Mutations

APP D244G

Overview

Pathogenicity: Alzheimer's Disease : Not Classified
ACMG/AMP Pathogenicity Criteria: PM2, PP3
Clinical Phenotype: Alzheimer's Disease
Position: (GRCh38/hg38):Chr21:26021974 A>G
Position: (GRCh37/hg19):Chr21:27394290 A>G
dbSNP ID: rs1347585131
Coding/Non-Coding: Coding
DNA Change: Substitution
Expected RNA Consequence: Substitution
Expected Protein Consequence: Missense
Codon Change: GAT to GGT
Reference Isoform: APP Isoform APP770 (770 aa)
Genomic Region: Exon 6

Findings

This variant was identified in a whole-exome sequencing study of Chinese Alzheimer’s cases with a family history consistent with autosomal-dominant inheritance (Jiang et al., 2019). The carrier was 54 years old when she began experiencing memory deficits. Her mother was reported to have shown similar symptoms. Family members were not genotyped, so it is not known whether the variant segregates with disease in this family.

The D244G variant was not found in the ExAC or 1000 Genomes Project databases, or in 500 ethnically  and age-matched controls (Jiang et al., 2019). One heterozygous carrier was found among the East Asian population in gnomAD (v2.1.1, searched 2020-10-14).

Biological Effect

The biological effect of the aspartate-to-glycine substitution has not been tested directly yet. The D244G mutation is predicted to be probably damaging by PolyPhen-2 and tolerated by SIFT (Jiang et al., 2019). The PHRED-scaled CADD score was above 20, suggesting a deleterious effect (CADD v.1.6, Oct 2021).

Pathogenicity

Alzheimer's Disease : Not Classified*

*This variant fulfilled some ACMG-AMP criteria, but it was not classified by Alzforum, because data for either a pathogenic or benign classification are lacking: only one affected carrier has been reported without co-segregation data, and the variant is absent—or very rare—in the gnomAD database.

This variant fulfilled the following criteria based on the ACMG/AMP guidelines. See a full list of the criteria in the Methods page.

PM2-M

Absent from controls (or at extremely low frequency if recessive) in Exome Sequencing Project, 1000 Genomes Project, or Exome Aggregation Consortium. *Alzforum uses the gnomAD variant database.

PP3-P

Multiple lines of computational evidence support a deleterious effect on the gene or gene product (conservation, evolutionary, splicing impact, etc.). *In most cases, Alzforum applies this criterion when the variant’s PHRED-scaled CADD score is greater than or equal to 20.

Pathogenic (PS, PM, PP) Benign (BA, BS, BP)
Criteria Weighting Strong (-S) Moderate (-M) Supporting (-P) Supporting (-P) Strong (-S) Strongest (BA)

Last Updated: 22 Feb 2022

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References

Paper Citations

  1. Jiang B, Zhou J, Li HL, Chen YG, Cheng HR, Ye LQ, Liu DS, Chen DF, Tao QQ, Wu ZY. Mutation screening in Chinese patients with familial Alzheimer's disease by whole-exome sequencing. Neurobiol Aging. 2019 Apr;76:215.e15-215.e21. Epub 2018 Dec 6 PubMed.

External Citations

  1. CADD v.1.6

Further Reading

No Available Further Reading

Protein Diagram

Primary Papers

  1. Jiang B, Zhou J, Li HL, Chen YG, Cheng HR, Ye LQ, Liu DS, Chen DF, Tao QQ, Wu ZY. Mutation screening in Chinese patients with familial Alzheimer's disease by whole-exome sequencing. Neurobiol Aging. 2019 Apr;76:215.e15-215.e21. Epub 2018 Dec 6 PubMed.

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