TDP1 and axonal neuropathy: Accordingly, genetic inactivation of TDP1 causes hypersensitivity to CPT, while homozygous mutation of TDP1 causes the neurodegenerative syndrome, spinocerebellar ataxia with axonal neuropathy (SCAN1) resulting from elevated levels of Top1cc in post-mitotic neurons (Das et al, 2010; Huang et al, 2013; Interthal et al, 2005; Interthal et al, 2001; Katyal et al, 2007; Murai et al, 2012; Pommier et al, 2014; Takashima et al, 2002; Vance and Wilson, 2002).