Project Summary/Abstract Gliomas are incurable and are the number two cause for tumor mortality in adult under 40 years old. Monoallelic mutations of IDH1 and IDH2, which encode isocitrate dehydrogenases (IDH) that convert isocitrate into α-ketoglutarate (αKG), have been detected in 80% of low grade gliomas (LGG) and nearly all secondary glioblastoma multiform (GBM). However, because IDH mutation-bearing glioma cells are difficult to isolate and propagate, an experimental system that allows dissection of the roles of IDH mutations and the subsequent genetic events in gliomagenesis is currently unavailable. Our overall goal is to understand the molecular mechanism underlying gliomagenesis and to identify novel targets to treat gliomas. It is generally believed that gliomas are originated from brain progenitor cells such as neural progenitor cells (NPCs). However, these cells are inaccessible for experimentation. Human pluripotent stem cells (hPSCs), such as human embryonic stem cells and induced pluripotent stem cells (iPSCs), have the potential to differentiate into different somatic cell types and organoids including brain organoid. Brain organoids possess primitive brain structure with different cell types and therefore may provide a microenvironment permissive for gliomagenesis. We hypothesize that iPSCs derived brain organoids serve as an alternative source for human brain cells, which can be used to dissect the roles of IDH mutations and other associated genetic events in LGGs. The objective of this proposal is to establish a novel brain organoid model for LGGs allowing assess the roles of IDH1 mutations and other glioma-associated genetic alterations in disease-relevant cell types. The rationale is that by establishing such a LGG model, we will be able to dissect the underlying molecular mechanism of gliomagenesis. These discoveries will ultimately facilitate identification of novel therapeutic targets and strengthen our capacity for therapeutic intervention. To achieve the objective, three specific aims are proposed. In Aim 1, we will assess the roles of IDH and TP53 mutations in gliomagenesis using the brain organoid LGG model. We will first generate brain organoid from iPSCs and then introduce genetic changes including IDH1 mutation and TP53 knock-down. In Aim 2, we will assess the role of ATRX mutation in brain organoid based gliomagenesis in vitro. In Aim 3. We will characterize brain organoid-derived xenograft tumor in comparison to genetically engineered brain organoids and patient LGGs. If successfully completed, we expect to establish a novel brain organoid model for LGGs, which will enable us to assess the specific roles of IDH mutations and other glioma-associated genetic mutations in tumorigenesis. The project will ultimately facilitate identification of novel drug targets and development of new therapies to treat gliomas.