Mutations

PSEN1 M146L (A>T)

Overview

Pathogenicity: Alzheimer's Disease : Pathogenic
Clinical Phenotype: Alzheimer's Disease
Reference Assembly: GRCh37 (105)
Position: Chr14:73640371 A>T
dbSNP ID: rs63750306
Coding/Non-Coding: Coding
Mutation Type: Point, Missense
Codon Change: ATG to TTG
Reference Isoform: PSEN1 isoform 1 (467 aa)
Genomic Region: Exon 5

Findings

This mutation was identified in a South American pedigree from Argentina spanning five generations and including more than 110 individuals (Mangone et al., 1995; Morelli et al., 1998). Prominent features included mood changes, early language impairment, myoclonus, seizures, and cerebellar alterations. The mean age at onset was 39 years of age, but significant differences in this age were observed, especially between generations.

The most frequent alteration resulting in the M146L mutation appears to be an A>C transversion, M146L (A>C), but as exemplified by this family, an A>T transversion is also possible.

Neuropathology
Neuropathology is consistent with AD. In addition, SPECT imaging revealed bilateral frontal, temporo-parietal, and cerebellar hypoperfusion in early stage patients, and in an asymptomatic individual at risk.

Biological Effect
The summary below focuses on the M146L mutation, regardless of its underlying nucleotide change which, in some cases, is not reported.

In vitro, the M146L mutation has been found to increase Aβ42 and Aβ40 levels, as well as the Aβ42/Aβ40 and Aβ42/Aβ total ratios (Page et al., 2008; Sato et al., 2003; Shioi et al., 2007; Sun et al., 2017). Consistent with these findings, Aβ42 levels and the Aβ42/Aβ40 ratio were increased in conditioned media from M146L mutant fibroblasts and iPSC-derived neurons. No significant changes were observed in Aβ38 or Aβ40 levels (Liu et al., 2014). A cryo-electron microscopy study of the atomic structure of γ-secretase bound to an APP fragment indicates that, in wild-type PSEN1, M146 closely contacts the APP transmembrane helix, with its side-chain reaching towards the interior of the substrate-binding pore (Zhou et al., 2019; Jan 2019 news).

The M146L mutation also cleaves the calcium sensor STIM1 more efficiently than wild-type PSEN1 in vitro. This appears to impair calcium influx via STIM1 degradation and reduces spine density in cultured cells (Sep 2016 news; Tong et al., 2016). The mutation has also been reported to enhance gating of the IP3 receptor channel and increase the open probability of the mitochondrial permeability transition pore (Toglia and Ullah, 2016).

Last Updated: 03 Aug 2019

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References

Mutations Citations

  1. PSEN1 M146L (A>C)

News Citations

  1. CryoEM γ-Secretase Structures Nail APP, Notch Binding
  2. Mutant Presenilin Skews Calcium Homeostasis by Chomping on ER Sensor

Paper Citations

  1. . Early onset Alzheimer's disease in a South American pedigree from Argentina. Acta Neurol Scand. 1995 Jan;91(1):6-13. PubMed.
  2. . Presenilin 1 Met146Leu variant due to an A --> T transversion in an early-onset familial Alzheimer's disease pedigree from Argentina. Clin Genet. 1998 Jun;53(6):469-73. PubMed.
  3. . Generation of Abeta38 and Abeta42 is independently and differentially affected by familial Alzheimer disease-associated presenilin mutations and gamma-secretase modulation. J Biol Chem. 2008 Jan 11;283(2):677-83. PubMed.
  4. . Potential link between amyloid beta-protein 42 and C-terminal fragment gamma 49-99 of beta-amyloid precursor protein. J Biol Chem. 2003 Jul 4;278(27):24294-301. PubMed.
  5. . FAD mutants unable to increase neurotoxic Abeta 42 suggest that mutation effects on neurodegeneration may be independent of effects on Abeta. J Neurochem. 2007 May;101(3):674-81. Epub 2007 Jan 24 PubMed.
  6. . 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.
  7. . Effect of potent γ-secretase modulator in human neurons derived from multiple presenilin 1-induced pluripotent stem cell mutant carriers. JAMA Neurol. 2014 Dec;71(12):1481-9. PubMed.
  8. . Recognition of the amyloid precursor protein by human γ-secretase. Science. 2019 Feb 15;363(6428) Epub 2019 Jan 10 PubMed.
  9. . Familial Alzheimer's disease-associated presenilin 1 mutants promote γ-secretase cleavage of STIM1 to impair store-operated Ca2+ entry. Sci Signal. 2016 Sep 6;9(444):ra89. PubMed.
  10. . The gain-of-function enhancement of IP3-receptor channel gating by familial Alzheimer's disease-linked presenilin mutants increases the open probability of mitochondrial permeability transition pore. Cell Calcium. 2016 Jul;60(1):13-24. Epub 2016 May 7 PubMed.

Further Reading

Papers

  1. . Screening for PS1 mutations in a referral-based series of AD cases: 21 novel mutations. Neurology. 2001 Aug 28;57(4):621-5. PubMed.

Learn More

  1. Alzheimer Disease & Frontotemporal Dementia Mutation Database

Protein Diagram

Primary Papers

  1. . Early onset Alzheimer's disease in a South American pedigree from Argentina. Acta Neurol Scand. 1995 Jan;91(1):6-13. PubMed.
  2. . Presenilin 1 Met146Leu variant due to an A --> T transversion in an early-onset familial Alzheimer's disease pedigree from Argentina. Clin Genet. 1998 Jun;53(6):469-73. PubMed.

Other mutations at this position

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