2-227164727-A-C

Variant names:

• chr2-227164727-A-C
• rs1396602090
• NM_000091.5:c.1A>C

Variant summary

Our verdict is Pathogenic. Variant got 20 ACMG points: 20P and 0B. PVS1 PS1_Moderate PM2 PP5_Very_Strong

The NM_000091.5(COL4A3):​c.1A>C​(p.Met1?) variant causes a initiator codon change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000659 in 151,792 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency: Genomes: 𝑓 0.0000066 (0 hom., cov: 32)
• Consequence: COL4A3 NM_000091.5 initiator_codon
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:4
• Conservation: PhyloP100: 1.39

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]

ACMG classification

Verdict is Pathogenic. Variant got 20 ACMG points.

• PVS1: Start lost variant, next in-frame start position is after 20 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 [Pathogenic] in Lovd
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 2-227164727-A-C is Pathogenic according to our data. Variant chr2-227164727-A-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 555012.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
COL4A3	NM_000091.5	c.1A>C	p.Met1?	initiator_codon_variant	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.1A>C	p.Met1?	initiator_codon_variant	Exon 1 of 52	1	NM_000091.5	ENSP00000379823.3

Frequencies

GnomAD3 genomes AF: 0.00000659 AC: 1 AN: 151792 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.000196

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.00

Gnomad OTH AF: 0.00

GnomAD4 exome Cov.: 31

GnomAD4 genome AF: 0.00000659 AC: 1 AN: 151792 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 74140

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.000196

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.00

Bravo AF: 0.00000378

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Autosomal recessive Alport syndrome Pathogenic:2

May 22, 2022

3billion, Medical Genetics

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The variant is not observed in the gnomAD v2.1.1 dataset. Start-lost: reinitiation of translation may occur at a downstream alternate start codon but still result in a loss or disruption of normal protein function as there have been pathogenic variants reported upstream of the alterante start codon. The variant has been reported at least twice as pathogenic (ClinVar ID: VCV000555012). Therefore, this variant is classified as likely pathogenic according to the recommendation of ACMG/AMP guideline. -

Nov 13, 2017

Counsyl

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Alport syndrome Pathogenic:1

Feb 02, 2022

Victorian Clinical Genetics Services, Murdoch Childrens Research Institute

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Based on the classification scheme VCGS_Germline_v1.3.4, this variant is classified as Pathogenic. Following criteria are met: 0103 - Dominant negative and loss of function are known mechanisms of disease in this gene and are associated with COL4A3-related nephropathy. Glycine changes that are part of a G-X-Y repeat in the triple helix of a collagen domain are known to have a dominant negative effect (PMID: 12028435). (I) 0108 - This gene is associated with both recessive (Alport syndrome 2 MIM#203780) and dominant disease (Alport syndrome 3 MIM#104200 and benign familial hematuria MIM#141200) (OMIM). (I) 0206 - Variant is predicted to result in a loss of the canonical translation initiation codon (ATG). (SP) 0251 - This variant is heterozygous. (I) 0304 - Variant is present in gnomAD (v3) <0.01 for a recessive condition (1 heterozygote, 0 homozygotes). (SP) 0702 - Other canonical translation initiation codon variants comparable to the one identified in this case have strong previous evidence for pathogenicity. Four variants affecting the canonical translation initiation codon have been observed in homozygous or compound heterozygous states in multiple individuals with autosomal recessive Alport syndrome (ClinVar, PMIDs: 12028435, 33772369, 23297803, 24854265). (SP) 0803 - This variant has limited previous evidence of pathogenicity in two unrelated individuals with zygosity unknown (ClinVar). (SP) 0905 - No published segregation evidence has been identified for this variant. (I) 1007 - No published functional evidence has been identified for this variant. (I) 1208 - Inheritance information for this variant is not currently available in this individual. (I) Legend: (SP) - Supporting pathogenic, (I) - Information, (SB) - Supporting benign -

not provided Pathogenic:1

Jun 03, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change affects the initiator methionine of the COL4A3 mRNA. The next in-frame methionine is located at codon 209. This variant is not present in population databases (gnomAD no frequency). Disruption of the initiator codon has been observed in individuals with autosomal recessive Alport syndrome (PMID: 12028435, 23297803, 24854265, 26809805). ClinVar contains an entry for this variant (Variation ID: 555012). For these reasons, this variant has been classified as Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.37	D
BayesDel_noAF	Pathogenic	0.29
CADD	Benign	7.4
DANN	Benign	0.47
DEOGEN2	Benign	0.083	T
Eigen	Benign	-1.0
Eigen_PC	Benign	-1.0
FATHMM_MKL	Benign	0.20	N
LIST_S2	Uncertain	0.90	D
M_CAP	Pathogenic	0.96	D
MetaRNN	Pathogenic	0.98	D
MetaSVM	Benign	-0.48	T
PROVEAN	Benign	-0.33	N
REVEL	Uncertain	0.49
Sift	Benign	0.089	T
Sift4G	Benign	0.44	T
Polyphen		0.0	B
Vest4		0.95
MutPred		0.97		Loss of catalytic residue at M1 (P = 0.1047);
MVP		0.60
ClinPred		0.17	T
GERP RS		1.5
Varity_R		0.25
gMVP		0.61

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

Publications

LitVar

Other links and lift over

dbSNP: rs1396602090; hg19: chr2-228029443;