rs104893692

Positions:

• chr3-15645322-A-C

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 2P and 1B. PM2 BP4

The NM_001370658.1(BTD):​c.1406A>C​(p.Asn469Thr) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000192 in 1,461,892 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 14/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.000019 (0 hom.)
• Consequence: BTD NM_001370658.1 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2 U:4
• Conservation: PhyloP100: 3.22

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 Uncertain_significance. Variant got 1 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.38277918).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
BTD	NM_001370658.1	c.1406A>C	p.Asn469Thr	missense_variant	4/4	ENST00000643237.3	NP_001357587.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
BTD	ENST00000643237.3	c.1406A>C	p.Asn469Thr	missense_variant	4/4		NM_001370658.1	ENSP00000495254	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.0000159 AC: 4 AN: 251444 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 135896

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000289

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.000163

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 AF: 0.0000192 AC: 28 AN: 1461892 Hom.: 0 Cov.: 32 AF XY: 0.0000165 AC XY: 12 AN XY: 727248

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.0000224

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.000655

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome Cov.: 32

ExAC AF: 0.0000330 AC: 4

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2 Uncertain:4

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Biotinidase deficiency Pathogenic:2 Uncertain:2

Pathogenic, no assertion criteria provided	literature only	OMIM	Jun 01, 1998	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Jan 30, 2024	This sequence change replaces asparagine, which is neutral and polar, with threonine, which is neutral and polar, at codon 489 of the BTD protein (p.Asn489Thr). This variant is present in population databases (rs104893692, gnomAD 0.02%). This missense change has been observed in individual(s) with biotinidase deficiency (PMID: 9705240; Invitae). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. ClinVar contains an entry for this variant (Variation ID: 1903). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt BTD protein function with a positive predictive value of 80%. This variant disrupts the p.Asn489 amino acid residue in BTD. Other variant(s) that disrupt this residue have been observed in individuals with BTD-related conditions (PMID: 28498829), which suggests that this may be a clinically significant amino acid residue. In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. -
Uncertain significance, criteria provided, single submitter	clinical testing	Illumina Laboratory Services, Illumina	Apr 27, 2017	The BTD c.1466A>C (Asn489Thr) variant has been reported in three studies and was found in a homozygous state in one individual with 10.8% of the mean normal biotinyl hydrolase activity (Pomponio et al. 1998). This individual was also homozygous for an additional polymorphism, and each of the individual's parents was shown to be a heterozygous carrier of both variants. Control data are unavailable for this variant, which is reported at a frequency of 0.00046 in the East Asian population of the Exome Aggregation Consortium. The p.Asn489Thr variant is present in a well-conserved residue and is predicted to abolish a putative N-linked glycosylation site (Pomponio et al. 1998; Pindolia et al. 2010). Based on the evidence, the p.Asn489Thr variant is classified as a variant of unknown significance but suspicious for pathogenicity for biotinidase deficiency. This variant was observed by ICSL as part of a predisposition screen in an ostensibly healthy population. -
Uncertain significance, criteria provided, single submitter	clinical testing	Counsyl	Jan 05, 2018	- -

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

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

Apr 28, 2023

Variant summary: BTD c.1406A>C (p.Asn469Thr) results in a non-conservative amino acid change in the encoded protein sequence. Three of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 1.6e-05 in 251444 control chromosomes. c.1406A>C has been reported in the literature as a homozygous genotype in at-least one individual affected with Biotinidase Deficiency (example, Pomponio_1998). These data indicate that the variant may be associated with disease. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. The following publications have been ascertained in the context of this evaluation (PMID: 28498829, 20556795, 9705240). Four clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation (VUS, n=3; LP, n=1). Based on the evidence outlined above, the variant was classified as VUS-possibly pathogenic. -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

GeneDx

Jan 26, 2022

In silico analysis supports that this missense variant does not alter protein structure/function; This variant is associated with the following publications: (PMID: 9705240, 20556795) -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.24
BayesDel_addAF	Benign	-0.17	T
BayesDel_noAF	Benign	-0.19
CADD	Benign	21
DANN	Benign	0.82
DEOGEN2	Benign	0.29	.;.;T;.;.;.;.
Eigen	Benign	-0.029
Eigen_PC	Benign	0.13
FATHMM_MKL	Uncertain	0.84	D
LIST_S2	Benign	0.81	.;T;T;.;.;T;T
M_CAP	Benign	0.075	D
MetaRNN	Benign	0.38	T;T;T;T;T;T;T
MetaSVM	Uncertain	0.29	D
MutationAssessor	Benign	0.83	.;.;L;.;.;.;.
MutationTaster	Benign	1.0	A;A;A;A
PrimateAI	Uncertain	0.50	T
PROVEAN	Benign	-0.11	.;N;.;.;.;N;N
REVEL	Uncertain	0.36
Sift	Benign	1.0	.;T;.;.;.;T;T
Sift4G	Benign	1.0	.;T;.;.;.;T;T
Polyphen		0.71	.;.;P;.;.;.;.
Vest4		0.67, 0.76, 0.62
MutPred		0.83		.;.;Gain of helix (P = 0.0696);.;.;.;.;
MVP		0.98
MPC		0.16
ClinPred		0.12	T
GERP RS		5.6
Varity_R		0.067
gMVP		0.72

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: rs104893692; hg19: chr3-15686829;