HIP1R and Parkinson disease: Interestingly, AGTR1, a gene associated with many PD single-nuclei subpopulations included in our model, encodes for angiotensin II receptor type 1 protein.58 This protein is part of the renin-angiotensin system, which regulates blood pressure and the balance of fluids and salts in the body.58 Ho et al. 57 also validated some of the top genes from our model such as INPP5F, P2RY12, HIP1R, STK39 and CTSB.