NM_000303.3:c.722_723delGTinsCG

Variant names:

• chr16-8847806-GT-CG
• NM_000303.3:c.722_723delGTinsCG
• PMM2 p.Cys241Ser

GermlineCancer (beta)

Variant summary

Our verdict is Uncertain significance.

+4 Uncertain · Hot

-7

-6

-1

0

+5

+6

+9

+10

BenignB

Likely BenignLB

UncertainVUS

Likely PathogenicLP

PathogenicP

The variant received 4 classification points (ACGS-UK Somatic Oncogenicity v2025). O3_ModerateO7_SupportingO8_Supporting

The NM_000303.3(PMM2):c.722_723delGTinsCG (p.Cys241Ser) variant causes a missense change. The gene PMM2 is a cancer driver gene (CancerMine: 2 driver citations). Note: allele frequency estimates from gnomAD may be inaccurate for this variant type (MNP or indel longer than 3 bp) due to technology limitations. The variant is absent from the gnomAD population database at sites with sufficient sequencing coverage. The affected nucleotide is highly conserved across species (PhyloP 100-way vertebrate score: 8.25). No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. A different missense at the same amino acid position has been reported as Pathogenic/Likely Pathogenic in ClinVar: p.C241R: Likely_pathogenic (ClinVar VariationId 2847057, 1 star) This exact variant is curated in the UniProt human variants database as Uncertain Significance.

• Frequency: Genomes: not found (cov: 33)
• Consequence: PMM2 NM_000303.3 missense
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 8.25
• Publications: 0 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), Natera, PanelApp Australia, Orphanet, ClinGen
• hyperinsulinemic hypoglycemia with polycystic kidney disease

  Inheritance: AR Classification: STRONG, MODERATE Submitted by: PanelApp Australia, ClinGen

ENSG00000260350 (HGNC:58482): ()

Classification according to ACGS-UK Somatic Oncogenicity v2025

Classification was made for transcript:

Our verdict: Uncertain_significance. The variant received 4 points.

Apply	Criterion Code & Title / Strength	Strength	Rationale / Clinical Context
	O3Absent or very rare in population		Absent or extremely rare in gnomAD (AC ≤ 2) — O3 moderate; GnomAD: AF = absent, AC = 0 — absent/extremely rare (O3 moderate [+2])
	O7Mutational hotspot or critical domain		Supporting: cancerhotspots.org hit, critical domain, or missense neighbourhood hotspot; No cancerhotspots.org hit at this position; UniProt domain: 0 pathogenic, 0 benign.; ±8 AA neighbourhood: 8 pathogenic, 1 benign (OR vs. background: 28.3); Variant does not impact splicing — splice-hotspot path not applicable
	O8Missense constraint in gene or region		Missense in gene/domain constrained for missense variation where missense is common disease mechanism (O8 supporting); Gene/disease mechanism: missense is a common mechanism of oncogenesis; gnomAD missense Z-score: -1.80 (threshold ≥3.09 for constraint); Domain-level constraint: variant is in a critically constrained functional domain (IS_AT_CRITICAL_DOMAIN)

Variant Effect in Transcripts

Automated classification analysis was done for transcript: NM_000303.3. You can select a different transcript below to see updated classification assignments.

RefSeq Transcripts

Sel.	Gene / Transcript	Tags	HGVSc / HGVSp	Effect	Exon rank	Protein / UniProt
	PMM2 NM_000303.3	MANE Select	c.722_723delGTinsCG p.Cys241Ser	missense	N/A	Prot: NP_000294.1 UniProt:

PMM2 NM_000303.3

MANE Select

HGVSc / HGVSpc.722_723delGTinsCGp.Cys241Ser

Exon rankN/A

missense

Prot: NP_000294.1UniProt: O15305-1A0A0S2Z4J6

Ensembl Transcripts

Sel.	Gene / Transcript	Tags	HGVSc / HGVSp	Effect	Exon rank	Protein / UniProt
	PMM2 ENST00000268261.9	TSL:1MANE Select	c.722_723delGTinsCG p.Cys241Ser	missense	N/A	Prot: ENSP00000268261.4 UniProt:
	PMM2 ENST00000565221.5	TSL:1	n.*340_*341delGTinsCG	3_prime_UTR	Exon 6 of 6	Prot: ENSP00000457932.1 UniProt:
	PMM2 ENST00000566540.5	TSL:1	n.*344_*345delGTinsCG	3_prime_UTR	Exon 6 of 6	Prot: ENSP00000454284.1 UniProt:

PMM2 ENST00000268261.9

TSL:1MANE Select

HGVSc / HGVSpc.722_723delGTinsCGp.Cys241Ser

Exon rankN/A

missense

Prot: ENSP00000268261.4UniProt: O15305-1

PMM2 ENST00000565221.5

TSL:1

HGVSc / HGVSpn.*340_*341delGTinsCG

Exon rankExon 6 of 6

3_prime_UTR

Prot: ENSP00000457932.1UniProt: H3BV34

PMM2 ENST00000566540.5

TSL:1

HGVSc / HGVSpn.*344_*345delGTinsCG

Exon rankExon 6 of 6

3_prime_UTR

Prot: ENSP00000454284.1UniProt: H3BM92

Frequencies

Allele frequencies (AF), counts (AC/AN), homozygotes and coverage

Common (AF > 0.05 / Hom > 5)

Rare (AF ≤ 0.0001 / Hom ≤ 1)

Source / population	AF	AC	Hom	AN	Coverage
Global population databases 2 sources Large-scale international reference populations
GnomAD3 genomes	AF:	AC:	Hom:	AN:	Cov:33
GnomAD4 genome	AF:	AC:	Hom:	AN:	Cov:33

Showing 2 sources

ClinVar

Not reported in ClinVar

Computational Scores

Algorithm	Calibrated pred.	Score	Prediction
PhyloP100	Pathogenic	8.3

Showing 1 of 1 scores

Splicing Scores

No splicing scores have been computed for this variant.

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

MaxEntScan Visualizer can be used to analyze the impact of this mutation on the neighboring sequence.

MaveDB functional evidence

MaveDB is a public repository of laboratory assays that test the effect of thousands of variants at once — treat this as supporting research data and interpret it with great caution; it is not a clinical classification.

No MaveDB functional evidence found for this variant.

Other links and lift over

hg19: chr16-8941663;

ACMG debug oncogenicity

ACGS debug oncogenicity

ACMG debug germline

Submit to ClinVar