21-45504469-C-G

Position:

• chr21-45504469-C-G

Variant summary

Our verdict is Likely benign. Variant got -6 ACMG points: 0P and 6B. BP4_Strong BP6 BP7

The NM_001379500.1(COL18A1):​c.2781C>G​(p.Pro927Pro) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000117 in 1,456,994 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Synonymous variant affecting the same amino acid position (i.e. P927P) has been classified as Benign.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.000012 (0 hom.)
• Consequence: COL18A1 NM_001379500.1 synonymous
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:1 B:1
• Conservation: PhyloP100: -4.14

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]

SLC19A1 (HGNC:10937): (solute carrier family 19 member 1) The membrane protein encoded by this gene is a transporter of folate and is involved in the regulation of intracellular concentrations of folate. Three transcript variants encoding different isoforms have been found for this gene.[provided by RefSeq, Mar 2011]

ACMG classification

Verdict is Likely_benign. Variant got -6 ACMG points.

• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.8).
• BP6: Variant 21-45504469-C-G is Benign according to our data. Variant chr21-45504469-C-G is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 895262.We mark this variant Likely_benign, oryginal submissions are: {Likely_benign=1, Uncertain_significance=1}.
• BP7: Synonymous conserved (PhyloP=-4.14 with no splicing effect.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
COL18A1	NM_001379500.1	c.2781C>G	p.Pro927Pro	synonymous_variant	34/42	ENST00000651438.1	NP_001366429.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
COL18A1	ENST00000651438.1	c.2781C>G	p.Pro927Pro	synonymous_variant	34/42		NM_001379500.1	ENSP00000498485.1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD3 exomes AF: 0.0000169 AC: 4 AN: 236534 Hom.: 0 AF XY: 0.0000153 AC XY: 2 AN XY: 130688

Gnomad AFR exome AF: 0.0000743

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000189

Gnomad OTH exome AF: 0.000174

GnomAD4 exome AF: 0.0000117 AC: 17 AN: 1456994 Hom.: 0 Cov.: 32 AF XY: 0.0000110 AC XY: 8 AN XY: 724770

Gnomad4 AFR exome AF: 0.0000299

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000135

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome Cov.: 33

Alfa AF: 0.0000365 Hom.: 14

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:1 Benign:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Knobloch syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 13, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

not provided Benign:1

Likely benign, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Oct 13, 2023

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.80
CADD	Benign	0.027
DANN	Benign	0.59

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: rs11544970; hg19: chr21-46924383;