GSE120074
ASCL1 is directly activated by the LMO1 and MYCN oncogenes and is a master regulator of the differentiation program in neuroblastoma
Neuroblastoma is an embryonal tumor of the peripheral sympathetic nervous system.  Elevated expression of the transcription factor LMO1 and the polymorphisms within this gene are associated with the susceptibility to develop neuroblastoma.  LMO1 has been implicated as an oncogene in T-cell acute lymphoblastic leukemia; however, the transcriptional targets regulated by this protein in neuroblastoma cells are unknown.  Here, we identify the genes and molecular pathways controlled by LMO1 in neuroblastoma cells.  ChIP-seq analysis revealed that LMO1-bound regions are frequently co-occupied by GATA3 and MYCN proteins and are associated with active histone marks in neuroblastoma cells.  RNA-seq analysis demonstrated that LMO1 regulates gene expression in a tumor type-specific manner.  One high-confidence target gene directly regulated by LMO1 and MYCN is ASCL1, which is more highly expressed in adrenergic subtype of neuroblastoma cells as compared to normal neuronal cells.  High levels of ASCL1 expression are associated with inferior overall survival in primary human neuroblastoma cases.  ChIP-seq analysis identified a regulatory element controlling ASCL1 expression that is bound by LMO1, MYCN and the members of the core regulatory circuitry in neuroblastoma cells.  Furthermore, ASCL1 is required for neuroblastoma cell growth and regulates genes responsible for repression of neuronal cell differentiation.  Taken together, our results implicate ASCL1 as a critical downstream target of LMO1 in the molecular pathogenesis of neuroblastoma. Overall design: ChIP-Seq for LMO1 in the Kelly neuroblastoma cell line