6-75103800-C-T

Variant summary

Our verdict is Likely pathogenic. Variant got 9 ACMG points: 9P and 0B. PM1 PM2 PP2 PP3_Strong

The NM_004370.6(COL12A1):c.8276G>A(p.Gly2759Asp) variant causes a missense change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Synonymous variant affecting the same amino acid position (i.e. G2759G) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 32)
• Consequence: COL12A1 NM_004370.6 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 6.39

Genes affected

COL12A1 (HGNC:2188): (collagen type XII alpha 1 chain) This gene encodes the alpha chain of type XII collagen, a member of the FACIT (fibril-associated collagens with interrupted triple helices) collagen family. Type XII collagen is a homotrimer found in association with type I collagen, an association that is thought to modify the interactions between collagen I fibrils and the surrounding matrix. Alternatively spliced transcript variants encoding different isoforms have been identified. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Likely_pathogenic. Variant got 9 ACMG points.

• PM1: In a domain Collagen-like 1 (size 51) in uniprot entity COCA1_HUMAN there are 7 pathogenic changes around while only 1 benign (88%) in NM_004370.6
• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant where missense usually causes diseases, COL12A1
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.986

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
COL12A1	NM_004370.6	c.8276G>A	p.Gly2759Asp	missense_variant	55/66	ENST00000322507.13

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
COL12A1	ENST00000322507.13	c.8276G>A	p.Gly2759Asp	missense_variant	55/66	1	NM_004370.6	P4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 29

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Bethlem myopathy 2;C4225314:Ullrich congenital muscular dystrophy 2 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Jul 04, 2019

In summary, this variant is a novel missense change affecting a residue that is critical for protein structure, stability and function. However, the available evidence is currently insufficient to determine its role in disease. Therefore, it has been classified as a Variant of Uncertain Significance. Glycine residues within the Gly-Xaa-Yaa repeats of the triple helix domain are required for the structure and stability of fibrillar collagens (PMID: 7695699, 8218237, 19344236), and missense variants at these glycine residues in COL12A1 are more frequently observed in individuals with disease than in the general population (PMID: 10612821). However, the clinical significance of this observation remains uncertain since only a limited number of affected individuals have been described to date. Algorithms developed to predict the effect of missense changes on protein structure and function do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). This variant is not present in population databases (ExAC no frequency) and has not been reported in the literature in individuals with a COL12A1-related disease. This sequence change replaces glycine with aspartic acid at codon 2759 of the COL12A1 protein (p.Gly2759Asp). The glycine residue is highly conserved and there is a moderate physicochemical difference between glycine and aspartic acid. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.52	D
BayesDel_noAF	Pathogenic	0.51
Cadd	Pathogenic	29
Dann	Uncertain	1.0
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	0.95
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.91	D;D;D;D;D;D
M_CAP	Pathogenic	0.47	D
MetaRNN	Pathogenic	0.99	D;D;D;D;D;D
MetaSVM	Pathogenic	0.98	D
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Pathogenic	0.90	D
PROVEAN	Pathogenic	-5.7	D;.;D;D;D;D
REVEL	Pathogenic	0.94
Sift	Uncertain	0.0020	D;.;D;D;D;D
Sift4G	Pathogenic	0.0	D;D;D;D;D;D
Polyphen		1.0	.;.;D;D;.;.
Vest4		0.75, 0.87, 0.89, 0.91, 0.91
MutPred		0.92		.;.;Gain of relative solvent accessibility (P = 0.0023);.;.;Gain of relative solvent accessibility (P = 0.0023);
MVP		0.95
MPC		1.6
ClinPred		0.99	D
GERP RS		5.5
Varity_R		0.99
gMVP		0.99

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		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

Other links and lift over

dbSNP: rs1554168599; hg19: chr6-75813516;