20-33848476-A-G

Variant names:

• chr20-33848476-A-G
• NM_176812.5:c.200A>G

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PM2 PP5_Moderate

The NM_176812.5(CHMP4B):​c.200A>G​(p.Gln67Arg) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Likely pathogenic (★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: CHMP4B NM_176812.5 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 7.29

Genes affected

CHMP4B (HGNC:16171): (charged multivesicular body protein 4B) This gene encodes a member of the chromatin-modifying protein/charged multivesicular body protein (CHMP) protein family. The protein is part of the endosomal sorting complex required for transport (ESCRT) complex III (ESCRT-III), which functions in the sorting of endocytosed cell-surface receptors into multivesicular endosomes. The ESCRT machinery also functions in the final abscisson stage of cytokinesis and in the budding of enveloped viruses such as HIV-1. The three proteins of the CHMP4 subfamily interact with programmed cell death 6 interacting protein (PDCD6IP, also known as ALIX), which also functions in the ESCRT pathway. The CHMP4 proteins assemble into membrane-attached 5-nm filaments that form circular scaffolds and promote or stabilize outward budding. These polymers are proposed to help generate the luminal vesicles of multivesicular bodies. Mutations in this gene result in autosomal dominant posterior polar cataracts.[provided by RefSeq, Oct 2009]

ACMG classification

Verdict is Uncertain_significance. Variant got 4 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 20-33848476-A-G is Pathogenic according to our data. Variant chr20-33848476-A-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 2841293.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
CHMP4B	NM_176812.5	c.200A>G	p.Gln67Arg	missense_variant	Exon 2 of 5	ENST00000217402.3	NP_789782.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
CHMP4B	ENST00000217402.3	c.200A>G	p.Gln67Arg	missense_variant	Exon 2 of 5	1	NM_176812.5	ENSP00000217402.2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Cataract 31 multiple types Pathogenic:1

Apr 11, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces glutamine, which is neutral and polar, with arginine, which is basic and polar, at codon 67 of the CHMP4B protein (p.Gln67Arg). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with clinical features of congenital cataracts (Invitae). In at least one individual the variant was observed to be de novo. An algorithm developed to predict the effect of missense changes on protein structure and function (PolyPhen-2) suggests that this variant  is likely to be tolerated. 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.85
BayesDel_addAF	Uncertain	0.040	T
BayesDel_noAF	Benign	-0.18
CADD	Uncertain	25
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.63	D
Eigen	Uncertain	0.27
Eigen_PC	Uncertain	0.41
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.95	D
M_CAP	Benign	0.036	D
MetaRNN	Uncertain	0.47	T
MetaSVM	Benign	-0.47	T
MutationAssessor	Benign	1.6	L
PrimateAI	Pathogenic	0.85	D
PROVEAN	Uncertain	-2.6	D
REVEL	Uncertain	0.32
Sift	Benign	0.074	T
Sift4G	Benign	0.10	T
Polyphen		0.22	B
Vest4		0.64
MutPred		0.49		Gain of methylation at Q67 (P = 0.0223);
MVP		0.81
MPC		1.5
ClinPred		0.92	D
GERP RS		5.8
Varity_R		0.87
gMVP		0.74

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

No publications associated with this variant yet.

Other links and lift over

hg19: chr20-32436282;