20-33852179-T-G

Variant summary

Our verdict is Likely benign. Variant got -4 ACMG points: 2P and 6B. PM1 BP4_Moderate BS2

The NM_176812.5(CHMP4B):c.586T>G(p.Ser196Ala) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000109 in 1,461,884 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 14/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: not found (cov: 31)
  • Exomes 𝑓: 0.000011 (0 hom.)
• Consequence: CHMP4B NM_176812.5 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 2.46

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 Likely_benign. Variant got -4 ACMG points.

• PM1: In a chain Charged multivesicular body protein 4b (size 222) in uniprot entity CHM4B_HUMAN there are 6 pathogenic changes around while only 0 benign (100%) in NM_176812.5
• BP4: Computational evidence support a benign effect (MetaRNN=0.23867133).
• BS2: High AC in GnomAdExome at 8 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
CHMP4B	NM_176812.5	c.586T>G	p.Ser196Ala	missense_variant	4/5	ENST00000217402.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
CHMP4B	ENST00000217402.3	c.586T>G	p.Ser196Ala	missense_variant	4/5	1	NM_176812.5	P1

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD3 exomes AF: 0.0000318 AC: 8 AN: 251496 Hom.: 0 AF XY: 0.0000294 AC XY: 4 AN XY: 135922

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: 0.0000703

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000109 AC: 16 AN: 1461884 Hom.: 0 Cov.: 32 AF XY: 0.0000124 AC XY: 9 AN XY: 727242

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: 0.0000144

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 31

Alfa AF: 0.0000312 Hom.: 0

Bravo AF: 0.0000113

ExAC AF: 0.0000494 AC: 6

EpiCase AF: 0.00

EpiControl AF: 0.000178

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Cataract 31 multiple types Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

May 02, 2019

This sequence change replaces serine with alanine at codon 196 of the CHMP4B protein (p.Ser196Ala). The serine residue is highly conserved and there is a moderate physicochemical difference between serine and alanine. This variant is present in population databases (rs765835212, ExAC 0.009%). This variant has not been reported in the literature in individuals with CHMP4B-related conditions. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be tolerated, but these predictions have not been confirmed by published functional studies and their clinical significance is uncertain. 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	Benign	0.083
BayesDel_addAF	Benign	-0.20	T
BayesDel_noAF	Benign	-0.34
Cadd	Benign	20
Dann	Uncertain	0.99
DEOGEN2	Benign	0.39	T
Eigen	Benign	-0.063
Eigen_PC	Benign	0.11
FATHMM_MKL	Uncertain	0.97	D
LIST_S2	Benign	0.85	T
M_CAP	Benign	0.017	T
MetaRNN	Benign	0.24	T
MetaSVM	Benign	-0.64	T
MutationAssessor	Benign	1.8	L
MutationTaster	Benign	1.0	D
PrimateAI	Uncertain	0.59	T
PROVEAN	Benign	-1.6	N
REVEL	Benign	0.20
Sift	Benign	0.17	T
Sift4G	Benign	0.37	T
Polyphen		0.011	B
Vest4		0.19
MutPred		0.52		Loss of phosphorylation at S196 (P = 0.0203);
MVP		0.73
MPC		1.0
ClinPred		0.18	T
GERP RS		5.7
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.11
gMVP		0.47

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: rs765835212; hg19: chr20-32439985;