Overview

Pathogenicity: Alzheimer's Disease : Pathogenic
ACMG/AMP Pathogenicity Criteria: PS3, PM1, PM2, PM5, PP2, PP3
Clinical Phenotype: Alzheimer's Disease
Reference Assembly: GRCh37/hg19
Position: Chr14:73664768 C>G
dbSNP ID: NA
Coding/Non-Coding: Coding
DNA Change: Substitution
Expected RNA Consequence: Substitution
Expected Protein Consequence: Missense
Codon Change: CCA to GCA
Reference Isoform: PSEN1 Isoform 1 (467 aa)
Genomic Region: Exon 8

Findings

This mutation was identified in an African-American man with Alzheimer’s disease who had a strong family history of dementia (Ringman et al., 2016). He developed memory problems at age 62 and died at age 69. His identical twin brother was diagnosed with AD at the age of 59 and their mother developed dementia in her mid-60s. The mutation was also identified in another African-American man, thought to be unrelated. He developed symptoms at age 45 and met clinical criteria for AD at age 51. The report notes a strong family history of dementia in this man as well, with evidence of autosomal dominant transmission, but further details were not reported.

This variant was absent from the gnomAD variant database (gnomAD v2.1.1, July 2021).

Neuropathology

Neuropathology is available for one mutation carrier and showed frequent neuritic plaques, including in the neocortex (Braak stage VI), and severe cerebral amyloid angiopathy. Lewy bodies were not present.

Biological Effect

A study that examined a range of Aβ peptides produced by human embryonic kidney cells expressing this mutant and lacking endogenous PSEN1 and PSEN2 revealed increased Aβ42/Aβ40 and decreased Aβ37/Aβ42, both indicators of reduced Aβ trimming activity (Liu et al., 2022; Apr 2022 news). Of note, in this study, Aβ37/Aβ42 outperformed Aβ42/Aβ40 as a biomarker for distinguishing between control and AD samples.

A cryo-electron microscopy study of the atomic structure of γ-secretase bound to an APP fragment indicates this residue appears to help stabilize the structural re-arrangement of PSEN1 upon APP binding (Zhou et al., 2019; Jan 2019 news). Moreover, several in silico algorithms (SIFT, Polyphen-2, LRT, MutationTaster, MutationAssessor, FATHMM, PROVEAN, CADD, REVEL, and Reve in the VarCards database) predicted this variant is damaging (Xiao et al., 2021). These authors classified the variant as likely pathogenic using the ACMG-AMP guidelines (Richards et al., 2015).

Pathogenicity

Alzheimer's Disease : Pathogenic

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

PS3-S

Well-established in vitro or in vivo functional studies supportive of a damaging effect on the gene or gene product.

PM1-S

Located in a mutational hot spot and/or critical and well-established functional domain (e.g. active site of an enzyme) without benign variation. P267A: Variant is in a mutational hot spot and cryo-EM data suggest residue is of functional importance.

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.

PM5-M

Novel missense change at an amino acid residue where a different missense change determined to be pathogenic has been seen before.

PP2-P

Missense variant in a gene that has a low rate of benign missense variation and where missense variants are a common mechanism of disease.

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: 29 Nov 2022

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References

News Citations

Paper Citations

Ringman JM, Monsell S, Ng DW, Zhou Y, Nguyen A, Coppola G, Van Berlo V, Mendez MF, Tung S, Weintraub S, Mesulam MM, Bigio EH, Gitelman DR, Fisher-Hubbard AO, Albin RL, Vinters HV. Neuropathology of Autosomal Dominant Alzheimer Disease in the National Alzheimer Coordinating Center Database. J Neuropathol Exp Neurol. 2016 Mar;75(3):284-90. Epub 2016 Feb 17 PubMed.
Liu L, Lauro BM, He A, Lee H, Bhattarai S, Wolfe MS, Bennett DA, Karch CM, Young-Pearse T, Dominantly Inherited Alzheimer Network (DIAN), Selkoe DJ. Identification of the Aβ37/42 peptide ratio in CSF as an improved Aβ biomarker for Alzheimer's disease. Alzheimers Dement. 2022 Mar 12; PubMed.
Zhou R, Yang G, Guo X, Zhou Q, Lei J, Shi Y. Recognition of the amyloid precursor protein by human γ-secretase. Science. 2019 Feb 15;363(6428) Epub 2019 Jan 10 PubMed.
Xiao X, Liu H, Liu X, Zhang W, Zhang S, Jiao B. APP, PSEN1, and PSEN2 Variants in Alzheimer's Disease: Systematic Re-evaluation According to ACMG Guidelines. Front Aging Neurosci. 2021;13:695808. Epub 2021 Jun 18 PubMed.
Richards S, Aziz N, Bale S, Bick D, Das S, Gastier-Foster J, Grody WW, Hegde M, Lyon E, Spector E, Voelkerding K, Rehm HL, ACMG Laboratory Quality Assurance Committee. Standards and guidelines for the interpretation of sequence variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology. Genet Med. 2015 May;17(5):405-24. Epub 2015 Mar 5 PubMed.

Mutations

PSEN1 P267A

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