20-2660912-A-G

Position:

• chr20-2660912-A-G

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM2 PP3_Strong

The NM_006899.5(IDH3B):​c.395T>C​(p.Leu132Pro) variant causes a missense change. The variant allele was found at a frequency of 0.00000342 in 1,461,814 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 Uncertain significance (★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000034 (0 hom.)
• Consequence: IDH3B NM_006899.5 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter P:1 U:1
• Conservation: PhyloP100: 7.06

Genes affected

IDH3B (HGNC:5385): (isocitrate dehydrogenase (NAD(+)) 3 non-catalytic subunit beta) Isocitrate dehydrogenases catalyze the oxidative decarboxylation of isocitrate to 2-oxoglutarate. These enzymes belong to two distinct subclasses, one of which utilizes NAD(+) as the electron acceptor and the other NADP(+). Five isocitrate dehydrogenases have been reported: three NAD(+)-dependent isocitrate dehydrogenases, which localize to the mitochondrial matrix, and two NADP(+)-dependent isocitrate dehydrogenases, one of which is mitochondrial and the other predominantly cytosolic. NAD(+)-dependent isocitrate dehydrogenases catalyze the allosterically regulated rate-limiting step of the tricarboxylic acid cycle. Each isozyme is a heterotetramer that is composed of two alpha subunits, one beta subunit, and one gamma subunit. The protein encoded by this gene is the beta subunit of one isozyme of NAD(+)-dependent isocitrate dehydrogenase. Multiple alternatively spliced transcript variants encoding different isoforms have been described for this gene. [provided by RefSeq, Sep 2016]

IDH3B (HGNC:):

ACMG classification

Verdict is Likely_pathogenic. Variant got 6 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.983

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
IDH3B	NM_006899.5	c.395T>C	p.Leu132Pro	missense_variant	5/12	ENST00000380843.9	NP_008830.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
IDH3B	ENST00000380843.9	c.395T>C	p.Leu132Pro	missense_variant	5/12	1	NM_006899.5	ENSP00000370223.4
IDH3B	ENST00000474315.5	c.395T>C	p.Leu132Pro	missense_variant	5/13	1		ENSP00000482773.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251390 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 135868

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: 0.00000342 AC: 5 AN: 1461814 Hom.: 0 Cov.: 33 AF XY: 0.00000138 AC XY: 1 AN XY: 727218

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: 0.00000270

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Alfa AF: 0.0000458 Hom.: 0

ClinVar

Significance: Uncertain significance

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Retinitis pigmentosa 46 Pathogenic:1

Pathogenic, no assertion criteria provided

literature only

OMIM

Oct 01, 2008

- -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Dec 09, 2023

This sequence change replaces leucine, which is neutral and non-polar, with proline, which is neutral and non-polar, at codon 132 of the IDH3B protein (p.Leu132Pro). This variant is present in population databases (rs137853020, gnomAD no frequency). This missense change has been observed in individuals with retinitis pigmentosa (PMID: 18806796). ClinVar contains an entry for this variant (Variation ID: 5506). 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 IDH3B protein function with a positive predictive value of 80%. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.39	D
BayesDel_noAF	Pathogenic	0.32
CADD	Pathogenic	28
DANN	Pathogenic	1.0
DEOGEN2	Uncertain	0.61	D;.;D;D
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	0.98
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.93	D;D;D;D
M_CAP	Uncertain	0.16	D
MetaRNN	Pathogenic	0.98	D;D;D;D
MetaSVM	Uncertain	0.58	D
MutationAssessor	Pathogenic	4.5	.;H;H;.
PrimateAI	Pathogenic	0.81	D
PROVEAN	Pathogenic	-5.7	.;D;D;.
REVEL	Pathogenic	0.82
Sift	Pathogenic	0.0	.;D;D;.
Sift4G	Pathogenic	0.0010	D;D;D;D
Polyphen		1.0	.;D;D;.
Vest4		0.99
MutPred		0.94		Loss of stability (P = 0.0164);Loss of stability (P = 0.0164);Loss of stability (P = 0.0164);Loss of stability (P = 0.0164);
MVP		0.97
MPC		1.5
ClinPred		1.0	D
GERP RS		5.9
Varity_R		0.99
gMVP		0.97

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: rs137853020; hg19: chr20-2641558;