Rapid Generation of Regionally Specified CNS Neurons by Sequential Patterning and Conversion of Human Induced Pluripotent Stem Cells

The differentiation of patient-specific induced pluripotent stem cells (iPSCs) into specific neuronal subtypes has been exploited as an approach to modeling a variety of neurological disorders. However, achieving a highly pure population of neurons is challenging when using directed differentiation methods, especially for neuronal subtypes generated by complex and protracted protocols. In this study, we efficiently produced highly pure populations of regionally specified CNS neurons by using a modified NGN2-Puromycin direct conversion protocol. The protocol is amenable across a range of iPSC lines, with an efficiency above 97% by day 21, and above 95% of neurons positive for MAP2. This NGN2-Puromycin conversion resulted in a significant number of peripheral neurons, but by incorporating a short CNS patterning step, we eliminated these peripheral neurons. Furthermore, we used the patterning step to control the rostral-caudal identity. This approach to sequential patterning and NGN2-Puromycin conversion, when patterned with SMAD inhibitors, produced pure populations of forebrain neurons; when SMAD inhibitors and WNT agonists were applied, the approach produced anterior hindbrain excitatory neurons, resulting in a neuronal population containing VSX2/SHOX2 V2a interneurons. Overall, this sequential patterning and conversion protocol can be used for the production of a variety of CNS excitatory neurons from patient-derived iPSCs, which is a highly versatile system for investigating early disease events for a range of neurological disorders including Alzheimer's disease, motor neurons disease and spinal cord injury. Overall design: 12 samples in total. Triplicates of 4 conditions. H9 undifferentiated human embryonic stem cells are a control sample.