Mutations

PSEN1 P264L

Overview

Pathogenicity: Alzheimer's Disease : Pathogenic
Clinical Phenotype: Alzheimer's Disease, Atypical Dementia, Progressive Nonfluent Aphasia, Spastic Paraparesis
Genomic Mutation Name (MET1): g.49976C>T
Genomic Mutation Name (NT1): g.66582C>T
dbSNP ID: rs63750301
Coding/Non-Coding: Coding
Genomic Region: Exon 8
Mutation Type: Point, Missense
Codon Change: CCG to CTG
Research Models: 1

Findings

This mutation has been detected in at least 13 families worldwide, with a variable, and often atypical, presentation of Alzheimer’s disease. The diversity of phenotypic expression associated with this mutation is unusual and includes spastic paraparesis, dementia with Lewy bodies, atypical dementia, lobar hemorrhage, and non-fluent primary progressive aphasia.

The P264L mutation was first reported in 1995 in a French kindred known as SAL 511. As reported, the family contained six affected individuals with age of onset ranging from 45 to 56. The mutation was shown to segregate with disease (Campion et al., 1995). Affected family members were diagnosed with AD according to NINCDS-ADRDA criteria, but they also frequently presented with atypical features such as myoclonus, extrapyramidal signs, and seizures. Neuropathological examination revealed plaque and tangle pathology consistent with a diagnosis of AD in at least two family members (Campion et al., 1995). This family was also analyzed in Campion et al., 1999, along with two other French families known as SAL 506 and SAL 1633, both with four affected individuals in three generations. Ages of onset in these families were 46 to 52 and 51 to 55 years, respectively. The clinical presentation in the SAL 1633 family was notable for a spastic paraparesis phenotype. At least three additional French families have been identified, and are also reported to be commonly affected by spastic paraparesis (Raux et al., 2005; Jacquemont et al., 2002; Dumanchin et al., 2006).

Several additional families with this mutation have been reported. One pedigree, known as MGH6, consisted of two affected individuals with onset at ages 45 and 50 years, one with autopsy-confirmed AD (Wasco et al., 1995). A pedigree known as EOFAD-6 had a mean age of onset of 39 years and autopsy-confirmed AD (Kwok et al., 1997). A British kindred known as KG has been reported with five reported affected individuals, three with autopsy-confirmed AD, and an overall age of onset ranging from 41 to 45 years (Poorkaj et al., 1998). Similar to the previously reported French families, an additional P264L kindred of unspecified origins had at least one family member affected by spastic paraparesis. Another member in this family met clinical criteria for dementia with Lewy bodies, while another displayed symptoms more typical of AD (Martikainen et al., 2010).

More recently, a Turkish family known as DEM-9 was found to carry this mutation. The proband in this family developed memory problems and personality changes at the age of 51; her mother reportedly had been affected at age 60. The proband's brother, who also carried the mutation, did not report subjective memory difficulties at the age of 51, although significant impairments were noted by specialized neuropsychological tests. He had a university degree and worked as an engineer, suggesting that cognitive reserve may have delayed functional impairment in this case (Lohmann et al., 2012).

Further highlighting the variability of this mutation even within a family, two Japanese siblings carrying the P264L mutation presented with different phenotypes, one with atypical AD with features of frontotemporal dementia, and the other with typical AD based on clinical symptoms and brain imaging (Ishizuka et al., 2012).

Finally, the occurrence of non-fluent primary progressive asphasia in one mutation carrier from the United Kingdom rounds out the clinical heterogeneity associated with P264L. The patient presented at age 45 with a three-year history of progressive speech and word-finding difficulties. Her father had developed cognitive decline around age 60 with insidious behavioral changes and episodic memory difficulties. As he was predeceased, it is unknown if he carried the mutation (Mahoney et al., 2013).

Neuropathology

Like the clinical presentation associated with this mutation, the associated neuropathology is variable. One patient had significant white-matter abnormalities. Another suffered a right occipital hemorrhage four years after dementia onset. In a third, neuropathology was consistent with a diagnosis of AD (Braak stage VI), but also included severe cerebral amyloid angiopathy with numerous small infarcts in the cortex (Dumanchin et al., 2006). Detailed neuropathology for three affected mutation carriers within a single family has been described (Martikainen et al., 2010). In brief, the authors observed abundant cotton-wool plaques composed of Aβ42 but also containing hyperphosphorylated tau, and in one case TDP-43. The distribution of the pathology varied, but associations were observed between neocortical/thalamic involvement and psychiatric symptoms, between striatal/amygdaloid involvement and Parkinsonism, and between brain-stem involvement and spastic paraparesis.

Biological Effect

In vitro, the P264L mutation did not affect exon 9 splicing and had only a small, non-significant effect on the Aβ42/Aβ40 ratio (Dumanchin et al., 2006). When expressed in COS-1 cells co-transfected with APP695, this mutation resulted in a small increase in the Aβ42/Aβ total ratio (Murayama et al., 1999). This mutation is predicted probably damaging in silico with PolyPhen-2 and is predicted to have definite pathogenicity according to the algorithm proposed by Guerreiro et al., 2010 (Lohmann et al., 2012).

Research Models

This mutation has been introduced into mouse models of disease, for example, see PS1 P264L.

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References

Paper Citations

  1. . Mutations of the presenilin I gene in families with early-onset Alzheimer's disease. Hum Mol Genet. 1995 Dec;4(12):2373-7. PubMed.
  2. . A large pedigree with early-onset Alzheimer's disease: clinical, neuropathologic, and genetic characterization. Neurology. 1995 Jan;45(1):80-5. PubMed.
  3. . Early-onset autosomal dominant Alzheimer disease: prevalence, genetic heterogeneity, and mutation spectrum. Am J Hum Genet. 1999 Sep;65(3):664-70. PubMed.
  4. . 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.
  5. . Spastic paraparesis and atypical dementia caused by PSEN1 mutation (P264L), responsible for Alzheimer's disease. J Med Genet. 2002 Feb;39(2):E2. PubMed.
  6. . Biological effects of four PSEN1 gene mutations causing Alzheimer disease with spastic paraparesis and cotton wool plaques. Hum Mutat. 2006 Oct;27(10):1063. PubMed.
  7. . Familial Alzheimer's chromosome 14 mutations. Nat Med. 1995 Sep;1(9):848. PubMed.
  8. . Two novel (M233T and R278T) presenilin-1 mutations in early-onset Alzheimer's disease pedigrees and preliminary evidence for association of presenilin-1 mutations with a novel phenotype. Neuroreport. 1997 Apr 14;8(6):1537-42. PubMed.
  9. . Missense mutations in the chromosome 14 familial Alzheimer's disease presenilin 1 gene. Hum Mutat. 1998;11(3):216-21. PubMed.
  10. . Brain pathology in three subjects from the same pedigree with presenilin-1 (PSEN1) P264L mutation. Neuropathol Appl Neurobiol. 2010 Feb;36(1):41-54. Epub 2009 Oct 22 PubMed.
  11. . Identification of PSEN1 and PSEN2 gene mutations and variants in Turkish dementia patients. Neurobiol Aging. 2012 Aug;33(8):1850.e17-27. PubMed.
  12. . Different Clinical Phenotypes in Siblings with a Presenilin-1 P264L Mutation. Dement Geriatr Cogn Disord. 2012;33(2-3):132-40. PubMed.
  13. . The Presenilin 1 P264L Mutation Presenting as non-Fluent/Agrammatic Primary Progressive Aphasia. J Alzheimers Dis. 2013 Jan 1;36(2):239-43. PubMed.
  14. . Enhancement of amyloid beta 42 secretion by 28 different presenilin 1 mutations of familial Alzheimer's disease. Neurosci Lett. 1999 Apr 9;265(1):61-3. PubMed.
  15. . 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.

Other Citations

  1. PS1 P264L

Further Reading

Learn More

Alzheimer Disease & Frontotemporal Dementia Mutation Database

Primary Papers

  1. . Mutations of the presenilin I gene in families with early-onset Alzheimer's disease. Hum Mol Genet. 1995 Dec;4(12):2373-7. PubMed.
  2. . Familial Alzheimer's chromosome 14 mutations. Nat Med. 1995 Sep;1(9):848. PubMed.