rs397514335

Positions:

• chr3-15645127-G-A
• chr3-15645127-G-C

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PM1 PM2 PM5 PP3_Strong PP5_Very_Strong

The NM_001370658.1(BTD):​c.1211G>A​(p.Cys404Tyr) variant causes a missense change involving the alteration of a 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 Likely pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. C404S) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: BTD NM_001370658.1 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 9.92

Genes affected

BTD (HGNC:1122): (biotinidase) The protein encoded by this gene functions to recycle protein-bound biotin by cleaving biocytin (biotin-epsilon-lysine), a normal product of carboxylase degradation, resulting in regeneration of free biotin. The encoded protein has also been shown to have biotinyl transferase activity. Mutations in this gene are associated with biotinidase deficiency. Multiple transcript variants encoding different isoforms have been described. [provided by RefSeq, Aug 2013]

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PM1: In a hotspot region, there are 2 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 4 uncertain in NM_001370658.1
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr3-15645127-G-C is described in ClinVar as [Pathogenic]. Clinvar id is 1675907.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.995
• PP5: Variant 3-15645127-G-A is Pathogenic according to our data. Variant chr3-15645127-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 25075.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr3-15645127-G-A is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
BTD	NM_001370658.1	c.1211G>A	p.Cys404Tyr	missense_variant	4/4	ENST00000643237.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
BTD	ENST00000643237.3	c.1211G>A	p.Cys404Tyr	missense_variant	4/4		NM_001370658.1	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251376 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 135852

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000289

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Biotinidase deficiency Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	Invitae	Aug 07, 2021	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 disruptive, but these predictions have not been confirmed by published functional studies and their clinical significance is uncertain. For these reasons, this variant has been classified as Pathogenic. This variant disrupts the p.Cys424 amino acid residue in BTD. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 15776412, 29359854). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. This variant has been observed to be homozygous in an individual affected with biotinidase deficiency (PMID: 15776412). ClinVar contains an entry for this variant (Variation ID: 25075). This variant is not present in population databases (ExAC no frequency). This sequence change replaces cysteine with tyrosine at codon 424 of the BTD protein (p.Cys424Tyr). The cysteine residue is highly conserved and there is a large physicochemical difference between cysteine and tyrosine. -
Likely pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Jan 06, 2023	Variant summary: BTD c.1211G>A (p.Cys404Tyr) results in a non-conservative amino acid change in the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 4e-06 in 251376 control chromosomes (gnomAD). c.1211G>A has been reported in the literature in at least one homozygous individual affected with profound Biotinidase Deficiency (Wolf_2005). These data indicate that the variant may be associated with disease. Serum biotinidase activity was completely absent (0% of control) in this homozygous individual (Wolf_2005). Two ClinVar submitters have assessed the variant since 2014: one classified the variant as likely pathogenic, and one as pathogenic. Based on the evidence outlined above, the variant was classified as likely pathogenic. -

not provided Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Dec 07, 2015

The C424Y variant has been reported previously in a patient with profound biotinidase deficiency who was homozygous for the C424Y variant (Wolf et al. 2005). The C424Y variant was not observed in approximately 6500 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project, indicating it is not a common benign variant in these populations. C424Y is a non-conservative amino acid substitution, which is likely to impact secondary protein structure as these residues differ in polarity, charge, size and/or other properties. This substitution occurs at a position that is conserved across species, and in silico analysis predicts this variant is probably damaging to the protein structure/function. Position 424 is reported to be crucial for ester formation and binding of the biotinyl-moiety in the active site of the biotinidase enzyme (Wolf et al., 2005). A missense variant at the same residue (C424S) and in nearby residues (C418S, C423R, C423S) have also been reported in the Human Gene Mutation Database in association with biotinidase deficiency (Stenson et al., 2014). Therefore, we interpret the C424Y variant to be likely pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.97
BayesDel_addAF	Pathogenic	0.49	D
BayesDel_noAF	Pathogenic	0.55
CADD	Uncertain	25
DANN	Uncertain	0.99
Eigen	Pathogenic	0.86
Eigen_PC	Pathogenic	0.77
FATHMM_MKL	Pathogenic	0.99	D
M_CAP	Pathogenic	0.38	D
MetaRNN	Pathogenic	1.0	D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Uncertain	0.73	T
Polyphen		1.0	.;.;D;.;.;.;.
Vest4		0.99, 0.99, 1.0
MutPred		0.95		.;.;Gain of helix (P = 0.0128);.;.;.;.;
MVP		1.0
MPC		0.54
ClinPred		1.0	D
GERP RS		5.6
Varity_R		0.94
gMVP		0.99

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: rs397514335; hg19: chr3-15686634;