NM_176812.5:c.481G>C

Variant names:

• chr20-33851064-G-C
• rs118203966
• NM_176812.5:c.481G>C

Variant summary

Our verdict is Likely pathogenic. The variant received 6 ACMG points: 6P and 0B. PM2 PM5 PP2 PP3

The NM_176812.5(CHMP4B):​c.481G>C​(p.Glu161Gln) variant causes a missense, splice region change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. 2/3 splice prediction tools predicting alterations to normal splicing. 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. E161K) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 33)
• Consequence: CHMP4B NM_176812.5 missense, splice_region
• Scores: Splicing: ADA: 0.9715
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 10.0
• Publications: 0 publications found

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]

CHMP4B Gene-Disease associations (from GenCC):

• cataract 31 multiple types

  Inheritance: AD Classification: STRONG, MODERATE Submitted by: Ambry Genetics, G2P, Labcorp Genetics (formerly Invitae)
• early-onset posterior polar cataract

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• early-onset posterior subcapsular cataract

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Likely_pathogenic. The variant received 6 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr20-33851064-G-A is described in ClinVar as [Pathogenic]. Clinvar id is 1086.Status of the report is no_assertion_criteria_provided, 0 stars.
• PP2: Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 3 curated pathogenic missense variants (we use a threshold of 10). The gene has 0 curated benign missense variants. Gene score misZ: 2.3781 (below the threshold of 3.09). Trascript score misZ: 2.8898 (below the threshold of 3.09). GenCC associations: The gene is linked to early-onset posterior subcapsular cataract, cataract 31 multiple types, early-onset posterior polar cataract.
• PP3: Splicing predictors support a deleterious effect. Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF. No scorers claiming Uncertain. Scorers claiming Benign: max_spliceai.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
CHMP4B	NM_176812.5	c.481G>C	p.Glu161Gln	missense_variant, splice_region_variant	Exon 3 of 5	ENST00000217402.3	NP_789782.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
CHMP4B	ENST00000217402.3	c.481G>C	p.Glu161Gln	missense_variant, splice_region_variant	Exon 3 of 5	1	NM_176812.5	ENSP00000217402.2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 25

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Cataract 31 multiple types Uncertain:1

Mar 21, 2021

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces glutamic acid with glutamine at codon 161 of the CHMP4B protein (p.Glu161Gln). The glutamic acid residue is highly conserved and there is a small physicochemical difference between glutamic acid and glutamine. This variant is not present in population databases (ExAC no frequency). This variant has been observed in individual(s) with congenital cataracts (Invitae). Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). This variant disrupts the p.Glu161 amino acid residue in CHMP4B. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 17701905). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. 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	0.88
BayesDel_addAF	Pathogenic	0.29	D
BayesDel_noAF	Pathogenic	0.19
CADD	Pathogenic	34
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.90	D
Eigen	Pathogenic	1.2
Eigen_PC	Pathogenic	1.1
FATHMM_MKL	Pathogenic	1.0	D
LIST_S2	Benign	0.82	T
M_CAP	Uncertain	0.15	D
MetaRNN	Pathogenic	0.90	D
MetaSVM	Pathogenic	0.84	D
MutationAssessor	Pathogenic	4.2	H
PhyloP100		10
PrimateAI	Pathogenic	0.86	D
PROVEAN	Uncertain	-2.6	D
REVEL	Uncertain	0.64
Sift	Uncertain	0.0020	D
Sift4G	Uncertain	0.0030	D
Polyphen		1.0	D
Vest4		0.81
MutPred		0.68		Loss of helix (P = 0.0626);
MVP		0.94
MPC		2.4
ClinPred		1.0	D
GERP RS		6.0
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.85
gMVP		0.69
Mutation Taster		=53/47	polymorphism

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	0.97
dbscSNV1_RF	Pathogenic	0.79
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

Other links and lift over

dbSNP: rs118203966; hg19: chr20-32438870;