Overview

Pathogenicity: Alzheimer's Disease : Pathogenic
ACMG/AMP Pathogenicity Criteria: PS3, PM1, PM2, PP2, PP3, PS4
Clinical Phenotype: Alzheimer's Disease
Reference Assembly: GRCh37/hg19
Position: Chr14:73653592 T>C
dbSNP ID: rs63750963
Coding/Non-Coding: Coding
DNA Change: Substitution
Expected RNA Consequence: Substitution
Expected Protein Consequence: Missense
Codon Change: CTA to CCA
Reference Isoform: PSEN1 Isoform 1 (467 aa)
Genomic Region: Exon 6

Findings

This mutation was found in a Mexican family with early onset AD (Ramirez-Duenas et al., 1998). It was also found in a study of British AD patients with at least one affected first-degree relative, and an age of onset of less than 61 years (Janssen et al., 2003). The family of this proband had three affected members spanning three generations, with a mean age at onset of 38 years. Another British family was reported with five affected members, with a mean age at onset of 42 (Ryan et al., 2016).

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

Biological Effect

Two in-depth studies of the Aβ peptides produced by cells transfected with this variant revealed a deleterious effect, decreasing both the Aβ (37 + 38 + 40) / (42 + 43) and Aβ37/Aβ42 ratios compared with cells expressing wildtype PSEN1 (Apr 2022 news; Petit et al., 2022; Liu et al., 2022). Both ratios were reported to outperform the Aβ42/Aβ40 ratio as indicators of AD pathogenicity, with the former correlating with AD age at onset.

In an in vitro assay with isolated proteins, this mutant produced less Aβ42 than wild-type PSEN1, and Aβ40 production was undetectable (Sun et al., 2017). However, this assay appears to be limited in its cleavage efficiency given that 68 of 138 mutant recombinant PSEN1 enzymes tested produced less than 10 percent of the Aβ40 and Aβ42 produced by the wildtype protein (Liu et al., 2021).

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).

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-M

Located in a mutational hot spot and/or critical and well-established functional domain (e.g. active site of an enzyme) without benign variation.

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.

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.

PS4-M

The prevalence of the variant in affected individuals is significantly increased compared to the prevalence in controls. L171P: The variant was reported in 3 or more unrelated patients with the same phenotype, and absent from controls.

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

Last Updated: 10 Nov 2022

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References

News Citations

Paper Citations

Ramirez-Dueñas MG, Rogaeva EA, Leal CA, Lin C, Ramirez-Casillas GA, Hernandez-Romo JA, St George-Hyslop PH, Cantu JM. A novel Leu171Pro mutation in presenilin-1 gene in a Mexican family with early onset Alzheimer disease. Ann Genet. 1998;41(3):149-53. PubMed.
Janssen JC, Beck JA, Campbell TA, Dickinson A, Fox NC, Harvey RJ, Houlden H, Rossor MN, Collinge J. Early onset familial Alzheimer's disease: Mutation frequency in 31 families. Neurology. 2003 Jan 28;60(2):235-9. PubMed.
Ryan NS, Nicholas JM, Weston PS, Liang Y, Lashley T, Guerreiro R, Adamson G, Kenny J, Beck J, Chavez-Gutierrez L, de Strooper B, Revesz T, Holton J, Mead S, Rossor MN, Fox NC. Clinical phenotype and genetic associations in autosomal dominant familial Alzheimer's disease: a case series. Lancet Neurol. 2016 Dec;15(13):1326-1335. Epub 2016 Oct 21 PubMed.
Petit D, Fernández SG, Zoltowska KM, Enzlein T, Ryan NS, O'Connor A, Szaruga M, Hill E, Vandenberghe R, Fox NC, Chávez-Gutiérrez L. Aβ profiles generated by Alzheimer's disease causing PSEN1 variants determine the pathogenicity of the mutation and predict age at disease onset. Mol Psychiatry. 2022 Jun;27(6):2821-2832. Epub 2022 Apr 1 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.
Sun L, Zhou R, Yang G, Shi Y. Analysis of 138 pathogenic mutations in presenilin-1 on the in vitro production of Aβ42 and Aβ40 peptides by γ-secretase. Proc Natl Acad Sci U S A. 2017 Jan 24;114(4):E476-E485. Epub 2016 Dec 5 PubMed.
Liu L, Lauro BM, Wolfe MS, Selkoe DJ. Hydrophilic loop 1 of Presenilin-1 and the APP GxxxG transmembrane motif regulate γ-secretase function in generating Alzheimer-causing Aβ peptides. J Biol Chem. 2021;296:100393. Epub 2021 Feb 8 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.

Mutations

PSEN1 L171P

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