21-45504478-C-T

Variant names:

• chr21-45504478-C-T
• rs564134000
• NM_001379500.1:c.2790C>T

Variant summary

Our verdict is Benign. Variant got -17 ACMG points: 0P and 17B. BP4_Strong BP6_Very_Strong BP7 BS2

The NM_001379500.1(COL18A1):​c.2790C>T​(p.Gly930Gly) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000232 in 1,603,322 control chromosomes in the GnomAD database, including 2 homozygotes. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Likely benign (★★).

• Frequency:
  • Genomes: 𝑓 0.00077 (0 hom., cov: 33)
  • Exomes 𝑓: 0.00018 (2 hom.)
• Consequence: COL18A1 NM_001379500.1 synonymous
• Clinical Significance: Benign/Likely benign criteria provided, multiple submitters, no conflicts B:4
• Conservation: PhyloP100: -3.46

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 Benign. Variant got -17 ACMG points.

• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.89).
• BP6: Variant 21-45504478-C-T is Benign according to our data. Variant chr21-45504478-C-T is described in ClinVar as [Likely_benign]. Clinvar id is 447122.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• BP7: Synonymous conserved (PhyloP=-3.45 with no splicing effect.
• BS2: High Homozygotes in GnomAdExome4 at 2 AD,AR gene

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
COL18A1	NM_001379500.1	c.2790C>T	p.Gly930Gly	synonymous_variant	Exon 34 of 42	ENST00000651438.1	NP_001366429.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
COL18A1	ENST00000651438.1	c.2790C>T	p.Gly930Gly	synonymous_variant	Exon 34 of 42		NM_001379500.1	ENSP00000498485.1

Frequencies

GnomAD3 genomes AF: 0.000762 AC: 112 AN: 146916 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.00251

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.000136

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00185

Gnomad SAS AF: 0.000218

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000150

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.000468 AC: 110 AN: 235004 Hom.: 1 AF XY: 0.000431 AC XY: 56 AN XY: 129934

Gnomad AFR exome AF: 0.00332

Gnomad AMR exome AF: 0.000472

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00114

Gnomad SAS exome AF: 0.000763

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000479

Gnomad OTH exome AF: 0.000350

GnomAD4 exome AF: 0.000178 AC: 259 AN: 1456294 Hom.: 2 Cov.: 32 AF XY: 0.000178 AC XY: 129 AN XY: 724374

Gnomad4 AFR exome AF: 0.00327

Gnomad4 AMR exome AF: 0.000494

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.000580

Gnomad4 SAS exome AF: 0.000860

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000126

Gnomad4 OTH exome AF: 0.000267

GnomAD4 genome AF: 0.000769 AC: 113 AN: 147028 Hom.: 0 Cov.: 33 AF XY: 0.000726 AC XY: 52 AN XY: 71588

Gnomad4 AFR AF: 0.00253

Gnomad4 AMR AF: 0.000136

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00186

Gnomad4 SAS AF: 0.000218

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.0000150

Gnomad4 OTH AF: 0.00

Alfa AF: 0.000290 Hom.: 0

Bravo AF: 0.000979

ClinVar

Significance: Benign/Likely benign

Submissions summary: Benign:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Benign:2

Jan 27, 2025

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

-

Breakthrough Genomics, Breakthrough Genomics

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: not provided

- -

not specified Benign:1

Jun 27, 2017

Athena Diagnostics

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Knobloch syndrome Benign:1

Jan 13, 2018

Illumina Laboratory Services, Illumina

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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 and internal cut-off values, a variant classified as likely benign is not then subjected to further curation. The score for this variant resulted in a classification of likely benign for this disease. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.89
CADD	Benign	0.30
DANN	Benign	0.63
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs564134000; hg19: chr21-46924392; COSMIC: COSV60592014; COSMIC: COSV60592014;