These results highlight several factors that complicate the follow-up of associated variants at the LRRK2 locus in all diseases and in particular PD: the existence of multiple LRRK2 isoforms, variability in mRNA expression and splicing across brain regions, and localisation of LRRK2 protein to both neuronal and non-neuronal cell types. The gene discussed is LRRK2; the disease is Parkinson disease.