ASH1L mediated transcription networks in autism spectrum disorders

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ABSTRACT Genetic research in autism spectrum disorder (ASD) has led to the discovery of a growing list of highly penetrant mutations in chromatin modifiers and transcription factors. This recent progress provides an important opportunity to define the molecular mechanisms in ASD, as well as to identify targets for new treatment strategies. However, given the large number of seemingly independent ASD risk factors, a major challenge for ASD research is to establish convergent mechanisms that group apparently distinct genetic etiologies. We identified a novel point of convergence between the histone-methyltransferase ASH1L, a major ASD genetic risk factor, and a cluster of ASD high-risk genes (e.g. FOXP1, RIMS1, NRX1a). We also find that ASH1L counteracts the activity of Polycomb repressor complex in neural development. Hence, our data uncover a transcriptional and epigenetic node linked to cell and circuit dysfunction underlying ASD phenotypes. However, the transcriptional programs modulated by ASH1L that lead to neuronal dysfunction are understudied. Our central hypothesis is that ASH1L counteracts Polycomb activity to orchestrate neuronal development by modulating transcriptional programs that control synaptic function and neuronal morphogenesis. We will define how ASH1L regulates neuronal development and function. We will use a multilevel, synergistic and translational approach that leverages human and mouse systems to determine how ASH1L modulates neuronal programs relevant to ASD pathogenesis. We are positioned to undertake this work, based on our robust preliminary data and combined expertise in cellular/molecular neuroscience, bioinformatic, chromatin biology and electrophysiology. 1) Determine how mutations in ASH1L disrupt neuronal arborization and function in human stem cell experimental systems, 2) Define functional and circuit phenotypes associated with ASH1L in rodent systems. 3) Define bulk and cell type specific epigenetic and transcriptional signatures associated with ASH1L mutations that cause disease in mouse and human neurons. Finally, we will define rescue strategies for the cellular, molecular, and electrophysiological phenotypes observed in both mouse and human experimental systems.