ATRX and astrocytoma (excluding glioblastoma): A realistic model of IDH‐mutant astrocytomas (characterised by IDH, ATRX, and p53 mutations, and in grade 4 astrocytomas frequent additional deletion of CDKN2A/B) was accomplished by combining IDH (R132H) expression, and Atrx and p53 inactivation using the sleeping beauty technology.