Recent studies identified a fast growing list of long noncoding RNAs (lncRNAs) that harbor greater than 200 nucleotides with no open reading frames but play key roles in regulating gene expression thus govern neural stem cell maintenance, neurogenesis, neuronal network assembly, and synaptic plasticity. The lncRNA transcriptome is strikingly expanded in human during evolution and most abundantly expressed in the brain. The complexity of human lncRNAs is thought to underlie the major architect of cognitive evolution but also introduce vulnerabilities for various brain diseases. Indeed, lncRNA dysregulation is observed in autism, intellectual disability, epilepsy, neurodegenerative disorders and neuropsychiatric diseases, suggesting that lncRNA dysregulation contributes to the pathogenesis of various brain illnesses. However, our current understanding of regulation and function of lncRNAs in human neurons are still in the infancy. The lncRNA Gomafu, a transcript initially identified to associate with myocardial infarction thus named MIAT, was recently found to be most abundant in the brain and implicated in normal neuronal development and cognitive conditions. Gomafu is quickly downregulated upon synaptic stimulation and fear-conditioning. In addition, Gomafu knockout mice display anxiety-like behaviors. In neurons derived from human induced- pluripotent stem cells (hiPSCs), Gomafu regulates alternative splicing (AS) of primary transcripts essential for neuronal development and synaptic function. Importantly, Gomafu dysregulation is detected in cortical grey matters and interneurons of post-mortem brains derived from schizophrenia patients. These discoveries together suggest that Gomafu plays essential roles in governing normal brain function. However, molecular mechanisms that regulate human Gomafu expression remain unexplored. How Gomafu is dysregulated in brain diseases is not understood. Moreover, how Gomafu controls AS of the human neuronal transcriptome remains elusive. How Gomafu deficiency affects human neuron development is unknown. This proposal attacks these important questions, aiming to 1) Delineate molecular mechanisms and pathways that regulate Gomafu expression in hiPSC-derived neurons, especially regarding a genetic-epigenetic interaction network centering on a novel microRNA-lncRNA functional interplay revealed by our preliminary data; 2) determine the alternative splicing targets of Gomafu in human neuronal transcriptome by deep RNA-sequencing; 3) determine the function of Gomafu in the development of hiPSC-derived cortical excitatory neurons and dopaminergic neurons in 2-D culture and 3-D organoids. Answers to these questions will fill prevailing knowledge gaps regarding how lncRNAs govern normal development of human neurons and lncRNA malfunction in brain disorders.
Successful completion of the proposed studies will greatly advance our current knowledge regarding how noncoding RNA-mediated epigenetic regulation governs normal human neuron development and their contribution to the complex etiology of various cognitive and neurological diseases, which is a critical prerequisite for developing novel diagnosis biomarkers and/or therapeutic strategies against brain illnesses.
