title: Somatic and germline mosaicism in sporadic early-onset Alzheimer's disease.
abstract: Alzheimer's disease (AD) is the commonest neurodegenerative disease worldwide. Rare familial cases may be caused by mutations in one of three genes-amyloid precursor protein, presenilin-1 and presenilin-2; however, the molecular basis of >99% of AD cases is unknown. Somatic mutation has been considered to be a mechanism that may account for a proportion of sporadic cases of AD, but to date there has been no evidence for this. We now report a sporadic early-onset patient with AD, and show that this individual is a somatic mosaic for a mutation in the presenilin-1 gene, suggesting a novel molecular mechanism for AD. Quantification of the mosaicism demonstrated the degree of mosaicism at 8% in peripheral lymphocytes and 14% in cerebral cortex in the index patient; a clear gene dosage effect on age of presentation and clinical phenotypic presentation is demonstrated. This finding has important implications for the aetiology of sporadic AD, and for other apparently sporadic neurodegenerative diseases such as Parkinson's disease, motor neuron disease and Creutzfeldt-Jakob disease.
authors.affiliation: MRC Prion Unit and Department of Neurodegenerative Disease, Institute of Neurology UCL, Queen Square, London, UK.
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Beck
authors.forename: Mark
authors.initials: M
authors.lastname: Poulter
authors.forename: Tracy A
authors.initials: TA
authors.lastname: Campbell
authors.forename: James B
authors.initials: JB
authors.lastname: Uphill
authors.forename: Gary
authors.initials: G
authors.lastname: Adamson
authors.forename: Jennian F
authors.initials: JF
authors.lastname: Geddes
authors.forename: Tamas
authors.initials: T
authors.lastname: Revesz
authors.forename: Mary B
authors.initials: MB
authors.lastname: Davis
authors.forename: Nicholas W
authors.initials: NW
authors.lastname: Wood
authors.forename: John
authors.initials: J
authors.lastname: Collinge
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Tabrizi
mesh_terms: D000328:Adult; D017668:Age of Onset; D000544:Alzheimer Disease / Q000235:genetics*; D001483:Base Sequence; D005260:Female; D018095:Germ-Line Mutation / Q000235:genetics*; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D008875:Middle Aged; D009030:Mosaicism; D010375:Pedigree; D053764:Presenilin-1
chemical_list: D008565:Membrane Proteins; C508853:PSEN1 protein, human; D053764:Presenilin-1