SPINK1 and cyst: Of note, as observed for the TgISU1 mutant and parental TATi ΔKu80 cell line, these other mutants generated in a type I background strain also displayed smaller cyst size than the type II parasites after long term induction of stage conversion (S11C Fig), suggesting reactivation may happen and incomplete differentiation is likely a general feature of RH-derived parasites.