NM_000100.4:c.202C>G

Variant names:

• chr21-43774297-G-C
• rs74315442
• NM_000100.4:c.202C>G

Variant summary

Our verdict is Uncertain significance. The variant received 2 ACMG points: 2P and 0B. PM2

The NM_000100.4(CSTB):​c.202C>G​(p.Arg68Gly) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000274 in 1,461,846 control chromosomes in the GnomAD database, with no homozygous occurrence. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R68P) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000027 (0 hom.)
• Consequence: CSTB NM_000100.4 missense
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 0.935
• Publications: 0 publications found

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 Gene-Disease associations (from GenCC):

• Unverricht-Lundborg syndrome

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: ClinGen, G2P, Orphanet, Labcorp Genetics (formerly Invitae)
• keratolytic winter erythema

  Inheritance: AD Classification: MODERATE Submitted by: PanelApp Australia
• genetic developmental and epileptic encephalopathy

  Inheritance: AR Classification: MODERATE Submitted by: ClinGen
• autosomal recessive hypohidrotic ectodermal dysplasia

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Uncertain_significance. The variant received 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000100.4. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	CSTB	NM_000100.4	MANE Select	c.202C>G	p.Arg68Gly	missense	Exon 3 of 3	NP_000091.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	CSTB	ENST00000291568.7	TSL:1 MANE Select	c.202C>G	p.Arg68Gly	missense	Exon 3 of 3	ENSP00000291568.6
	CSTB	ENST00000639959.1	TSL:5	c.67C>G	p.Arg23Gly	missense	Exon 2 of 2	ENSP00000492123.1
	CSTB	ENST00000675996.1		n.627C>G		non_coding_transcript_exon	Exon 3 of 3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.00000274 AC: 4 AN: 1461846 Hom.: 0 Cov.: 31 AF XY: 0.00000275 AC XY: 2 AN XY: 727222

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.0000299 AC: 1 AN: 33480

American (AMR) AF: 0.00 AC: 0 AN: 44724

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39700

South Asian (SAS) AF: 0.0000116 AC: 1 AN: 86258

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53382

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 0.00000180 AC: 2 AN: 1112004

Other (OTH) AF: 0.00 AC: 0 AN: 60394

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.000173310), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 33

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.51
BayesDel_addAF	Benign	-0.14	T
BayesDel_noAF	Benign	-0.43
CADD	Benign	18
DANN	Benign	0.95
DEOGEN2	Benign	0.42	T
Eigen	Benign	-0.62
Eigen_PC	Benign	-0.64
FATHMM_MKL	Benign	0.60	D
LIST_S2	Benign	0.79	T
M_CAP	Benign	0.0064	T
MetaRNN	Uncertain	0.61	D
MetaSVM	Benign	-1.0	T
PhyloP100		0.94
PrimateAI	Uncertain	0.58	T
PROVEAN	Pathogenic	-5.1	D
REVEL	Benign	0.11
Sift	Benign	0.039	D
Sift4G	Uncertain	0.032	D
Polyphen		0.039	B
Vest4		0.72
MutPred		0.63		Gain of catalytic residue at V69 (P = 0.0227)
MVP		0.14
MPC		0.20
ClinPred		0.93	D
GERP RS		-0.43
Varity_R		0.85
gMVP		0.79
Mutation Taster		=81/19	polymorphism

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

Other links and lift over

dbSNP: rs74315442; hg19: chr21-45194178;