A genome-wide linkage screen in the Amish with Parkinson disease points to chromosome 6.

Parkinson disease (PD) is a common complex neurodegenerative disorder with an underlying genetic etiology that has been difficult to dissect. Although some PD risk genes have been discovered, most of the underlying genetic etiology remains unknown. To further elucidate the genetic component, we have undertaken a genome-wide linkage screen in an isolated founder population of Amish living in the Midwestern United States. We performed tests for linkage and for association using a marker set of nearly 6000 single-nucleotide polymorphisms. Parametric multipoint linkage analysis generated a logarithm of the odds of linkage (LOD) score of 2.44 on chromosome 6 in the SYNE1 gene, approximately 8 Mbp from the PARK2 gene. In a different region on chromosome 6 (∼67 Mbp from PARK2) an association was found for rs4302647 (p < 4.0 × 10(-6) ), which is not within 300 kb of any gene. While the association exceeds Bonferroni correction, it may yet represent a false positive due to the small sample size and the low minor allele frequency. The minor allele frequency in affecteds is 0.07 compared to 0.01 in unaffecteds. Taken together, these results support involvement of loci on chromosome 6 in the genetic etiology of PD.