chr2-218661308-G-T

Position:

chr2-218661308-G-T

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1_StrongPM2PP3_StrongPP5_Very_Strong

The NM_001079866.2(BCS1L):c.320+1G>T variant causes a splice donor change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.0000316 in 1,614,096 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Likely pathogenic (★★).

Frequency

Genomes: 𝑓 0.000033 ( 0 hom., cov: 32)

Exomes 𝑓: 0.000031 ( 0 hom. )

Consequence

BCS1L
NM_001079866.2 splice_donor

Scores

Splicing: ADA: 1.000

Clinical Significance

Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:9

Conservation

PhyloP100: 9.98

Variant links:

Genes affected

BCS1L (HGNC:1020): (BCS1 homolog, ubiquinol-cytochrome c reductase complex chaperone) This gene encodes a homolog of the S. cerevisiae bcs1 protein which is involved in the assembly of complex III of the mitochondrial respiratory chain. The encoded protein does not contain a mitochondrial targeting sequence but experimental studies confirm that it is imported into mitochondria. Mutations in this gene are associated with mitochondrial complex III deficiency and the GRACILE syndrome. Several alternatively spliced transcripts encoding two different isoforms have been described. [provided by RefSeq, Jan 2016]

BCS1L links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Pathogenic. Variant got 18 ACMG points.

PVS1

Splicing variant, NOT destroyed by nmd, known LOF gene, truncates exone, which is 0.2920635 fraction of the gene. Cryptic splice site detected, with MaxEntScore 5.9, offset of 5, new splice context is: aagGTgggg. Cryptic site results in frameshift change. If cryptic site found is not functional and variant results in exon loss, it results in inframe change.

PM2

Very rare variant in population databases, with high coverage;

PP3

Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF, max_spliceai. No scorers claiming Uncertain. No scorers claiming Benign.

PP5

Variant 2-218661308-G-T is Pathogenic according to our data. Variant chr2-218661308-G-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 56412.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr2-218661308-G-T is described in Lovd as [Likely_pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
BCS1L	NM_001079866.2 linkuse as main transcript	c.320+1G>T		splice_donor_variant		ENST00000359273.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
BCS1L	ENST00000359273.8 linkuse as main transcript	c.320+1G>T		splice_donor_variant		1	NM_001079866.2	P1

Frequencies

GnomAD3 genomes

AF:

0.0000328

AC:

AN:

152218

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000241

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:

0.0000588

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.0000120

AC:

AN:

250504

Hom.:

AF XY:

0.00000736

AC XY:

AN XY:

135810

show subpopulations

Gnomad AFR exome

AF:

0.0000642

Gnomad AMR exome

AF:

0.00

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:

0.0000176

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.0000315

AC:

AN:

1461878

Hom.:

Cov.:

AF XY:

0.0000316

AC XY:

AN XY:

727238

show subpopulations

Gnomad4 AFR exome

AF:

0.0000299

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:

0.0000396

Gnomad4 OTH exome

AF:

0.0000166

GnomAD4 genome

AF:

0.0000328

AC:

AN:

152218

Hom.:

Cov.:

AF XY:

0.0000134

AC XY:

AN XY:

74370

show subpopulations

Gnomad4 AFR

AF:

0.0000241

Gnomad4 AMR

AF:

0.00

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.0000588

Gnomad4 OTH

AF:

0.00

Alfa

AF:

0.0000278

Hom.:

Bravo

AF:

0.0000264

ExAC

AF:

0.0000330

AC:

EpiCase

AF:

0.0000545

EpiControl

AF:

0.00

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:9

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

GRACILE syndrome

Pathogenic:3

Likely pathogenic, criteria provided, single submitter	literature only	Counsyl	Sep 12, 2014	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	May 23, 2022	Variant summary: BCS1L c.320+1G>T alters a conserved nucleotide located in a canonical splice-site and is predicted to affect mRNA splicing resulting in a significantly altered protein due to either exon skipping, shortening, or inclusion of intronic material. Several computational tools predict a significant impact on normal splicing: Four predict the variant abolishes the canonical 5' splicing donor site. However, these predictions have yet to be confirmed by functional studies. The variant allele was found at a frequency of 1.2e-05 in 250504 control chromosomes. c.320+1G>T has been reported in the literature in individuals affected with GRACILE Syndrome (example, Visapaa_2002) and Bjornstad Syndrome (example, Hinson_2007). To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. Three clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation. Based on the evidence outlined above, the variant was classified as likely pathogenic. -
Likely pathogenic, no assertion criteria provided	literature only	Juha Muilu Group; Institute for Molecular Medicine Finland (FIMM)	-	- -

not provided

Pathogenic:3

Likely pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Oct 17, 2019	Canonical splice site variant in a gene for which loss-of-function is a known mechanism of disease; Not observed at a significant frequency in large population cohorts (Lek et al., 2016); This variant is associated with the following publications: (PMID: 25525159, 12215968, 17314340, 25895478) -
Pathogenic, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	May 05, 2023	- -
Pathogenic, criteria provided, single submitter	clinical testing	Invitae	Jan 17, 2024	This sequence change affects a donor splice site in intron 3 of the BCS1L gene. It is expected to disrupt RNA splicing. Variants that disrupt the donor or acceptor splice site typically lead to a loss of protein function (PMID: 16199547), and loss-of-function variants in BCS1L are known to be pathogenic (PMID: 12215968, 17314340, 19162478, 19508421, 22277166, 25895478). This variant is present in population databases (rs386833856, gnomAD 0.007%). Disruption of this splice site has been observed in individuals with GRACILE (growth retardation, aminoaciduria, cholestasis, iron overload, lactacidosis, and early death) syndrome and Bj√∂rnstad syndrome (PMID: 12215968, 17314340). This variant is also known as 321G>T and IVS2+1G>T. ClinVar contains an entry for this variant (Variation ID: 56412). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. For these reasons, this variant has been classified as Pathogenic. -

Pili torti-deafness syndrome

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Baylor Genetics

Dec 04, 2023

- -

Mitochondrial complex III deficiency nuclear type 1

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Apr 24, 2024

- -

Inborn genetic diseases

Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Nov 05, 2020

The c.320+1G>T intronic variant results from a G to T substitution one nucleotide after exon 3 (coding exon 1) of the BCS1L gene. Alterations that disrupt the canonical splice site are expected to result in aberrant splicing. In silico splice site analysis predicts that this alteration will weaken the native splice donor site and will result in the creation or strengthening of a novel splice donor site. The resulting transcript is predicted to disrupt the methionine residue at the initiation codon (ATG) or cause a shift in the mRNA reading frame; however, direct evidence is unavailable. This alteration may escape nonsense-mediated mRNAdecay and/or be prone to rescue by reinitation (Rivas, 2015; Lindeboom, 2016; Rhee, 2017), and would impact the first 120 amino acids of the protein. The exact functional effect of this alteration is unknown; however, the impacted region is critical for protein function and a significant portion of the protein is affected (Ambry internal data). Based on data from the Genome Aggregation Database (gnomAD) database, the BCS1L c.320+1G>T alteration was observed in 0.0012% (3/250504) of total alleles studied. This alteration has been reported in an individual with GRACILE syndrome (Visapää, 2002) and in trans with another alteration in BCSL1 in an individual with Björnstad syndrome (Hinson, 2007). This nucleotide position is highly conserved in available vertebrate species. Based on the available evidence, this alteration is classified as likely pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_addAF

Pathogenic

0.46

BayesDel_noAF

Uncertain

0.060

CADD

Pathogenic

DANN

Uncertain

0.99

Eigen

Pathogenic

1.1

Eigen_PC

Pathogenic

0.95

FATHMM_MKL

Uncertain

0.96

MutationTaster

Benign

1.0

D;D;D;D;D;D;D

GERP RS

4.5

Splicing

Name

Calibrated prediction

Score

Prediction

dbscSNV1_ADA

Pathogenic

1.0

dbscSNV1_RF

Pathogenic

0.94

SpliceAI score (max)

0.95

Details are displayed if max score is > 0.2

DS_DG_spliceai

0.50

Position offset: 4

DS_DL_spliceai

0.95

Position offset: -1

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