6-80273153-C-T

Variant names:

Variant summary

Our verdict is Pathogenic. The variant received 18 ACMG points: 18P and 0B. PVS1PM2PP5_Very_Strong

The NM_183050.4(BCKDHB):c.970C>T(p.Arg324*) variant causes a stop gained change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000026 in 1,613,042 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 Likely pathogenic (★★). Synonymous variant affecting the same amino acid position (i.e. R324R) has been classified as Likely benign. Variant results in nonsense mediated mRNA decay.

Frequency

Genomes: 𝑓 0.000013 ( 0 hom., cov: 33)

Exomes 𝑓: 0.000027 ( 0 hom. )

Consequence

BCKDHB
NM_183050.4 stop_gained

Scores

Clinical Significance

Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:13

Conservation

PhyloP100: 1.67

Publications

9 publications found

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 Gene-Disease associations (from GenCC):

maple syrup urine disease type 1B
Inheritance: AR Classification: DEFINITIVE Submitted by: ClinGen, G2P, Myriad Women’s Health
maple syrup urine disease
Inheritance: AR Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae)
classic maple syrup urine disease
Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
intermediate maple syrup urine disease
Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
intermittent maple syrup urine disease
Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
thiamine-responsive maple syrup urine disease
Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

BCKDHB links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Pathogenic. The variant received 18 ACMG points.

PVS1

Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.

PM2

Very rare variant in population databases, with high coverage;

PP5

Variant 6-80273153-C-T is Pathogenic according to our data. Variant chr6-80273153-C-T is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 96621.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
BCKDHB	NM_183050.4 link	c.970C>T	p.Arg324*	stop_gained	Exon 9 of 10	ENST00000320393.9	NP_898871.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein
BCKDHB	ENST00000320393.9 link	c.970C>T	p.Arg324*	stop_gained	Exon 9 of 10	1	NM_183050.4	ENSP00000318351.5
BCKDHB	ENST00000356489.9 link	c.970C>T	p.Arg324*	stop_gained	Exon 9 of 11	1		ENSP00000348880.5
BCKDHB	ENST00000468520.1 link	n.200C>T		non_coding_transcript_exon_variant	Exon 3 of 3	5

Frequencies

GnomAD3 genomes

AF:

0.0000132

AC:

AN:

152034

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

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:

0.0000294

Gnomad OTH

AF:

0.00

GnomAD2 exomes

AF:

0.0000598

AC:

AN:

250890

AF XY:

0.0000590

show subpopulations

Gnomad AFR exome

AF:

0.0000616

Gnomad AMR exome

AF:

0.000203

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.0000529

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.0000274

AC:

AN:

1461008

Hom.:

Cov.:

AF XY:

0.0000248

AC XY:

AN XY:

726822

show subpopulations

African (AFR)

AF:

0.0000598

AC:

AN:

33440

American (AMR)

AF:

0.000134

AC:

AN:

44672

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26096

East Asian (EAS)

AF:

0.0000504

AC:

AN:

39660

South Asian (SAS)

AF:

0.0000232

AC:

AN:

86246

European-Finnish (FIN)

AF:

0.00

AC:

AN:

53384

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5758

European-Non Finnish (NFE)

AF:

0.0000216

AC:

AN:

1111396

Other (OTH)

AF:

0.0000663

AC:

AN:

60356

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.434

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

GnomAD4 genome

AF:

0.0000132

AC:

AN:

152034

Hom.:

Cov.:

AF XY:

0.0000135

AC XY:

AN XY:

74262

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

41398

American (AMR)

AF:

0.00

AC:

AN:

15244

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3466

East Asian (EAS)

AF:

0.00

AC:

AN:

5190

South Asian (SAS)

AF:

0.00

AC:

AN:

4826

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10596

Middle Eastern (MID)

AF:

0.00

AC:

AN:

316

European-Non Finnish (NFE)

AF:

0.0000294

AC:

AN:

67998

Other (OTH)

AF:

0.00

AC:

AN:

2088

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.550

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Genome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

Alfa

AF:

0.0000224

Hom.:

Bravo

AF:

0.0000416

ExAC

AF:

0.0000741

AC:

EpiCase

AF:

0.00

EpiControl

AF:

0.000119

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:13

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

Maple syrup urine disease

Pathogenic:5

Sep 23, 2014

Counsyl

Significance:Likely pathogenic

Review Status:no assertion criteria provided

Collection Method:literature only

This submission and the accompanying classification are no longer maintained by the submitter. For more information on current observations and classification, please contact variantquestions@myriad.com. -

May 07, 2019

Baylor Genetics

Significance:Pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

This variant was determined to be pathogenic according to ACMG Guidelines, 2015 [PMID:25741868]. This variant has been previously reported as disease-causing [PMID 9375800, 26232051, 25525159] -

Feb 24, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance:Pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

This sequence change creates a premature translational stop signal (p.Arg324*) in the BCKDHB gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in BCKDHB are known to be pathogenic (PMID: 16786533, 22593002). This variant is present in population databases (rs398124603, gnomAD 0.02%). This premature translational stop signal has been observed in individual(s) with maple syrup urine disease (PMID: 20307994, 22593002, 24772966, 26232051). This variant is also known as p.Arg274*. ClinVar contains an entry for this variant (Variation ID: 96621). For these reasons, this variant has been classified as Pathogenic. -

Aug 27, 2016

Illumina Laboratory Services, Illumina

Significance:Likely pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

The BCKDHB c.970C>T (p.Arg324Ter) stop-gained variant is reported in five studies in a total of six individuals with maple syrup urine disease, including one who was homozygous for the variant and five, including a sibling pair, who were compound heterozygous (McConnell et al. 1997; Puckett et al. 2010; Bashyam et al. 2012; Narayanan et al. 2013; Couce et al. 2015). The p.Arg324Ter variant was absent from 100 controls and is reported at a frequency of 0.00044 in the Latino population of the Exome Aggregation Consortium. Functional studies in patient lymphoblasts carrying the p.Arg324Ter variant demonstrate that variant BCKD enzyme activity is <1% of that of the control enzyme activity. Western blotting experiments showed that the variant resulted in a truncated protein which was not detected in the mitochondria suggesting that the missing amino acids may be necessary for tetramer formation (McConnell et al. 1997; Nellis et al. 2003). Based on the evidence and the potential impact of stop-gained variants, the p.Arg324Ter variant is classified as pathogenic for maple syrup urine disease. This variant was observed by ICSL as part of a predisposition screen in an ostensibly healthy population. -

Nov 07, 2021

Genome-Nilou Lab

Significance:Likely pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

Maple syrup urine disease type 1B

Pathogenic:3

Sep 16, 2020

Natera, Inc.

Significance:Pathogenic

Review Status:no assertion criteria provided

Collection Method:clinical testing

- -

Sep 28, 2018

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

Significance:Pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Variant summary: BCKDHB c.970C>T (p.Arg324X) results in a premature termination codon, predicted to cause a truncation of the encoded protein or absence of the protein due to nonsense mediated decay, which are commonly known mechanisms for disease. The variant allele was found at a frequency of 6.1e-05 in 245644 control chromosomes (gnomAD). This frequency is not higher than expected for a pathogenic variant in BCKDHB causing Maple Syrup Urine Disease Type 1B (6.1e-05 vs 0.0015), allowing no conclusion about variant significance. c.970C>T has been reported in the literature in multiple individuals affected with Maple Syrup Urine Disease Type 1B (Bashyam_2012, Couce_2015, McConnell_1997, Narayanan_2013, Puckett_2010). These data indicate that the variant is very likely to be associated with disease. At least one publication reports experimental evidence evaluating an impact on protein function. The most pronounced variant effect results in <10% of normal activity (McConnell_1997). Three ClinVar submissions from clinical diagnostic laboratories (evaluation after 2014) cites the variant as likely pathogenic/pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic. -

Jan 30, 2024

Fulgent Genetics, Fulgent Genetics

Significance:Pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

not provided

Pathogenic:3

Diagnostic Laboratory, Department of Genetics, University Medical Center Groningen

Significance:Pathogenic

Review Status:no assertion criteria provided

Collection Method:clinical testing

- -

Apr 12, 2017

Eurofins Ntd Llc (ga)

Significance:Pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

Clinical Genetics, Academic Medical Center

Significance:Pathogenic

Review Status:no assertion criteria provided

Collection Method:clinical testing

- -

Maple syrup urine disease type 1A

Pathogenic:2

Mar 08, 2024

Baylor Genetics

Significance:Pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

Feb 23, 2024

3billion

Significance:Pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

The variant is observed at an extremely low frequency in the gnomAD v2.1.1 dataset (total allele frequency: 0.006%). Predicted Consequence/Location: Stop-gained (nonsense): predicted to result in a loss or disruption of normal protein function through nonsense-mediated decay (NMD) or protein truncation. Multiple pathogenic variants are reported downstream of the variant. The variant has been reported at least twice as pathogenic with clinical assertions and evidence for the classification (ClinVar ID: VCV000096621 /PMID: 9375800 /3billion dataset). Therefore, this variant is classified as Pathogenic according to the recommendation of ACMG/AMP guideline. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_addAF

Pathogenic

0.43

BayesDel_noAF

Pathogenic

0.62

CADD

Pathogenic

(source)

DANN

Uncertain

1.0

Eigen

Uncertain

0.60

Eigen_PC

Uncertain

0.44

FATHMM_MKL

Uncertain

0.93

PhyloP100

1.7

Vest4

0.94

GERP RS

3.9

Mutation Taster

=0/200

disease causing (ClinVar)

(source)

Splicing

Name

Calibrated prediction

Score

Prediction

Splicevardb

2.0

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

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over