21-43065645-C-G

Variant names:

• chr21-43065645-C-G
• NM_000071.3:c.502G>C

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM1 PM5 PP3_Moderate

The NM_000071.3(CBS):​c.502G>C​(p.Val168Leu) variant causes a missense change. In-silico tool predicts a pathogenic 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. V168A) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 0)
• Consequence: CBS NM_000071.3 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 6.78

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]

ACMG classification

Verdict is Likely_pathogenic. Variant got 6 ACMG points.

• PM1: In a strand (size 6) in uniprot entity CBS_HUMAN there are 4 pathogenic changes around while only 0 benign (100%) in NM_000071.3
• PM5: Other missense variant is known to change same aminoacid residue: Variant chrnull-null-null-null is described in UniProt as null.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.925

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
CBS	NM_000071.3	c.502G>C	p.Val168Leu	missense_variant	Exon 6 of 17	ENST00000398165.8	NP_000062.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
CBS	ENST00000398165.8	c.502G>C	p.Val168Leu	missense_variant	Exon 6 of 17	1	NM_000071.3	ENSP00000381231.4

Frequencies

GnomAD3 genomes Cov.: 0

GnomAD4 exome Cov.: 0

GnomAD4 genome Cov.: 0

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

not specified Uncertain:1

May 21, 2024

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: CBS c.502G>C (p.Val168Leu) results in a conservative amino acid change located in the Tryptophan synthase beta chain-like, PALP domain (IPR001926) of the encoded protein sequence. Four of five in-silico tools predict a damaging effect of the variant on protein function. The variant was absent in 186900 control chromosomes. The available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. To our knowledge, no occurrence of c.502G>C in individuals affected with Homocystinuria and no experimental evidence demonstrating its impact on protein function have been reported. No submitters have cited clinical-significance assessments for this variant to ClinVar. Based on the evidence outlined above, the variant was classified as uncertain significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.91
BayesDel_addAF	Pathogenic	0.50	D
BayesDel_noAF	Pathogenic	0.48
CADD	Uncertain	26
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.97	D;D;D;D;.
Eigen	Pathogenic	0.69
Eigen_PC	Uncertain	0.62
FATHMM_MKL	Uncertain	0.94	D
LIST_S2	Pathogenic	0.99	.;.;.;D;D
M_CAP	Pathogenic	0.51	D
MetaRNN	Pathogenic	0.92	D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.3	M;M;M;M;.
PrimateAI	Uncertain	0.74	T
PROVEAN	Uncertain	-2.5	D;D;D;D;D
REVEL	Pathogenic	0.91
Sift	Uncertain	0.010	D;D;D;D;D
Sift4G	Uncertain	0.016	D;D;D;D;D
Polyphen		0.84	P;P;P;P;.
Vest4		0.90
MutPred		0.75		Loss of catalytic residue at V168 (P = 0.0688);Loss of catalytic residue at V168 (P = 0.0688);Loss of catalytic residue at V168 (P = 0.0688);Loss of catalytic residue at V168 (P = 0.0688);Loss of catalytic residue at V168 (P = 0.0688);
MVP		0.95
MPC		1.0
ClinPred		0.98	D
GERP RS		4.6
Varity_R		0.96
gMVP		0.85

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

No publications associated with this variant yet.

Other links and lift over

hg19: chr21-44485755;