title: Asian origin for the worldwide-spread mutational event in Machado-Joseph disease.
abstract: BACKGROUND
  Machado-Joseph disease is the most frequent dominant ataxia worldwide. Despite its frequency and presence in many populations, only 2 founder mutations have been suggested to explain its current geographic distribution.
  
  
  OBJECTIVE
  To trace back in history the main mutational events in Machado-Joseph disease, we aimed to assess ancestral haplotypes and population backgrounds, to date the mutations, and to trace the routes and time of introduction of the founder haplotypes in different populations.
  
  
  METHODS
  We studied 264 families with Machado-Joseph disease from 20 different populations. Six intragenic single-nucleotide polymorphisms were used to determine ancestral mutational events; 4 flanking short tandem repeats were used to construct extended haplotypes and measure accumulation of genetic diversity over time within each lineage.
  
  
  RESULTS
  The worldwide-spread lineage, TTACAC, had its highest diversity in the Japanese population, where we identified the ancestral short tandem repeat-based haplotype. Accumulated variability suggested a postneolithic mutation, about 5774 +/- 1116 years old, with more recent introductions in North America, Germany, France, Portugal, and Brazil. As to the second mutational event, in the GTGGCA lineage, only 7 families (of 71 families) did not have Portuguese ancestry, although gene diversity was again smaller in Portuguese families (0.44) than in non-Portuguese families (0.93).
  
  
  CONCLUSIONS
  The worldwide-spread mutation may have first occurred in Asia and later been diffused throughout Europe, with a founder effect accounting for its high prevalence in Portugal; the other Machado-Joseph disease lineage is more recent, about 1416 +/- 434 years old, and its dispersion may be explained mainly by recent Portuguese emigration.
authors.affiliation: Instituto de Patologia e Imunologia Molecular da Universidade do Porto and Faculdade de Ciências, University of Porto, Porto, Portugal.
authors.forename: Sandra
authors.initials: S
authors.lastname: Martins
authors.forename: Francesc
authors.initials: F
authors.lastname: Calafell
authors.forename: Claudia
authors.initials: C
authors.lastname: Gaspar
authors.forename: Virginia C N
authors.initials: VC
authors.lastname: Wong
authors.forename: Isabel
authors.initials: I
authors.lastname: Silveira
authors.forename: Garth A
authors.initials: GA
authors.lastname: Nicholson
authors.forename: Ewout R
authors.initials: ER
authors.lastname: Brunt
authors.forename: Lisbeth
authors.initials: L
authors.lastname: Tranebjaerg
authors.forename: Giovanni
authors.initials: G
authors.lastname: Stevanin
authors.forename: Mingli
authors.initials: M
authors.lastname: Hsieh
authors.forename: Bing-Wen
authors.initials: BW
authors.lastname: Soong
authors.forename: Leal
authors.initials: L
authors.lastname: Loureiro
authors.forename: Alexandra
authors.initials: A
authors.lastname: Dürr
authors.forename: Shoji
authors.initials: S
authors.lastname: Tsuji
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Watanabe
authors.forename: Laura B
authors.initials: LB
authors.lastname: Jardim
authors.forename: Paola
authors.initials: P
authors.lastname: Giunti
authors.forename: Olaf
authors.initials: O
authors.lastname: Riess
authors.forename: Laura P W
authors.initials: LP
authors.lastname: Ranum
authors.forename: Alexis
authors.initials: A
authors.lastname: Brice
authors.forename: Guy A
authors.initials: GA
authors.lastname: Rouleau
authors.forename: Paula
authors.initials: P
authors.lastname: Coutinho
authors.forename: António
authors.initials: A
authors.lastname: Amorim
authors.forename: Jorge
authors.initials: J
authors.lastname: Sequeiros
mesh_terms: D001208:Asia / Q000453:epidemiology; D004641:Emigration and Immigration; D005060:Europe / Q000453:epidemiology; D018703:Founder Effect; D006239:Haplotypes; D006801:Humans; D007564:Japan / Q000453:epidemiology; D017827:Machado-Joseph Disease / Q000453:epidemiology* / Q000235:genetics*; D009154:Mutation / Q000502:physiology*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D011153:Population; D011174:Portugal / Q000453:epidemiology; D020080:Tandem Repeat Sequences / Q000235:genetics