The APOE ε2 allele may decrease the age at onset in patients with spinocerebellar ataxia type 3 or Machado-Joseph disease from the Chinese Han population

Polymorphism of the apolipoprotein E (APOE) gene has been defined as a modifying factor for age at onset (AO) in neurodegenerative disorders. The AO of spinocerebellar ataxia type 3 or Machado-Joseph disease (SCA3 or MJD) is inversely correlated with expanded CAG repeat lengths in the ATXN3 gene; however, AO is only partially explained by the expanded CAG repeats. We performed a case-control study to explore whether APOE genotypes play a role in AO of SCA3 or MJD from the Chinese Han population. The APOE genotypes were analyzed in an independent cohort of 155 patients with SCA3 or MJD and 191 controls both from Mainland China. Our study demonstrated that SCA3 or MJD patients experienced an earlier onset if they were carriers of APOE ε2 allele, which decreased the AO by nearly 4 years. This study may also reconfirm the effect of the APOE gene on SCA3 or MJD patients from different races and indicated that certain APOE alleles might be genetic modifiers for AO in SCA3 or MJD.