1-94014685-G-T

Position:

• chr1-94014685-G-T

Variant summary

Our verdict is Pathogenic. Variant got 10 ACMG points: 10P and 0B. PM1 PM2 PM5 PP3_Moderate PP5_Moderate

The NM_000350.3(ABCA4):​c.5318C>A​(p.Ala1773Glu) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000342 in 1,461,872 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 Pathogenic (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A1773?) has been classified as Pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000034 (0 hom.)
• Consequence: ABCA4 NM_000350.3 missense
• Clinical Significance: Pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 10.0

Genes affected

ABCA4 (HGNC:34): (ATP binding cassette subfamily A member 4) The membrane-associated protein encoded by this gene is a member of the superfamily of ATP-binding cassette (ABC) transporters. ABC proteins transport various molecules across extra- and intracellular membranes. ABC genes are divided into seven distinct subfamilies (ABC1, MDR/TAP, MRP, ALD, OABP, GCN20, White). This protein is a member of the ABC1 subfamily. Members of the ABC1 subfamily comprise the only major ABC subfamily found exclusively in multicellular eukaryotes. This protein is a retina-specific ABC transporter with N-retinylidene-PE as a substrate. It is expressed exclusively in retina photoreceptor cells, and the gene product mediates transport of an essental molecule, all-trans-retinal aldehyde (atRAL), across the photoreceptor cell membrane. Mutations in this gene are found in patients diagnosed with Stargardt disease, a form of juvenile-onset macular degeneration. Mutations in this gene are also associated with retinitis pigmentosa-19, cone-rod dystrophy type 3, early-onset severe retinal dystrophy, fundus flavimaculatus, and macular degeneration age-related 2. [provided by RefSeq, Sep 2019]

ACMG classification

Verdict is Pathogenic. Variant got 10 ACMG points.

• PM1: In a transmembrane_region Helical (size 20) in uniprot entity ABCA4_HUMAN there are 32 pathogenic changes around while only 0 benign (100%) in NM_000350.3
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr1-94014684-CGC-CT is described in Lovd as [Pathogenic].
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.92
• PP5: Variant 1-94014685-G-T is Pathogenic according to our data. Variant chr1-94014685-G-T is described in ClinVar as [Pathogenic]. Clinvar id is 940353.Status of the report is criteria_provided_single_submitter, 1 stars. Variant chr1-94014685-G-T is described in Lovd as [Likely_pathogenic]. Variant chr1-94014685-G-T is described in Lovd as [Likely_pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
ABCA4	NM_000350.3	c.5318C>A	p.Ala1773Glu	missense_variant	38/50	ENST00000370225.4	NP_000341.2
ABCA4	XM_047416704.1	c.5096C>A	p.Ala1699Glu	missense_variant	37/49		XP_047272660.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
ABCA4	ENST00000370225.4	c.5318C>A	p.Ala1773Glu	missense_variant	38/50	1	NM_000350.3	ENSP00000359245	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000342 AC: 5 AN: 1461872 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 727236

Gnomad4 AFR exome AF: 0.00

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: 0.0000187

Gnomad4 NFE exome AF: 0.00000360

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Oct 13, 2022

This variant disrupts the p.Ala1773 amino acid residue in ABCA4. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 18652558, 23419329, 28130426, 29422768). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. For these reasons, this variant has been classified as Pathogenic. Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt ABCA4 protein function. ClinVar contains an entry for this variant (Variation ID: 940353). This missense change has been observed in individuals with clinical features of Stargardt disease (PMID: 23143460, 30834176). This variant is not present in population databases (gnomAD no frequency). This sequence change replaces alanine, which is neutral and non-polar, with glutamic acid, which is acidic and polar, at codon 1773 of the ABCA4 protein (p.Ala1773Glu). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.95
BayesDel_addAF	Pathogenic	0.42	D
BayesDel_noAF	Pathogenic	0.36
CADD	Pathogenic	27
DANN	Uncertain	0.99
DEOGEN2	Uncertain	0.73	D;D
Eigen	Pathogenic	0.85
Eigen_PC	Pathogenic	0.75
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Uncertain	0.97	D;D
M_CAP	Uncertain	0.13	D
MetaRNN	Pathogenic	0.92	D;D
MetaSVM	Uncertain	0.62	D
MutationAssessor	Uncertain	2.8	.;M
MutationTaster	Benign	1.0	D;D
PrimateAI	Uncertain	0.54	T
PROVEAN	Benign	-1.9	.;N
REVEL	Pathogenic	0.81
Sift	Uncertain	0.0020	.;D
Sift4G	Uncertain	0.0020	D;D
Polyphen		0.99	.;D
Vest4		0.94
MutPred		0.74		.;Gain of helix (P = 0.0696);
MVP		0.97
MPC		0.45
ClinPred		0.99	D
GERP RS		4.7
Varity_R		0.94
gMVP		0.99

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.050		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: rs760549861; hg19: chr1-94480241;