NM_001848.3:c.1003-2delA

Variant names:

• chr21-45990770-CA-C
• rs1556425835
• NM_001848.3:c.1003-2delA

Variant summary

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

The NM_001848.3(COL6A1):​c.1003-2delA variant causes a splice acceptor, intron change. The variant was absent in control chromosomes in GnomAD project. 1/1 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Pathogenic (★★).

• Frequency: Genomes: not found (cov: 33)
• Consequence: COL6A1 NM_001848.3 splice_acceptor, intron
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:5
• Conservation: PhyloP100: 5.75

Genes affected

COL6A1 (HGNC:2211): (collagen type VI alpha 1 chain) The collagens are a superfamily of proteins that play a role in maintaining the integrity of various tissues. Collagens are extracellular matrix proteins and have a triple-helical domain as their common structural element. Collagen VI is a major structural component of microfibrils. The basic structural unit of collagen VI is a heterotrimer of the alpha1(VI), alpha2(VI), and alpha3(VI) chains. The alpha2(VI) and alpha3(VI) chains are encoded by the COL6A2 and COL6A3 genes, respectively. The protein encoded by this gene is the alpha 1 subunit of type VI collagen (alpha1(VI) chain). Mutations in the genes that code for the collagen VI subunits result in the autosomal dominant disorder, Bethlem myopathy. [provided by RefSeq, Jul 2008]

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 0.017492712 fraction of the gene. Cryptic splice site detected, with MaxEntScore 6.4, offset of -26, new splice context is: tttacccacttggccgtcAGatt. 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
• PP5: Variant 21-45990770-CA-C is Pathogenic according to our data. Variant chr21-45990770-CA-C is described in ClinVar as [Pathogenic]. Clinvar id is 476406.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr21-45990770-CA-C is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
COL6A1	NM_001848.3	c.1003-2delA		splice_acceptor_variant, intron_variant	Intron 13 of 34	ENST00000361866.8	NP_001839.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
COL6A1	ENST00000361866.8	c.1003-2delA		splice_acceptor_variant, intron_variant	Intron 13 of 34	1	NM_001848.3	ENSP00000355180.3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 34

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:5

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:3

Mar 20, 2017

Eurofins Ntd Llc (ga)

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Aug 16, 2019

Revvity Omics, Revvity

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Jun 17, 2019

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Published RNA functional studies show that this variant results in the in-frame excision of exon 14, located within the triple helical region (Cruz et al., 2016); Deletions involving coding exons in this gene are frequently reported as pathogenic, regardless of frame prediction (Stenson et al., 2014); Not observed in large population cohorts (Lek et al., 2016); This variant is associated with the following publications: (PMID: 27854213) -

Bethlem myopathy 1A Pathogenic:2

Nov 13, 2023

3billion

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The variant is not observed in the gnomAD v2.1.1 dataset. Predicted Consequence/Location: Canonical splice site: predicted to alter splicing and result in a loss or disruption of normal protein function. Multiple pathogenic loss-of-function variants are reported downstream of the variant. In silico tools predict the variant to alter splicing and produce an abnormal transcript [Splice AI: 0.98 (spliceogenicity >=0.2, non-spliceogenicity <0.1)]. The variant has been reported at least twice as pathogenic with clinical assertions and evidence for the classification (ClinVar ID: VCV000476406). Therefore, this variant is classified as Pathogenic according to the recommendation of ACMG/AMP guideline. -

Dec 26, 2017

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

For these reasons, this variant has been classified as Pathogenic. Donor and acceptor splice site variants typically lead to a loss of protein function (PMID: 16199547), and loss-of-function variants in COL6A1 are known to be pathogenic (PMID: 19884007, 20976770). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site, but this prediction has not been confirmed by published transcriptional studies. This variant has been reported to be de novo in an individual affected with COL6A1-related disease (Invitae). This variant is not present in population databases (ExAC no frequency). This sequence change affects an acceptor splice site in intron 13 of the COL6A1 gene. It is expected to disrupt RNA splicing and likely results in an absent or disrupted protein product. -

Computational scores

Source: dbNSFP v4.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.98		Details are displayed if max score is > 0.2
DS_AL_spliceai		0.98		Position offset: 3

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

Publications

LitVar

Other links and lift over

dbSNP: rs1556425835; hg19: chr21-47410684;