SNCA and multiple system atrophy: To determine if MSA prions replicate in Tg mice expressing E46K α-synuclein in vivo, we inoculated eight-week-old TgM47+/- mice intracranially (i.c.)with 30 μL 1% brain homogenate prepared from either two control patient samples (C9 and C17) or three MSA patient samples (MSA5, MSA14, and MSA17; S2 Table) and monitored the mice for the onset of neurological signs (Fig 1).