IDH1 and astrocytoma (excluding glioblastoma): To explore the potential role of different mutation types in the formation of astrocytomas and oligodendroglial tumors, we determined the enzyme kinetics of wild type IDH1 and with the mutations R132H, R132C, R132G, R132S, R132L and R100Q followed by quantification of 2-HG in transfected cells and in human tumor tissues, and examined the effects on viability.