21-45507575-A-C

Variant names:

• chr21-45507575-A-C
• rs12483761
• NM_001379500.1:c.3231A>C

Variant summary

Our verdict is Likely benign. The variant received -3 ACMG points: 2P and 5B. PM2 BP4_Strong BP7

The NM_001379500.1(COL18A1):​c.3231A>C​(p.Thr1077Thr) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000685 in 1,460,492 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. Synonymous variant affecting the same amino acid position (i.e. T1077T) has been classified as Benign.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: COL18A1 NM_001379500.1 synonymous
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: -3.53
• Publications: 10 publications found

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]

SLC19A1 Gene-Disease associations (from GenCC):

• combined immunodeficiency

  Inheritance: AR Classification: MODERATE Submitted by: PanelApp Australia
• immunodeficiency 114, folate-responsive

  Inheritance: AR Classification: LIMITED Submitted by: ClinGen
• megaloblastic anemia, folate-responsive

  Inheritance: AR Classification: LIMITED Submitted by: PanelApp Australia

ACMG classification

Our verdict: Likely_benign. The variant received -3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (BayesDel_noAF=-1.01).
• BP7: Synonymous conserved (PhyloP=-3.53 with no splicing effect.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_001379500.1. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	COL18A1	NM_001379500.1	MANE Select	c.3231A>C	p.Thr1077Thr	synonymous	Exon 38 of 42	NP_001366429.1	P39060-2
	COL18A1	NM_130444.3		c.4476A>C	p.Thr1492Thr	synonymous	Exon 37 of 41	NP_569711.2
	COL18A1	NM_030582.4		c.3771A>C	p.Thr1257Thr	synonymous	Exon 37 of 41	NP_085059.2	A0AAG2UXZ5

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	COL18A1	ENST00000651438.1	MANE Select	c.3231A>C	p.Thr1077Thr	synonymous	Exon 38 of 42	ENSP00000498485.1	P39060-2
	COL18A1	ENST00000355480.10	TSL:1	c.3771A>C	p.Thr1257Thr	synonymous	Exon 37 of 41	ENSP00000347665.5	P39060-1
	SLC19A1	ENST00000567670.5	TSL:1	c.1294-8963T>G		intron	N/A	ENSP00000457278.1	H3BTQ3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD2 exomes AF: 0.00000406 AC: 1 AN: 246296 AF XY: 0.00000745

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: 0.00000898

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 6.85e-7 AC: 1 AN: 1460492 Hom.: 0 Cov.: 33 AF XY: 0.00000138 AC XY: 1 AN XY: 726514

African (AFR) AF: 0.00 AC: 0 AN: 33468

American (AMR) AF: 0.00 AC: 0 AN: 44634

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26132

East Asian (EAS) AF: 0.00 AC: 0 AN: 39696

South Asian (SAS) AF: 0.00 AC: 0 AN: 86208

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 52522

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5736

European-Non Finnish (NFE) AF: 8.99e-7 AC: 1 AN: 1111744

Other (OTH) AF: 0.00 AC: 0 AN: 60352

GnomAD4 genome Cov.: 33

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-1.0
CADD	Benign	0.36
DANN	Benign	0.66
PhyloP100		-3.5

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

Other links and lift over

dbSNP: rs12483761; hg19: chr21-46927489;