21-45405236-GC-G

Position:

• chr21-45405236-GC-G

Variant summary

Our verdict is Pathogenic. Variant got 10 ACMG points: 10P and 0B. PVS1 PP5_Moderate

The NM_001379500.1(COL18A1):​c.8del​(p.Pro3ArgfsTer121) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. Variant has been reported in ClinVar as Pathogenic (★). Synonymous variant affecting the same amino acid position (i.e. P3P) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 0)
• Consequence: COL18A1 NM_001379500.1 frameshift
• Clinical Significance: Pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 0.495

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]

BNAT1 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 10 ACMG points.

• PVS1: Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant located near the start codon (<100nt), not predicted to undergo nonsense mediated mRNA decay. There are 83 pathogenic variants in the truncated region.
• PP5: Variant 21-45405236-GC-G is Pathogenic according to our data. Variant chr21-45405236-GC-G is described in ClinVar as [Pathogenic]. Clinvar id is 1452520.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
COL18A1	NM_001379500.1	c.8del	p.Pro3ArgfsTer121	frameshift_variant	1/42	ENST00000651438.1
BNAT1	NR_183526.1	n.197-741del		intron_variant, non_coding_transcript_variant
BNAT1	NR_183527.1	n.181+123del		intron_variant, non_coding_transcript_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
COL18A1	ENST00000651438.1	c.8del	p.Pro3ArgfsTer121	frameshift_variant	1/42		NM_001379500.1

Frequencies

GnomAD3 genomes Cov.: 0

GnomAD4 exome Cov.: 3

GnomAD4 genome Cov.: 0

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Nov 28, 2021

This variant has not been reported in the literature in individuals affected with COL18A1-related conditions. For these reasons, this variant has been classified as Pathogenic. This variant is not present in population databases (gnomAD no frequency). This sequence change creates a premature translational stop signal (p.Pro3Argfs*121) in the COL18A1 gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in COL18A1 are known to be pathogenic (PMID: 12415512, 25456301). -

Computational scores

Source: dbNSFP v4.3

Splicing

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

Publications

No publications associated with this variant yet.

Other links and lift over

hg19: chr21-46825151;