Abstract
H3.3G34-mutant high-grade glioma (HGG-G34) is a recently recognized subtype of brain tumor, defined by the presence of either a p.G34R or p.G34V mutation in the histone variant H3.3. HGG-G34 mainly affects adolescents and young adults, accounting for approximately 20% of hemispheric HGG cases in this age group. Despite intense treatment, patients face a dismal prognosis with a two-year overall survival rate of 27.3%. Therefore, there is an urgent need to elucidate the pathogenic mechanism and develop new therapeutic approaches. Recent studies indicate the presence of radial glia (RG)-like cells in HGG-G34. However, little is known about their clinical relevance and molecular mechanisms underlying the maintenance of RG identity. In this study, we identified the transcription factor DMRTA2 as a downstream effector of H3.3G34R mutation. DMRTA2 is highly and specifically expressed in HGG-G34 subtype compared to other subtypes of pediatric brain tumors. To investigate the functional role of DMRTA2, we first established DMRTA2 knockout (KO) human embryonic stem cell (hESC) lines by using CRISPR/Cas9 gene editing and differentiated them to cerebral organoids. DMRTA2 KO organoids exhibited smaller size and a decreased number of RG cells compared to DMRTA2 wildtype organoids. Next, DMRTA2 was knocked out in hESC-based HGG-G34 model cells we developed. DMRTA2 KO resulted in a decreased number of RG-like cells and reciprocally an enhanced neuronal differentiation. Furthermore, when transplanted into the brains of immunodeficient mice, DMRTA2 KO cells exhibited significantly reduced tumorigenicity. Taken together, our findings indicate an important role of DMRTA2 in the maintenance of RG identity as well as the formation of HGG-G34, paving the way for the development of new therapies against the devastating disease.