Mutations

PSEN1 F105I

Overview

Pathogenicity: Alzheimer's Disease : Likely Pathogenic
Clinical Phenotype: Alzheimer's Disease
Reference Assembly: GRCh37/hg19
Position: Chr14:73637730 T>A
dbSNP ID: rs63750325
Coding/Non-Coding: Coding
Mutation Type: Point, Missense
Codon Change: TTT to ATT
Reference Isoform: PSEN1 Isoform 1 (467 aa)
Genomic Region: Exon 4

Findings

This mutation was identified in a family known as Alz 184. The three reported affected members of this family met NINCDS-ADRDA criteria for probable or definite Alzheimer’s disease. The age at onset ranged from 53 to 58 years (Raux et al., 2005).

The variant was also found in a Chinese family with six affected individuals spanning four generations (Jia et al., 2020). Four of the affected members carried the variant and were diagnosed with AD. Mean age at onset was 48 years. Two carriers had APOE E3/E4 genotypes and two had APOE E3/3 genotypes.

The variant was absent from the gnomAD variant database (gnomAD v2.1.1, May 2021).

Neuropathology

Unknown.

Biological Effect

This mutant appears to reduce γ-processivity (Liu et al., 2021). Analysis of secreted Aβs in the conditioned media of human embryonic kidney cells lacking endogenous PSENs and expressing this mutant along with wildtype APP, revealed increased Aβ42/40 ratio and decreased Aβ37/40, Aβ37/42, and Aβ38/42 ratios. Interestingly, the authors also reported that Aβ42/40, Aβ38/42, and particularly Aβ37/42, ratios each correlated with reported ages of onset of clinical impairment across 16 PSEN1 mutations. This mutant also reduced total secreted Aβ levels. Consistently, an in vitro assay using purified proteins to test the ability of this mutant to cleave the APP-C99 substrate revealed decreased Aβ42, and particularly Aβ40, production resulting in a nearly 10-fold increase in the Aβ42/Aβ40 ratio (Sun et al., 2017).

Five out of five in silico algorithms (Polyphen2, PANTHER, Mutpred2, PROVEAN , and Mutation Taster) predicted this substitution to be damaging (Jia et al., 2020) with a PHRED-CADD score of 27.7. However, another study, including a different set of algorithms (SIFT, Polyphen-2, LRT, MutationTaster, MutationAssessor, FATHMM, PROVEAN, CADD, REVEL, and Reve in the VarCards database), reported conflicting results (Xiao et al., 2021).

Last Updated: 28 Aug 2021

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References

Paper Citations

  1. . Molecular diagnosis of autosomal dominant early onset Alzheimer's disease: an update. J Med Genet. 2005 Oct;42(10):793-5. Epub 2005 Jul 20 PubMed.
  2. . PSEN1, PSEN2, and APP mutations in 404 Chinese pedigrees with familial Alzheimer's disease. Alzheimers Dement. 2020 Jan;16(1):178-191. PubMed.
  3. . 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 Jan-Jun;296:100393. Epub 2021 Feb 8 PubMed.
  4. . 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.
  5. . 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.

External Citations

  1. gnomAD v2.1.1

Further Reading

No Available Further Reading

Protein Diagram

Primary Papers

  1. . Molecular diagnosis of autosomal dominant early onset Alzheimer's disease: an update. J Med Genet. 2005 Oct;42(10):793-5. Epub 2005 Jul 20 PubMed.

Other mutations at this position

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