chr1-100206459-A-C

Position:

• chr1-100206459-A-C

Variant summary

Our verdict is Pathogenic. Variant got 11 ACMG points: 11P and 0B. PM1 PM2 PM5 PP3_Strong PP5

The NM_001918.5(DBT):​c.1195T>G​(p.Ser399Ala) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.0000137 in 1,460,812 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. S399C) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.000014 (0 hom.)
• Consequence: DBT NM_001918.5 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:1
• Conservation: PhyloP100: 8.76

Genes affected

DBT (HGNC:2698): (dihydrolipoamide branched chain transacylase E2) The branched-chain alpha-keto acid dehydrogenase complex (BCKD) is an inner-mitochondrial enzyme complex involved in the breakdown of the branched-chain amino acids isoleucine, leucine, and valine. The BCKD complex is thought to be composed of a core of 24 transacylase (E2) subunits, and associated decarboxylase (E1), dehydrogenase (E3), and regulatory subunits. This gene encodes the transacylase (E2) subunit. Mutations in this gene result in maple syrup urine disease, type 2. Alternatively spliced transcript variants have been described, but their biological validity has not been determined. [provided by RefSeq, Jul 2008]

DBT (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 11 ACMG points.

• PM1: In a hotspot region, there are 4 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 6 uncertain in NM_001918.5
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr1-100206458-G-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 1333259.Status of the report is criteria_provided_single_submitter, 1 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.966
• PP5: Variant 1-100206459-A-C is Pathogenic according to our data. Variant chr1-100206459-A-C is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 551600.We mark this variant Likely_pathogenic, oryginal submissions are: {Uncertain_significance=1, Pathogenic=1}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
DBT	NM_001918.5	c.1195T>G	p.Ser399Ala	missense_variant	9/11	ENST00000370132.8	NP_001909.4

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
DBT	ENST00000370132.8	c.1195T>G	p.Ser399Ala	missense_variant	9/11	1	NM_001918.5	ENSP00000359151.3
DBT	ENST00000681617.1	c.1321T>G	p.Ser441Ala	missense_variant	10/12			ENSP00000505544.1
DBT	ENST00000681780.1	c.652T>G	p.Ser218Ala	missense_variant	10/12			ENSP00000505780.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.0000137 AC: 20 AN: 1460812 Hom.: 0 Cov.: 32 AF XY: 0.0000165 AC XY: 12 AN XY: 726800

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000144

Gnomad4 OTH exome AF: 0.0000663

GnomAD4 genome Cov.: 32

Alfa AF: 0.0000936 Hom.: 0

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Maple syrup urine disease Pathogenic:1 Uncertain:1

Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Oct 30, 2023	This sequence change replaces serine, which is neutral and polar, with alanine, which is neutral and non-polar, at codon 399 of the DBT protein (p.Ser399Ala). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with maple syrup urine disease (PMID: 27243974). 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: 551600). 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 DBT protein function with a positive predictive value of 95%. This variant disrupts the p.Ser399 amino acid residue in DBT. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 30228974). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. For these reasons, this variant has been classified as Pathogenic. -
Uncertain significance, criteria provided, single submitter	clinical testing	Counsyl	Apr 24, 2017	- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.83
BayesDel_addAF	Pathogenic	0.24	D
BayesDel_noAF	Uncertain	0.11
CADD	Pathogenic	27
DANN	Uncertain	1.0
Eigen	Pathogenic	1.0
Eigen_PC	Pathogenic	0.94
FATHMM_MKL	Pathogenic	0.99	D
M_CAP	Uncertain	0.16	D
MetaRNN	Pathogenic	0.97	D
MetaSVM	Uncertain	0.42	D
PrimateAI	Uncertain	0.71	T
PROVEAN	Uncertain	-2.9	D
REVEL	Pathogenic	0.71
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0	D
Vest4		0.88
MutPred		0.88		Loss of disorder (P = 0.1042);
MVP		0.91
MPC		0.96
ClinPred		0.99	D
GERP RS		5.5
gMVP		0.95

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: rs1553229654; hg19: chr1-100672015;