About IDH1
No gene-level summary was recorded for this case.
No variant summary was recorded for this case.
Five-step scale from benign to pathogenic. This variant is likely pathogenic. Select a step to read what it means.
Likely pathogenic.A likely pathogenic classification under the recorded framework.
Gene-level background from the recorded interpretation.
Words with a dotted underline have a short definition. Hover or tap them.No gene-level summary was recorded for this case.
The recorded framework is Not recorded. The criteria and strengths shown below come from the saved assessment; this page does not recalculate the classification.
The applied criteria and their strengths are shown as assessed under the stated framework.
The IDH1 R132S variant was directly tested in recombinant protein functional assays. Dang et al. (2009) generated purified recombinant R132S mutant IDH1 protein and demonstrated that R132S, like other R132 mutations, results in gain-of-function NADPH-dependent reduction of α-ketoglutarate to the oncometabolite (R)-2-hydroxyglutarate. The functional effect is unequivocal: the mutation alters enzymatic activity from oxidative decarboxylation of isocitrate to reductive production of 2-HG. A single study with direct variant-specific testing supports moderate-strength PS3.
The variant alters Arg132, the critical active-site residue of IDH1 responsible for isocitrate substrate binding and catalysis. This residue is located in the enzyme's catalytic domain and is a statistically significant mutational hotspot (cancerhotspots.org). All known oncogenic IDH1 mutations occur at this residue. The Arg132 position forms hydrogen bonds with the α- and β-carboxyl groups of isocitrate and is essential for normal enzymatic function.
This variant is completely absent from population databases. gnomAD v4.1 reports 0 alleles in 1,613,196 alleles across all populations (AF=0.000%). gnomAD v2.1 and gnomAD-Canada v1.0 also report complete absence. The allele frequency is well below the 0.1% threshold for PM2 under generic ACMG rules.
A different missense change at the same amino acid residue (p.Arg132) has been established as pathogenic. IDH1 p.Arg132His (R132H) is the most common and well-characterized pathogenic IDH1 variant in gliomas and other cancers. p.Arg132Cys (R132C) is also established as pathogenic. Both are listed as pathogenic in ClinVar and extensively characterized in the literature. The current variant, p.Arg132Ser, is a different amino acid change at the same residue.
Multiple in silico tools support a deleterious effect. REVEL score is 0.904 (strongly pathogenic prediction). SpliceAI predicts a possible splice impact with a maximum delta score of 0.61 (donor gain delta = 0.61, donor loss delta = 0.48). BayesDel score is 0.419 (moderate). The high REVEL score and moderate SpliceAI signal together provide supporting evidence for a deleterious effect.
No benign criterion marked as applied in the recorded assessment.
gene-specific framework lacked a usable explicit final combination framework, so generic ACMG/AMP 2015 final-combination rules were applied as fallback; applied criteria: PS3 moderate, PM1 moderate, PM2 moderate, PM5 moderate, PP3 supporting; combination = 4 moderate + 1 supporting, which maps to Likely Pathogenic.
Evidence summaries and captured source records, where available. Missing entries should not be interpreted as negative findings.
gnomAD v4.1: 0 / 1,613,196 alleles. Recorded AF 0. Recorded homozygote count 0.
Absent from gnomAD v2.1.
Absent from gnomAD-Canada v1.0.
Recorded SpliceAI maximum delta score: 0.610. Refer to the recorded PP3/BP4 rationale for interpretation.
1 Pathogenic. ClinVar API review status: criteria provided, single submitter.
OncoKB identified variant-specific curated literature and context relevant to functional review; curated oncogenicity label: Likely Oncogenic.
This variant has previously been reported in somatic cancers (COSMIC; COSV61615649, n = 217 times).
This variant lies in a statistically significant hotspot.
ACMG/AMP criteria under Not recorded, with the data and sources behind each one.
29 criteria with recorded statuses: 5 met · 17 not met · 2 not assessed · 5 not applicable. Open any row for the full reasoning, the rule and the evidence behind it.
IDH1 c.394C>A (p.Arg132Ser) is absent from population databases (gnomAD v4.1: 0/1,613,196 alleles).
The variant alters the critical active-site residue Arg132 of IDH1, a well-established mutational hotspot and functional domain essential for substrate binding and catalysis.
Different missense changes at the same residue (p.Arg132His, p.Arg132Cys) are established pathogenic variants, satisfying PM5.
Functional studies directly testing the R132S mutant protein demonstrate neomorphic gain-of-function activity: NADPH-dependent reduction of α-ketoglutarate to the oncometabolite (R)-2-hydroxyglutarate.
Multiple in silico tools support a deleterious effect, including a REVEL score of 0.904 and a SpliceAI max delta of 0.61.
ClinVar reports this variant as Pathogenic (VariationID 375893) based on a single clinical laboratory submission with criteria provided (1-star). This does not reach the 3-star expert panel threshold required for PP5.
The variant has been reported in somatic cancers (COSMIC: n=217), primary myelofibrosis (3/301 patients; PMID:21912393), and a case of adult medulloblastoma (PMID:24616312), consistent with oncogenicity but not meeting germline PS4 thresholds.
No criteria match.
No further detail was recorded.
No further detail was recorded.
No further detail was recorded.
No further detail was recorded.
Every interpreted variant in IDH1, mapped onto the exon structure of NM_005896.3. Select a row to find it on the plot.
| Protein | Location | Classification | Link |
|---|
This variant is present in gnomAD v4.1 (AF= 0; MAF= 0.00000%, 0/1613196 alleles, homozygotes = 0) and has highest observed frequency in the African/African American population (AF= 0; MAF= 0.00000%, 0/74792 alleles, homozygotes = 0).
Absent from gnomAD v2.1.
Absent from gnomAD-Canada v1.0.
No further detail was recorded.
SpliceAI predicts possible splice impact for this variant (max delta score = 0.61). REVEL score = 0.904. BayesDel score = 0.419369.
8 paper records listed. 2 cited in the classification.
Similar to R132H mutant protein, R132C, R132L, and R132S mutations all result in a gain-of-function for NADPH-dependent reduction of αKG.
Location Results section; Supplementary Figure 4; Methods Summary
Context Recombinant protein purification from E. coli; stopped-flow spectrophotometry enzyme assays; LC-MS metabolite detection; U87MG and LN-18 glioblastoma cell lines
IDH1 R132C/S/L/G/V 5%-8%
Location Table 1 (allele frequencies); text describing IDH1 R132C/S/L/G/V mutant alleles
Context Review article; no primary experimental data
The mutant IDH was detected in 12 patients (4%): 7 IDH2 (5 R140Q, 1 R140W and 1 R172G) and 5 IDH1 (3 R132S and 2 R132C).
Results, paragraph 1; Discussion
Both M3 and M13 samples contained a heterozygous IDH1 CGT>AGT R132S mutation.
Results, paragraph describing deep sequencing findings; Figure 3
Screenshots represent source records captured during evidence collection. Select one to view the recorded source content.
The evidence statements recorded by the interpretation pipeline. They have not been reinterpreted by the page.
This variant is present in gnomAD v4.1 (AF= 0; MAF= 0.00000%, 0/1613196 alleles, homozygotes = 0) and has highest observed frequency in the African/African American population (AF= 0; MAF= 0.00000%, 0/74792 alleles, homozygotes = 0).
Absent from gnomAD v2.1.
Absent from gnomAD-Canada v1.0.
This variant has been reported in ClinVar as Pathogenic (1 clinical laboratory). (ClinVarID = 375893)
SpliceAI predicts possible splice impact for this variant (max delta score = 0.61). REVEL score = 0.904. BayesDel score = 0.419369.
OncoKB identified variant-specific curated literature and context relevant to functional review; curated oncogenicity label: Likely Oncogenic.
This variant lies in a statistically significant hotspot. This variant has previously been reported in somatic cancers (COSMIC; COSV61615649, n = 217 times).
This variant lies in a statistically significant hotspot.