2-227164728-T-G

Variant names:

• chr2-227164728-T-G
• rs1553725815
• NM_000091.5:c.2T>G

Variant summary

Our verdict is Pathogenic. The variant received 12 ACMG points: 12P and 0B. PVS1 PS1_Moderate PM2

The NM_000091.5(COL4A3):​c.2T>G​(p.Met1?) variant causes a start lost change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000726 in 1,378,204 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 7.3e-7 (0 hom.)
• Consequence: COL4A3 NM_000091.5 start_lost
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 0.421
• Publications: 0 publications found

Genes affected

COL4A3 (HGNC:2204): (collagen type IV alpha 3 chain) Type IV collagen, the major structural component of basement membranes, is a multimeric protein composed of 3 alpha subunits. These subunits are encoded by 6 different genes, alpha 1 through alpha 6, each of which can form a triple helix structure with 2 other subunits to form type IV collagen. This gene encodes alpha 3. In the Goodpasture syndrome, autoantibodies bind to the collagen molecules in the basement membranes of alveoli and glomeruli. The epitopes that elicit these autoantibodies are localized largely to the non-collagenous C-terminal domain of the protein. A specific kinase phosphorylates amino acids in this same C-terminal region and the expression of this kinase is upregulated during pathogenesis. This gene is also linked to an autosomal recessive form of Alport syndrome. The mutations contributing to this syndrome are also located within the exons that encode this C-terminal region. Like the other members of the type IV collagen gene family, this gene is organized in a head-to-head conformation with another type IV collagen gene so that each gene pair shares a common promoter. [provided by RefSeq, Jun 2010]

COL4A4 (HGNC:2206): (collagen type IV alpha 4 chain) This gene encodes one of the six subunits of type IV collagen, the major structural component of basement membranes. This particular collagen IV subunit, however, is only found in a subset of basement membranes. Like the other members of the type IV collagen gene family, this gene is organized in a head-to-head conformation with another type IV collagen gene so that each gene pair shares a common promoter. Mutations in this gene are associated with type II autosomal recessive Alport syndrome (hereditary glomerulonephropathy) and with familial benign hematuria (thin basement membrane disease). Two transcripts, differing only in their transcription start sites, have been identified for this gene and, as is common for collagen genes, multiple polyadenylation sites are found in the 3' UTR. [provided by RefSeq, Jul 2008]

COL4A4 Gene-Disease associations (from GenCC):

• autosomal recessive Alport syndrome

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Labcorp Genetics (formerly Invitae), Genomics England PanelApp, G2P, Orphanet, Ambry Genetics, Myriad Women’s Health
• Alport syndrome

  Inheritance: SD Classification: DEFINITIVE Submitted by: ClinGen
• hematuria, benign familial, 1

  Inheritance: AD Classification: STRONG, MODERATE Submitted by: Labcorp Genetics (formerly Invitae), Genomics England PanelApp, Ambry Genetics
• autosomal dominant Alport syndrome

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Pathogenic. The variant received 12 ACMG points.

• PVS1: Start lost variant, next in-frame start position is after 83 pathogenic variants. Next in-frame start position is after 209 codons. Genomic position: 227251351. Lost 0.125 part of the original CDS.
• PS1: Another start lost variant in NM_000091.5 (COL4A3) was described as [Likely_pathogenic] in ClinVar
• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
COL4A3	NM_000091.5	c.2T>G	p.Met1?	start_lost	Exon 1 of 52	ENST00000396578.8	NP_000082.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
COL4A3	ENST00000396578.8	c.2T>G	p.Met1?	start_lost	Exon 1 of 52	1	NM_000091.5	ENSP00000379823.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 7.26e-7 AC: 1 AN: 1378204 Hom.: 0 Cov.: 31 AF XY: 0.00000147 AC XY: 1 AN XY: 680080

African (AFR) AF: 0.00 AC: 0 AN: 30958

American (AMR) AF: 0.00 AC: 0 AN: 35598

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 25062

East Asian (EAS) AF: 0.00 AC: 0 AN: 35422

South Asian (SAS) AF: 0.00 AC: 0 AN: 78950

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 33452

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 4058

European-Non Finnish (NFE) AF: 9.28e-7 AC: 1 AN: 1077166

Other (OTH) AF: 0.00 AC: 0 AN: 57538

GnomAD4 genome Cov.: 32

Alfa AF: 0.00 Hom.: 0

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.25
CADD	Benign	18
DANN	Benign	0.93
DEOGEN2	Benign	0.081	T
Eigen	Benign	-0.36
Eigen_PC	Benign	-0.37
FATHMM_MKL	Benign	0.51	D
LIST_S2	Uncertain	0.90	D
M_CAP	Pathogenic	0.98	D
MetaRNN	Pathogenic	0.98	D
MetaSVM	Uncertain	0.14	D
PhyloP100		0.42
PROVEAN	Benign	0.070	N
REVEL	Uncertain	0.55
Sift	Uncertain	0.0040	D
Sift4G	Uncertain	0.0050	D
Polyphen		0.14	B
Vest4		0.83
MutPred		0.92		Gain of MoRF binding (P = 0.0065);
MVP		0.78
ClinPred		0.81	D
GERP RS		4.0
PromoterAI		-0.017	Neutral
Varity_R		0.90
gMVP		0.88
Mutation Taster		=3/197	disease causing

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		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: rs1553725815; hg19: chr2-228029444;