20-23633981-G-A

Variant names:

• chr20-23633981-G-A
• NM_000099.4:c.376C>T

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 2P and 0B. PM2

The NM_000099.4(CST3):​c.376C>T​(p.Gln126*) variant causes a stop gained 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 Conflicting classifications of pathogenicity (no stars).

• Frequency: Genomes: not found (cov: 33)
• Consequence: CST3 NM_000099.4 stop_gained
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:1
• Conservation: PhyloP100: 0.924

Genes affected

CST3 (HGNC:2475): (cystatin C) 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 the kininogens. The type 2 cystatin proteins are a class of cysteine proteinase inhibitors found in a variety of human fluids and secretions, where they appear to provide protective functions. The cystatin locus on chromosome 20 contains the majority of the type 2 cystatin genes and pseudogenes. This gene is located in the cystatin locus and encodes the most abundant extracellular inhibitor of cysteine proteases, which is found in high concentrations in biological fluids and is expressed in virtually all organs of the body. A mutation in this gene has been associated with amyloid angiopathy. Expression of this protein in vascular wall smooth muscle cells is severely reduced in both atherosclerotic and aneurysmal aortic lesions, establishing its role in vascular disease. In addition, this protein has been shown to have an antimicrobial function, inhibiting the replication of herpes simplex virus. Alternative splicing results in multiple transcript variants encoding a single protein. [provided by RefSeq, Nov 2014]

ACMG classification

Verdict is Uncertain_significance. Variant got 2 ACMG points.

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

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
CST3	NM_000099.4	c.376C>T	p.Gln126*	stop_gained	Exon 3 of 3	ENST00000376925.8	NP_000090.1
CST3	NM_001288614.2	c.376C>T	p.Gln126*	stop_gained	Exon 3 of 4		NP_001275543.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
CST3	ENST00000376925.8	c.376C>T	p.Gln126*	stop_gained	Exon 3 of 3	1	NM_000099.4	ENSP00000366124.3
CST3	ENST00000398411.5	c.376C>T	p.Gln126*	stop_gained	Exon 3 of 4	1		ENSP00000381448.1
CST3	ENST00000398409.1	c.376C>T	p.Gln126*	stop_gained	Exon 4 of 4	3		ENSP00000381446.1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 33

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Hereditary cerebral amyloid angiopathy, Icelandic type Pathogenic:1

Mar 04, 2025

Institute of Human Genetics, University of Leipzig Medical Center

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Criteria applied: PVS1_MOD,PM2,PS4_SUP,PP4 -

not provided Uncertain:1

Oct 01, 2023

CeGaT Center for Human Genetics Tuebingen

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

CST3: PM2, PS4:Moderate -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.44	D
BayesDel_noAF	Pathogenic	0.39
CADD	Pathogenic	38
DANN	Uncertain	0.98
Eigen	Benign	0.12
Eigen_PC	Benign	-0.18
FATHMM_MKL	Benign	0.55	D
Vest4		0.88
GERP RS		-0.45
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.23		Details are displayed if max score is > 0.2
DS_AL_spliceai		0.23		Position offset: 18

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: chr20-23614618; COSMIC: COSV100976881; COSMIC: COSV100976881;