21-25881476-T-G

Position:

• chr21-25881476-T-G

Variant summary

Our verdict is Benign. Variant got -9 ACMG points: 0P and 9B. BP4_Strong BS1_Supporting BS2

The NM_000484.4(APP):​c.*194A>C variant causes a 3 prime UTR change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000304 in 660,646 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: 𝑓 0.00018 (0 hom., cov: 32)
  • Exomes 𝑓: 0.00034 (0 hom.)
• Consequence: APP NM_000484.4 3_prime_UTR
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: -0.971

Genes affected

APP (HGNC:620): (amyloid beta precursor protein) This gene encodes a cell surface receptor and transmembrane precursor protein that is cleaved by secretases to form a number of peptides. Some of these peptides are secreted and can bind to the acetyltransferase complex APBB1/TIP60 to promote transcriptional activation, while others form the protein basis of the amyloid plaques found in the brains of patients with Alzheimer disease. In addition, two of the peptides are antimicrobial peptides, having been shown to have bacteriocidal and antifungal activities. Mutations in this gene have been implicated in autosomal dominant Alzheimer disease and cerebroarterial amyloidosis (cerebral amyloid angiopathy). Multiple transcript variants encoding several different isoforms have been found for this gene. [provided by RefSeq, Aug 2014]

ACMG classification

Verdict is Benign. Variant got -9 ACMG points.

• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.51).
• BS1: Variant frequency is greater than expected in population eas. gnomad4_exome allele frequency = 0.000342 (174/508436) while in subpopulation EAS AF= 0.00355 (111/31298). AF 95% confidence interval is 0.00301. There are 0 homozygotes in gnomad4_exome. There are 92 alleles in male gnomad4_exome subpopulation. Median coverage is 5. This position pass quality control queck. Existence of Clinvar submissions makes me limit the strength of this signal to Supporting
• BS2: High AC in GnomAd4 at 27 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
APP	NM_000484.4	c.*194A>C		3_prime_UTR_variant	18/18	ENST00000346798.8	NP_000475.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
APP	ENST00000346798.8	c.*194A>C		3_prime_UTR_variant	18/18	1	NM_000484.4	ENSP00000284981

Frequencies

GnomAD3 genomes AF: 0.000177 AC: 27 AN: 152210 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.000338

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.000196

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.000192

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.000132

Gnomad OTH AF: 0.00

GnomAD4 exome AF: 0.000342 AC: 174 AN: 508436 Hom.: 0 Cov.: 5 AF XY: 0.000339 AC XY: 92 AN XY: 271210

Gnomad4 AFR exome AF: 0.000210

Gnomad4 AMR exome AF: 0.0000706

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00355

Gnomad4 SAS exome AF: 0.000190

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.000132

Gnomad4 OTH exome AF: 0.000282

GnomAD4 genome AF: 0.000177 AC: 27 AN: 152210 Hom.: 0 Cov.: 32 AF XY: 0.000175 AC XY: 13 AN XY: 74362

Gnomad4 AFR AF: 0.000338

Gnomad4 AMR AF: 0.000196

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.000192

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.000132

Gnomad4 OTH AF: 0.00

Alfa AF: 0.000214 Hom.: 0

Bravo AF: 0.000132

Asia WGS AF: 0.000577 AC: 2 AN: 3478

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Alzheimer disease Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 12, 2018

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, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.51
CADD	Benign	14
DANN	Benign	0.83

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: rs199977643; hg19: chr21-27253787;