Furthermore, variants within the LRRK2 and Rab29 genes synergistically increase Parkinson's risk [69], and studies in Caenorhabditis elegans indicated that RAB29 (GLO-1) ortholog acts upstream of LRRK2 (LRK-1) in a pathway controlling axon termination [73]. This evidence concerns the gene LRRK2 and Parkinson disease.