Genetic Variant COL18A1:p.Gly532ArgfsTer29 (chr21-45480834-T-TC) – ACMG Classification: Pathogenic (10 pts)

Variant summary

Our verdict is Pathogenic. The variant received 10 ACMG points: 10P and 0B. PVS1PM2

The NM_001379500.1(COL18A1):c.1593dupC(p.Gly532ArgfsTer29) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000274 in 1,458,962 control chromosomes in the GnomAD database, with no homozygous occurrence. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Synonymous variant affecting the same amino acid position (i.e. G532G) has been classified as Likely benign. Variant results in nonsense mediated mRNA decay.

Frequency

Genomes: not found (cov: 33)

Exomes 𝑓: 0.0000027 ( 0 hom. )

Consequence

COL18A1
NM_001379500.1 frameshift

Scores

Not classified

Clinical Significance

Not reported in ClinVar

Conservation

PhyloP100: -1.61

Publications

0 publications found

Variant links:

Genes affected

COL18A1 (HGNC:2195): (collagen type XVIII alpha 1 chain) This gene encodes the alpha chain of type XVIII collagen. This collagen is one of the multiplexins, extracellular matrix proteins that contain multiple triple-helix domains (collagenous domains) interrupted by non-collagenous domains. A long isoform of the protein has an N-terminal domain that is homologous to the extracellular part of frizzled receptors. Proteolytic processing at several endogenous cleavage sites in the C-terminal domain results in production of endostatin, a potent antiangiogenic protein that is able to inhibit angiogenesis and tumor growth. Mutations in this gene are associated with Knobloch syndrome. The main features of this syndrome involve retinal abnormalities, so type XVIII collagen may play an important role in retinal structure and in neural tube closure. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Dec 2014]

COL18A1 Gene-Disease associations (from GenCC):

Knobloch syndrome 1
Inheritance: AR Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), ClinGen, G2P
Knobloch syndrome
Inheritance: AR Classification: STRONG, SUPPORTIVE Submitted by: Laboratory for Molecular Medicine, Orphanet
hereditary glaucoma, primary closed-angle
Inheritance: AD Classification: LIMITED Submitted by: Ambry Genetics

COL18A1 links:

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ACMG classification

Classification was made for transcript

Our verdict: Pathogenic. The variant received 10 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;

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein
COL18A1	NM_001379500.1 link	c.1593dupC	p.Gly532ArgfsTer29	frameshift_variant	Exon 13 of 42	ENST00000651438.1	NP_001366429.1
COL18A1	NM_130444.3 link	c.2838dupC	p.Gly947ArgfsTer29	frameshift_variant	Exon 12 of 41		NP_569711.2
COL18A1	NM_030582.4 link	c.2133dupC	p.Gly712ArgfsTer29	frameshift_variant	Exon 12 of 41		NP_085059.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein
COL18A1	ENST00000651438.1 link	c.1593dupC	p.Gly532ArgfsTer29	frameshift_variant	Exon 13 of 42		NM_001379500.1	ENSP00000498485.1
COL18A1	ENST00000355480.10 link	c.2133dupC	p.Gly712ArgfsTer29	frameshift_variant	Exon 12 of 41	1		ENSP00000347665.5
COL18A1	ENST00000359759.8 link	c.2838dupC	p.Gly947ArgfsTer29	frameshift_variant	Exon 12 of 41	5		ENSP00000352798.4

Frequencies

GnomAD3 genomes

Cov.:

GnomAD2 exomes

AF:

0.00

AC:

AN:

240838

AF XY:

0.00

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000274

AC:

AN:

1458962

Hom.:

Cov.:

AF XY:

0.00000138

AC XY:

AN XY:

725796

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

33450

American (AMR)

AF:

0.00

AC:

AN:

44616

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26064

East Asian (EAS)

AF:

0.00

AC:

AN:

39654

South Asian (SAS)

AF:

0.00

AC:

AN:

86052

European-Finnish (FIN)

AF:

0.0000194

AC:

AN:

51632

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5756

European-Non Finnish (NFE)

AF:

0.00000270

AC:

AN:

1111490

Other (OTH)

AF:

0.00

AC:

AN:

60248

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.425

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

Cov.:

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

PhyloP100

-1.6

Splicing

Name

Calibrated prediction

Score

Prediction

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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21-45480834-TC-TCC

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

ClinVar

Computational scores

Splicing

Publications

Other links and lift over