Mutations

PSEN1 L271V

Overview

Pathogenicity: Alzheimer's Disease : Pathogenic
Clinical Phenotype: Alzheimer's Disease
Genomic Mutation Name (MET1): g.49996C>G
Genomic Mutation Name (NT1): g.66602C>G
dbSNP ID: rs63750886
Coding/Non-Coding: Coding
Genomic Region: Exon 8
Mutation Type: Point, Missense
Codon Change: CTG to GTG

Findings

This mutation was detected in a large pedigree (Tas-1) affected by early onset Alzheimer’s disease. The reported pedigree shows 13 affected individuals over three generations in a pattern consistent with autosomal-dominant inheritance. Presenting clinical features were typical of AD, starting with difficulties in activities of daily living followed by progressive deficits in memory, language, and visuo-spatial skills. Severe dementia typically developed over a span of several years. Myoclonus was a late feature, but spastic paraparesis was not observed. The onset of symptoms ranged from 43 years to the early 60s (mean: 49 years). The age at death ranged from 52 to 65 years, with one affected individual still living at 68 years at the time of the report.

DNA from 18 family members, including five affected individuals, was assessed. All affected individuals were mutation carriers, consistent with L271V conferring pathogenicity in this kindred (Kwok et al., 2003).

Neuropathology

Two affected members of the Tas-1 pedigree were examined neuropathologically. One died of pulmonary emboli at the age of 60, the other of bronchopneumonia at age 57. Macroscopically, both brains showed considerable atrophy of the temporal and posterior white matter with enlargement of the lateral ventricles. The locus coeruleus was depigmented in both cases. Microscopically, a large number of plaques were noted in the neocortex (CERAD rating: severe). Many of the plaques were a variant type: large, non-cored plaques without neuritic dystrophy, reminiscent of cotton-wool plaques (Kwok et al., 2003).

Biological Effect

This mutation affects splicing such that exon 8 is more frequently excluded from transcripts. It also results in an amino acid replacement (D257A) at the splice junction of exons 7 and 9. In Cos-7 cells, when co-expressed with mutant APP carrying the Swedish mutation, the L271V mutation increases levels of secreted Aβ1–42 compared with wild-type PSEN1 (Kwok et al., 2003). A similar increase in secreted Aβ1–42 was observed in HEK293 cells co-expressing wild-type APP (751) (Dumanchin et al., 2006); however, no effect on Aβ production has been reported (Morihara et al., 2000).

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References

Mutations Citations

  1. APP KM670/671NL (Swedish)

Paper Citations

  1. . Presenilin-1 mutation L271V results in altered exon 8 splicing and Alzheimer's disease with non-cored plaques and no neuritic dystrophy. J Biol Chem. 2003 Feb 28;278(9):6748-54. PubMed.
  2. . 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.
  3. . Absence of endoproteolysis but no effects on amyloid beta production by alternative splicing forms of presenilin-1, which lack exon 8 and replace D257A. Brain Res Mol Brain Res. 2000 Dec 28;85(1-2):85-90. PubMed.

Further Reading

Learn More

Alzheimer Disease & Frontotemporal Dementia Mutation Database

Primary Papers

  1. . Presenilin-1 mutation L271V results in altered exon 8 splicing and Alzheimer's disease with non-cored plaques and no neuritic dystrophy. J Biol Chem. 2003 Feb 28;278(9):6748-54. PubMed.