2-237359205-C-T

Position:

• chr2-237359205-C-T

Variant summary

Our verdict is Pathogenic. Variant got 12 ACMG points: 12P and 0B. PVS1_Moderate PM2 PP5_Very_Strong

The NM_004369.4(COL6A3):​c.6354+1G>A variant causes a splice donor, intron change. The variant was absent in control chromosomes in GnomAD project. 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: not found (cov: 33)
• Consequence: COL6A3 NM_004369.4 splice_donor, intron
• Scores: Splicing: ADA: 0.9999
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:5 O:1
• Conservation: PhyloP100: 7.20

Genes affected

COL6A3 (HGNC:2213): (collagen type VI alpha 3 chain) This gene encodes the alpha-3 chain, one of the three alpha chains of type VI collagen, a beaded filament collagen found in most connective tissues. The alpha-3 chain of type VI collagen is much larger than the alpha-1 and -2 chains. This difference in size is largely due to an increase in the number of subdomains, similar to von Willebrand Factor type A domains, that are found in the amino terminal globular domain of all the alpha chains. These domains have been shown to bind extracellular matrix proteins, an interaction that explains the importance of this collagen in organizing matrix components. Mutations in the type VI collagen genes are associated with Bethlem myopathy, a rare autosomal dominant proximal myopathy with early childhood onset. Mutations in this gene are also a cause of Ullrich congenital muscular dystrophy, also referred to as Ullrich scleroatonic muscular dystrophy, an autosomal recessive congenital myopathy that is more severe than Bethlem myopathy. Multiple transcript variants have been identified, but the full-length nature of only some of these variants has been described. [provided by RefSeq, Jun 2009]

ACMG classification

Verdict is Pathogenic. Variant got 12 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.004615062 fraction of the gene. No cryptic splice site detected. Exon removal is inframe change.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 2-237359205-C-T is Pathogenic according to our data. Variant chr2-237359205-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 285748.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr2-237359205-C-T is described in Lovd as [Likely_pathogenic]. Variant chr2-237359205-C-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
COL6A3	NM_004369.4	c.6354+1G>A		splice_donor_variant, intron_variant		ENST00000295550.9	NP_004360.2
COL6A3	NM_057167.4	c.5736+1G>A		splice_donor_variant, intron_variant			NP_476508.2
COL6A3	NM_057166.5	c.4533+1G>A		splice_donor_variant, intron_variant			NP_476507.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
COL6A3	ENST00000295550.9	c.6354+1G>A		splice_donor_variant, intron_variant		1	NM_004369.4	ENSP00000295550.4
COL6A3	ENST00000472056.5	c.4533+1G>A		splice_donor_variant, intron_variant		1		ENSP00000418285.1
COL6A3	ENST00000353578.9	c.5736+1G>A		splice_donor_variant, intron_variant		5		ENSP00000315873.4

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 34

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:5 Other:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:3

Pathogenic, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Dec 19, 2020	- -
Pathogenic, criteria provided, single submitter	clinical testing	Eurofins Ntd Llc (ga)	Jan 08, 2018	- -
Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Dec 20, 2023	Observed in the heterozygous state in one patient with Bethlem myopathy in published literature; however, no further phenotypic information was provided (PMID: 28688748); Canonical splice site variant predicted to result in an in-frame loss of the adjacent exon in a gene for which loss of function is a known mechanism of disease; Not observed at significant frequency in large population cohorts (gnomAD); Deletions involving coding exons of this gene are a known mechanism of disease (HGMD); This variant is associated with the following publications: (PMID: 30564623, 28688748, Farkosh2021[Case_Report]) -

Inborn genetic diseases Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Feb 10, 2021

The c.6354+1G>A intronic variant results from a G to A substitution one nucleotide after exon 19 (coding exon 18) of the COL6A3 gene. Alterations that disrupt the canonical splice site are expected to result in aberrant splicing. The resulting transcript is predicted to be in-frame and is not expected to trigger nonsense-mediated mRNA decay; however, direct evidence is unavailable. The exact functional effect of the missing amino acids is unknown; however, the impacted region is critical for protein function (Ambry internal data). Based on the supporting evidence, this variant is expected to be causative of autosomal dominant muscular dystrophy; however, its clinical significance for autosomal recessive disease is unclear. Based on data from the Genome Aggregation Database (gnomAD), the COL6A3 c.6354+1G>A alteration was not observed, with coverage at this position. In a cohort of patients with congenital muscular dystrophy, one individual was reported to be heteroyzgous for this alteration (Sframeli, 2017). In addition, this alteration segregated with autosomal dominant disease in one family (Ambry internal data). This nucleotide position is highly conserved in available vertebrate species. The c.6354+1G>A alteration is located within the triple-helical domain of the collagen alpha-3(VI) chain and is predicted to impact a number of highly conserved glycine residues in the Gly-X-Y motif that make up this domain (Ramshaw, 1998). In silico splice site analysis predicts that this alteration will weaken the native splice donor site. Based on the available evidence, this alteration is classified as likely pathogenic. -

Bethlem myopathy 1A Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Sep 21, 2023

Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. This variant is not present in population databases (gnomAD no frequency). Disruption of this splice site has been observed in individuals with Bethlem myopathy (PMID: 28688748; Invitae). ClinVar contains an entry for this variant (Variation ID: 285748). For these reasons, this variant has been classified as Pathogenic. This sequence change affects a donor splice site in intron 19 of the COL6A3 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 COL6A3 are known to be disease-causing for autosomal recessive COL6A3-related conditions (PMID: 21280092, 20976770). However, certain variants affecting donor or acceptor splice sites in the triple helical domain of COL6A3 are expected to result in in-frame exon skipping and have been reported to cause autosomal dominant COL6A3-related conditions (PMID: 18366090). -

Ullrich congenital muscular dystrophy 1A;CN029274:Bethlem myopathy 1A Other:1

not provided, no classification provided

phenotyping only

GenomeConnect, ClinGen

-

Variant interpretted as Pathogenic and reported on 12-13-2017 by Lab or GTR ID 26957. GenomeConnect assertions are reported exactly as they appear on the patient-provided report from the testing laboratory. GenomeConnect staff make no attempt to reinterpret the clinical significance of the variant. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.24	D
BayesDel_noAF	Uncertain	0.10
CADD	Pathogenic	29
DANN	Uncertain	0.98
Eigen	Pathogenic	0.90
Eigen_PC	Pathogenic	0.67
FATHMM_MKL	Pathogenic	0.99	D
GERP RS		5.1

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.89
SpliceAI score (max)		0.99		Details are displayed if max score is > 0.2
DS_DG_spliceai		0.23		Position offset: 9
DS_DL_spliceai		0.99		Position offset: 1

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs886042883; hg19: chr2-238267848;