21-43072142-G-T

Variant names:

• chr21-43072142-G-T
• rs201827340
• NM_000071.3:c.52C>A

Variant summary

Our verdict is Likely benign. The variant received -3 ACMG points: 1P and 4B. PP2 BP4_Strong

The NM_000071.3(CBS):​c.52C>A​(p.Arg18Ser) variant causes a missense change involving the alteration of a non-conserved nucleotide. In-silico tool predicts a benign outcome for this variant. 13/22 in silico tools predict a benign outcome for this variant. 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. R18C) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 0)
• Consequence: CBS NM_000071.3 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 1.03
• Publications: 9 publications found

Genes affected

CBS (HGNC:1550): (cystathionine beta-synthase) The protein encoded by this gene acts as a homotetramer to catalyze the conversion of homocysteine to cystathionine, the first step in the transsulfuration pathway. The encoded protein is allosterically activated by adenosyl-methionine and uses pyridoxal phosphate as a cofactor. Defects in this gene can cause cystathionine beta-synthase deficiency (CBSD), which can lead to homocystinuria. This gene is a major contributor to cellular hydrogen sulfide production. Multiple alternatively spliced transcript variants have been found for this gene. [provided by RefSeq, Feb 2016]

CBS Gene-Disease associations (from GenCC):

• classic homocystinuria

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: G2P, Orphanet, Labcorp Genetics (formerly Invitae), Myriad Women’s Health, PanelApp Australia, ClinGen, Genomics England PanelApp

ACMG classification

Our verdict: Likely_benign. The variant received -3 ACMG points.

• PP2: Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 107 curated pathogenic missense variants (we use a threshold of 10). The gene has 4 curated benign missense variants. Gene score misZ: 0.8318 (below the threshold of 3.09). Trascript score misZ: NaN (below the threshold of 3.09). GenCC associations: The gene is linked to classic homocystinuria.
• BP4: Computational evidence support a benign effect (MetaRNN=0.052993476).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
CBS	NM_000071.3	c.52C>A	p.Arg18Ser	missense_variant	Exon 3 of 17	ENST00000398165.8	NP_000062.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
CBS	ENST00000398165.8	c.52C>A	p.Arg18Ser	missense_variant	Exon 3 of 17	1	NM_000071.3	ENSP00000381231.4

Frequencies

GnomAD3 genomes Cov.: 0

GnomAD4 exome Cov.: 0

GnomAD4 genome Cov.: 0

TwinsUK AF: 0.000270 AC: 1

ALSPAC AF: 0.00 AC: 0

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

HYPERHOMOCYSTEINEMIA, THROMBOTIC, CBS-RELATED Uncertain:1

Aug 28, 2021

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces arginine with serine at codon 18 of the CBS protein (p.Arg18Ser). The arginine residue is weakly conserved and there is a moderate physicochemical difference between arginine and serine. This variant is not present in population databases (ExAC no frequency). This variant has not been reported in the literature in individuals affected with CBS-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. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site. 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	0.10
BayesDel_addAF	Uncertain	0.047	T
BayesDel_noAF	Benign	-0.17
CADD	Benign	7.4
DANN	Benign	0.63
DEOGEN2	Benign	0.33	T;T;T;T;.
Eigen	Benign	-1.0
Eigen_PC	Benign	-0.97
FATHMM_MKL	Benign	0.22	N
LIST_S2	Benign	0.0	.;.;.;T;T
M_CAP	Uncertain	0.13	D
MetaRNN	Benign	0.053	T;T;T;T;T
MetaSVM	Uncertain	0.29	D
MutationAssessor	Benign	0.34	N;N;N;N;.
PhyloP100		1.0
PrimateAI	Benign	0.29	T
PROVEAN	Benign	0.27	N;N;N;N;N
REVEL	Uncertain	0.31
Sift	Benign	0.75	T;T;T;T;T
Sift4G	Benign	0.75	T;T;T;T;T
Vest4		0.17
ClinPred		0.027	T
GERP RS		3.0
Varity_R		0.20
gMVP		0.26
Mutation Taster		=99/1	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: rs201827340; hg19: chr21-44492252; COSMIC: COSV61446987; COSMIC: COSV61446987;