In the second research article, “Methyl-Arginine Profile of Brain from Aged PINK1-KO+A53T-SNCA Mice Suggests Altered Mitochondrial Biogenesis,” G. Auburger et al. use a powerful experimental model (PINK1-knockout with overexpression of A53T-SNCA double-mutant mice) to elucidate the polygenic etiology of PD. The gene discussed is PINK1; the disease is Parkinson disease.