain Phosphomannomutase 2 (size 244) in uniprot entity PMM2_HUMAN there are 79 pathogenic changes around while only 2 benign (98%) 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 chr16-8804793-C-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
PMM2	NM_000303.3	c.205C>G	p.Pro69Ala	missense_variant	3/8	ENST00000268261.9	NP_000294.1
PMM2	XM_047434215.1	c.7-1523C>G		intron_variant			XP_047290171.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
PMM2	ENST00000268261.9	c.205C>G	p.Pro69Ala	missense_variant	3/8	1	NM_000303.3	ENSP00000268261.4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461056 Hom.: 0 Cov.: 29 AF XY: 0.00 AC XY: 0 AN XY: 726868

Gnomad4 AFR exome AF: 0.0000299

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: 0.00

GnomAD4 genome Cov.: 32

TwinsUK AF: 0.00 AC: 0

ALSPAC AF: 0.000259 AC: 1

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Apr 19, 2024

Variant summary: PMM2 c.205C>G (p.Pro69Ala) results in a non-conservative amino acid change in the encoded protein sequence. Three of five in-silico tools predict a damaging effect of the variant on protein function. The variant was absent in 251392 control chromosomes. The available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. To our knowledge, no occurrence of c.205C>G in individuals affected with Congenital Disorder Of Glycosylation Type 1a and no experimental evidence demonstrating its impact on protein function have been reported. No submitters have cited clinical-significance assessments for this variant to ClinVar. Based on the evidence outlined above, the variant was classified as uncertain significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.12
BayesDel_addAF	Pathogenic	0.17	D
BayesDel_noAF	Uncertain	0.010
CADD	Benign	18
DANN	Benign	0.26
DEOGEN2	Uncertain	0.49	T;D
Eigen	Benign	-0.41
Eigen_PC	Benign	-0.13
FATHMM_MKL	Uncertain	0.81	D
LIST_S2	Uncertain	0.88	D;D
M_CAP	Benign	0.025	T
MetaRNN	Uncertain	0.52	D;D
MetaSVM	Uncertain	0.0032	D
MutationAssessor	Benign	-0.80	.;N
PrimateAI	Benign	0.45	T
PROVEAN	Benign	1.1	N;N
REVEL	Uncertain	0.40
Sift	Benign	0.89	T;T
Sift4G	Benign	0.96	T;T
Polyphen		0.0010	.;B
Vest4		0.51
MutPred		0.70		.;Gain of catalytic residue at P69 (P = 0.0553);
MVP		0.85
MPC		0.0079
ClinPred		0.54	D
GERP RS		4.9
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.30
gMVP		0.85

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.18		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: rs769648248; hg19: chr16-8898650;