6-80168906-G-C

Position:

chr6-80168906-G-C

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PM2PP3_Moderate

The NM_183050.4(BCKDHB):c.509G>C(p.Arg170Pro) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000434 in 1,613,930 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 12/21 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

Frequency

Genomes: 𝑓 0.0000066 ( 0 hom., cov: 32)

Exomes 𝑓: 0.0000041 ( 0 hom. )

Consequence

BCKDHB
NM_183050.4 missense

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2U:3

Conservation

PhyloP100: 9.49

Variant links:

Genes affected

BCKDHB (HGNC:987): (branched chain keto acid dehydrogenase E1 subunit beta) This gene encodes the E1 beta subunit of branched-chain keto acid dehydrogenase, which is a multienzyme complex associated with the inner membrane of mitochondria. This enzyme complex functions in the catabolism of branched-chain amino acids. Mutations in this gene have been associated with maple syrup urine disease (MSUD), type 1B, a disease characterized by a maple syrup odor to the urine in addition to mental and physical retardation and feeding problems. Alternative splicing at this locus results in multiple transcript variants. [provided by RefSeq, Jan 2016]

BCKDHB links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Uncertain_significance. Variant got 4 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

PP3

MetaRNN computational evidence supports a deleterious effect, 0.938

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
BCKDHB	NM_183050.4 linkuse as main transcript	c.509G>C	p.Arg170Pro	missense_variant	5/10	ENST00000320393.9	NP_898871.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
BCKDHB	ENST00000320393.9 linkuse as main transcript	c.509G>C	p.Arg170Pro	missense_variant	5/10	1	NM_183050.4	ENSP00000318351	P1	P21953-1
BCKDHB	ENST00000356489.9 linkuse as main transcript	c.509G>C	p.Arg170Pro	missense_variant	5/11	1		ENSP00000348880	P1	P21953-1
BCKDHB	ENST00000369760.8 linkuse as main transcript	c.509G>C	p.Arg170Pro	missense_variant	5/6	3		ENSP00000358775		P21953-2

Frequencies

GnomAD3 genomes

AF:

0.00000658

AC:

AN:

152076

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.0000655

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.00

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.0000199

AC:

AN:

251426

Hom.:

AF XY:

0.0000147

AC XY:

AN XY:

135888

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.000145

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

AF:

0.00000410

AC:

AN:

1461854

Hom.:

Cov.:

AF XY:

0.00000413

AC XY:

AN XY:

727232

show subpopulations

Gnomad4 AFR exome

AF:

0.00

Gnomad4 AMR exome

AF:

0.000134

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:

0.00

Gnomad4 OTH exome

AF:

0.00

GnomAD4 genome

AF:

0.00000658

AC:

AN:

152076

Hom.:

Cov.:

AF XY:

0.0000135

AC XY:

AN XY:

74288

show subpopulations

Gnomad4 AFR

AF:

0.00

Gnomad4 AMR

AF:

0.0000655

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.00

Gnomad4 OTH

AF:

0.00

Bravo

AF:

0.00000378

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2Uncertain:3

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

Maple syrup urine disease

Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Genome-Nilou Lab	Nov 07, 2021	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Aug 12, 2022	This sequence change replaces arginine, which is basic and polar, with proline, which is neutral and non-polar, at codon 170 of the BCKDHB protein (p.Arg170Pro). This variant is present in population databases (rs371518124, gnomAD 0.01%). This variant has not been reported in the literature in individuals affected with BCKDHB-related conditions. ClinVar contains an entry for this variant (Variation ID: 96592). Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C15"). This variant disrupts the p.Arg170 amino acid residue in BCKDHB. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 22326532; Invitae). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. 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. -

Inborn genetic diseases

Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Jan 13, 2022

The c.509G>C (p.R170P) alteration is located in exon 5 (coding exon 5) of the BCKDHB gene. This alteration results from a G to C substitution at nucleotide position 509, causing the arginine (R) at amino acid position 170 to be replaced by a proline (P). Based on data from gnomAD, the C allele has an overall frequency of <0.01% (5/251426) total alleles studied. The highest observed frequency was 0.01% (5/34592) of Latino alleles. This variant was identified as homozygous in an individual affected with Maple syrup urine disease (Clinvar database). In addition, multiple different variants at this position have been described in patients with Maple syrup urine disease including p.R170H, p.R170C, and p.R170G (Li, 2018; Abiri, 2019; Strauss, 2020; O'Reilly, 2021). Based on internal structural analysis, the p.R170P variant was determined to be more destabilizing than these previously reported variants (Ambry internal data). This amino acid position is highly conserved in available vertebrate species. This alteration is predicted to be deleterious by in silico analysis. Based on the available evidence, this alteration is classified as likely pathogenic. -

BCKDHB-related disorder

Pathogenic:1

Likely pathogenic, no assertion criteria provided

clinical testing

PreventionGenetics, part of Exact Sciences

May 03, 2024

The BCKDHB c.509G>C variant is predicted to result in the amino acid substitution p.Arg170Pro. To our knowledge, this variant has not been reported in the literature. However, alternate nucleotide substitutions affecting the same amino acid (p.Arg170Cys, p.Arg170His, and p.Arg170Gly) have been reported in the homozygous and compound heterozygous states in multiple individuals with maple syrup urine disease (see for example, Miryounesi et al. 2015. PubMed ID: 25381949; Table 3, OReilly et al. 2020. PubMed ID: 33300147; Table S1, Strauss et al. 2020. PubMed ID: 31980395). The p.Arg170 amino acid has been highly evolutionarily conserved (Alamut Visual v2.11). In silico analysis suggested that the p.Arg170 residue is in close proximity to the K+ binding site in the branched-chain alpha-ketoacid dehydrogenase (BCKD) enzyme complex, and that substitutions of this amino acid may cause unstable dimer assembly and an unstable K+ ion binding loop (Miryounesi et al. 2015. PubMed ID: 25381949). This variant is reported in 0.014% of alleles in individuals of Latino descent in gnomAD. This variant is interpreted as likely pathogenic. -

not provided

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Eurofins Ntd Llc (ga)

Oct 31, 2012

- -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Pathogenic

1.0

BayesDel_addAF

Pathogenic

0.33

BayesDel_noAF

Pathogenic

0.47

CADD

Pathogenic

DANN

Uncertain

1.0

DEOGEN2

Uncertain

0.76

.;D;D

Eigen

Pathogenic

0.82

Eigen_PC

Pathogenic

0.67

FATHMM_MKL

Pathogenic

0.99

LIST_S2

Pathogenic

0.99

D;.;D

M_CAP

Pathogenic

0.62

MetaRNN

Pathogenic

0.94

D;D;D

MetaSVM

Pathogenic

1.0

MutationAssessor

Pathogenic

4.5

H;H;H

MutationTaster

Benign

1.0

D;D;D;D

PrimateAI

Pathogenic

0.83

PROVEAN

Pathogenic

-6.9

D;D;D

REVEL

Pathogenic

0.87

Sift

Pathogenic

0.0

D;D;D

Sift4G

Uncertain

0.015

D;D;D

Polyphen

1.0

.;D;D

Vest4

0.96

MutPred

0.72

Gain of loop (P = 0.0079);Gain of loop (P = 0.0079);Gain of loop (P = 0.0079);

MVP

0.99

MPC

0.94

ClinPred

1.0

GERP RS

4.2

Varity_R

0.99

gMVP

0.98

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

Below is the list of publications found by LitVar. It may be empty.

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

LitVar

Other links and lift over