Extended Data Fig. 8: Proposed Model for AraC-induced cerebellar toxicity.

In Purkinje cells (PCs) of the cerebellum, a subset of highly expressed genes essential for motor coordination (Itpr1, Grid2 and etc.) undergoes active DNA demethylation. These genes are extensively covered with broad H3K27ac domains associated with enhancer marks. Active DNA demethylation involves TET-mediated oxidation of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxycytosine (5caC), followed by TDG-mediated excision of 5fC/5caC. AraC can interrupt base excision repair leading to double-strand breaks (DSBs) within gene bodies. AraC-induced DSBs can directly decrease gene expression or be processed into insertion/deletions (indels) and translocations, which can contribute to the development of cerebellar ataxia.