CHRNA7 and Parkinson disease: Our previous studies found that α7nAChRs may mediate the protective effects of nicotine in vivo in PD model mice (Liu et al., 2015, 2017) and in vitro in cultured 1-methyl-4-phenylpyridinium (MPP+)-induced SH-SY5Y cells (Xu et al., 2019).