Spatial and Single Cell Transcriptomics Approach to Understand Neuron-Oligodendrocyte Communication in Human Synaptic Development - ABSTRACT Oligodendrocytes are the myelinating glia cells of the central nervous system allowing coordinated conduction of action potentials among neurons, thus imperative for proper neurological functions. The vast majority of our knowledge in oligodendrocytes is derived from rodent models. Perhaps for that reason, clinical translation of our knowledge has been limited, leaving many disorders without treatment. In order to understand the fundamental human oligodendrocyte development, pathology, and ultimately to discover drug candidates with higher confidence, therefore, it is necessary to develop protocols in human-based platform. Single-cell RNA sequencing comparing mouse and human oligodendrocyte precursor cells (OPCs) revealed a compelling unique sub- population in human OPCs that does not seem to exist in mouse OPCs. More importantly, gene ontology analysis of this sub-population identified highly expressed signature genes associated with synaptic development, organization, and transmission, suggesting neuron-oligodendrocyte communication during neuronal development. To our knowledge, there are no reports suggested a direct synaptic control by OPCs. Based on these observations, we hypothesize that a sub-population of human OPCs regulates synaptic development. This proposal intends to establish concrete evidence for human-specific OPC sub-population through two pilot experiments to prepare for a future external funding focusing on understanding the molecular mechanisms of human synaptic development controlled by OPCs. First, to define temporal and spatial interaction between human specific OPC sub-population and neurons, we will generate spatial transcriptomic profiling of developing human brain spanning gestational week 10 to 24, when dynamic synaptic development as well as OPC maturation occur. Spatial transcriptomics uses an intact tissue section mounted on a slide that is coated with arrays of barcoded RT primers to create spatially barcoded cDNA, allowing us to obtain transcriptomic data from the entire tissue retaining spatial information. These data will reveal where the OPC sub-population exists in developing brains and what type(s) of neighboring neurons they are interacting with. Second, we will begin to test the function of human specific OPC sub-population using quantitative electrophysiology in a co-culture and slice culture formats that we have optimized. Once achieved, these studies will lay the foundation to study a novel function of human OPC sub-population. Generated transcriptomic datasets will allow us to formulate testable hypotheses for future external grants. In a larger perspective, discovery of a new mechanism in synaptic control may lead to a re-formulation of the pathomechanisms in diseases with suspected involvement of oligodendrocytes, such as intellectual disabilities and neuropsychiatric disorders.
