IDH2 and astrocytoma (excluding glioblastoma): Conversely, the absence of TERT promoter mutations combined with the presence of IDH mutations is indicative of astrocytoma [9-12].The ATRX gene encodes the ATRX protein, a transcriptional regulator with two functional domains: the zinc finger domain, which acts as a transcription factor, and the helicase domain, which facilitates the unwinding of double-stranded DNA during transcription.