chr21-43774296-C-G

Position:

• chr21-43774296-C-G

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM1 PM2 PP3_Moderate

The NM_000100.4(CSTB):​c.203G>C​(p.Arg68Pro) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: not found (cov: 33)
• Consequence: CSTB NM_000100.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 1.96

Genes affected

CSTB (HGNC:2482): (cystatin B) The cystatin superfamily encompasses proteins that contain multiple cystatin-like sequences. Some of the members are active cysteine protease inhibitors, while others have lost or perhaps never acquired this inhibitory activity. There are three inhibitory families in the superfamily, including the type 1 cystatins (stefins), type 2 cystatins and kininogens. This gene encodes a stefin that functions as an intracellular thiol protease inhibitor. The protein is able to form a dimer stabilized by noncovalent forces, inhibiting papain and cathepsins l, h and b. The protein is thought to play a role in protecting against the proteases leaking from lysosomes. Evidence indicates that mutations in this gene are responsible for the primary defects in patients with progressive myoclonic epilepsy (EPM1). One type of mutation responsible for EPM1 is the expansion in the promoter region of this gene of a CCCCGCCCCGCG repeat from 2-3 copies to 30-78 copies. [provided by RefSeq, Jul 2016]

CSTB (HGNC:):

ACMG classification

Verdict is Likely_pathogenic. Variant got 6 ACMG points.

• PM1: In a chain Cystatin-B (size 97) in uniprot entity CYTB_HUMAN there are 6 pathogenic changes around while only 2 benign (75%) in NM_000100.4
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.878

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
CSTB	NM_000100.4	c.203G>C	p.Arg68Pro	missense_variant	3/3	ENST00000291568.7	NP_000091.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
CSTB	ENST00000291568.7	c.203G>C	p.Arg68Pro	missense_variant	3/3	1	NM_000100.4	ENSP00000291568.6

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Progressive myoclonic epilepsy Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Sep 01, 2021

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.93
BayesDel_addAF	Uncertain	0.073	D
BayesDel_noAF	Benign	-0.13
CADD	Benign	21
DANN	Uncertain	0.99
DEOGEN2	Uncertain	0.46	T
Eigen	Benign	0.052
Eigen_PC	Benign	-0.095
FATHMM_MKL	Benign	0.67	D
LIST_S2	Uncertain	0.90	D
M_CAP	Benign	0.022	T
MetaRNN	Pathogenic	0.88	D
MetaSVM	Benign	-1.0	T
PrimateAI	Uncertain	0.61	T
PROVEAN	Pathogenic	-5.3	D
REVEL	Benign	0.27
Sift	Uncertain	0.0030	D
Sift4G	Uncertain	0.0030	D
Polyphen		0.99	D
Vest4		0.78
MutPred		0.68		Loss of sheet (P = 0.0817);
MVP		0.18
MPC		0.69
ClinPred		0.98	D
GERP RS		3.6
Varity_R		0.99
gMVP		0.87

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: rs757707761; hg19: chr21-45194177;