Further studies examining the LRRK2 expression in different neuronal subtypes in the colon, such as choline acetyltransferase (ChAT)-positive, vasoactive intestinal peptide (VIP)-secreting neurons and sympathetic tyrosine hydroxylase-positive neurons, will provide a more comprehensive landscape of LRRK2 expression in individual cell types of PD process. The gene discussed is TH; the disease is Parkinson disease.