chr21-45419989-T-G

Variant names:

• chr21-45419989-T-G
• rs2838917
• ENST00000397787.5:n.3152A>C

Variant summary

Our verdict is Likely benign. The variant received -2 ACMG points: 2P and 4B. PM2 BP4_Strong

The ENST00000397787.5(COL18A1-AS1):​n.3152A>C variant causes a non coding transcript exon change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000132 in 152,082 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar.

• Frequency: Genomes: 𝑓 0.000013 (0 hom., cov: 32)
• Consequence: COL18A1-AS1 ENST00000397787.5 non_coding_transcript_exon
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 0.313
• Publications: 14 publications found

Genes affected

COL18A1-AS1 (HGNC:23132): (COL18A1 antisense RNA 1)

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

ACMG classification

Our verdict: Likely_benign. The variant received -2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.91).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
COL18A1	NM_001379500.1	c.106+14516T>G		intron_variant	Intron 2 of 41	ENST00000651438.1	NP_001366429.1
COL18A1-AS1	NR_027498.1	n.2068A>C		non_coding_transcript_exon_variant	Exon 3 of 3
COL18A1-AS1	NR_028082.1	n.3152A>C		non_coding_transcript_exon_variant	Exon 3 of 3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
COL18A1-AS1	ENST00000397787.5	n.3152A>C		non_coding_transcript_exon_variant	Exon 3 of 3	1
COL18A1-AS1	ENST00000485206.1	n.2068A>C		non_coding_transcript_exon_variant	Exon 3 of 3	1
COL18A1	ENST00000651438.1	c.106+14516T>G		intron_variant	Intron 2 of 41		NM_001379500.1	ENSP00000498485.1

Frequencies

GnomAD3 genomes AF: 0.0000132 AC: 2 AN: 151962 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.000388

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.00

Gnomad OTH AF: 0.00

GnomAD4 exome Cov.: 0

GnomAD4 genome AF: 0.0000132 AC: 2 AN: 152082 Hom.: 0 Cov.: 32 AF XY: 0.0000135 AC XY: 1 AN XY: 74348

African (AFR) AF: 0.00 AC: 0 AN: 41474

American (AMR) AF: 0.00 AC: 0 AN: 15272

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3472

East Asian (EAS) AF: 0.000389 AC: 2 AN: 5138

South Asian (SAS) AF: 0.00 AC: 0 AN: 4822

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10594

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 294

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 67992

Other (OTH) AF: 0.00 AC: 0 AN: 2114

Alfa AF: 0.00 Hom.: 135089

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.91
CADD	Benign	3.3
DANN	Benign	0.37
PhyloP100		0.31

Splicing

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

Other links and lift over

dbSNP: rs2838917; hg19: chr21-46839904;