Mutations

PSEN1 L134R

Overview

Pathogenicity: Alzheimer's Disease : Not Classified
ACMG/AMP Pathogenicity Criteria: PS3, PM1, PM2, PP2, PP3
Clinical Phenotype: Alzheimer's Disease
Position: (GRCh38/hg38):Chr14:73173628 T>G
Position: (GRCh37/hg19):Chr14:73640336 T>G
dbSNP ID: NA
Coding/Non-Coding: Coding
DNA Change: Substitution
Expected RNA Consequence: Substitution
Expected Protein Consequence: Missense
Codon Change: CTG to CGG
Reference Isoform: PSEN1 Isoform 1 (467 aa)
Genomic Region: Exon 5

Findings

This mutation was detected in a Turkish man with a family history of Alzheimer’s disease. The proband developed symptoms at age 53, starting with memory impairment. His disease progressed rapidly, and he developed mood lability, disorientation, visual hallucinations, and spasticity in his legs. He was bedridden by age 55 and died four years after onset.

At least four members of this family (AD-46) were affected by AD. Transmission was consistent with autosomal dominant inheritance; however, segregation with disease could not be determined due to lack of DNA from family members (Lohmann et al., 2012).

This variant is absent from the gnomAD variant database (gnomAD v2.1.1, May 2021).

Neuropathology

Neuropathological data are unavailable, but MRI of the Turkish proband showed atrophy of the cerebrum and cerebellum (Lohmann et al., 2012).

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 levels of toxic peptides Aβ42 and Aβ43. Moreover, the Aβ42/Aβ40 ratio was increased and the Aβ37/Aβ42 ratio was decreased, 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.

In contrast to these cell-based results, an in vitro assay using purified proteins to test the ability of this variant to cleave the APP-C99 substrate revealed decreased production of Aβ42, and no detectable production of Aβ40 (Sun et al., 2017). This may be due to deficient cleavage efficiency in this assay—68 of the 138 mutant 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). It has been classified as possibly pathogenic according to the algorithm proposed by Guerreiro et al., 2010 (Lohmann et al., 2012).

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.

PS3-S

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

PM1-P

Located in a mutational hot spot and/or critical and well-established functional domain (e.g. active site of an enzyme) without benign variation. L134R: Variant located at edge of mutational hot spot.

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.

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

Last Updated: 06 Mar 2024

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References

News Citations

  1. Ratio of Short to Long Aβ Peptides: Better Handle on Alzheimer's than Aβ42/40?

Paper Citations

  1. Lohmann E, Guerreiro RJ, Erginel-Unaltuna N, Gurunlian N, Bilgic B, Gurvit H, Hanagasi HA, Luu N, Emre M, Singleton A. Identification of PSEN1 and PSEN2 gene mutations and variants in Turkish dementia patients. Neurobiol Aging. 2012 Aug;33(8):1850.e17-27. PubMed.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  6. Guerreiro RJ, Baquero M, Blesa R, Boada M, Brás JM, Bullido MJ, Calado A, Crook R, Ferreira C, Frank A, Gómez-Isla T, Hernández I, Lleó A, Machado A, Martínez-Lage P, Masdeu J, Molina-Porcel L, Molinuevo JL, Pastor P, Pérez-Tur J, Relvas R, Oliveira CR, Ribeiro MH, Rogaeva E, Sa A, Samaranch L, Sánchez-Valle R, Santana I, Tàrraga L, Valdivieso F, Singleton A, Hardy J, Clarimón J. Genetic screening of Alzheimer's disease genes in Iberian and African samples yields novel mutations in presenilins and APP. Neurobiol Aging. 2010 May;31(5):725-31. Epub 2008 Jul 30 PubMed.

External Citations

  1. gnomAD v2.1.1

Further Reading

No Available Further Reading

Protein Diagram

Primary Papers

  1. Lohmann E, Guerreiro RJ, Erginel-Unaltuna N, Gurunlian N, Bilgic B, Gurvit H, Hanagasi HA, Luu N, Emre M, Singleton A. Identification of PSEN1 and PSEN2 gene mutations and variants in Turkish dementia patients. Neurobiol Aging. 2012 Aug;33(8):1850.e17-27. PubMed.

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