PNKP and Ataxia: There are four subtypes of ataxia with oculomotor apraxia (AOA): AOA1 [mutations in APTX (Moreira et al., 2001) and/or PNKP (Bras et al., 2015)]; AOA2 [mutations in SETX (Airoldi et al., 2010)]; AOA3 [mutations in PIK3R5 (Tassan et al., 2012)]; AOA4 [mutations in PNKP (Paucar et al., 2016; Rudenskaya et al., 2019)].