Generation of MGE-like cells from human pluripotent stem cells

The dysfunction of MGE-derived interneurons has been linked to many neuropsychiatric disorders. The MGE has been shown to be patterned by the WNT and sonic (SHH)signalling pathways. Published protocols have attempted to replicate in vitro the MGE environment, by WNT inhibition and SHH activation, in order to generate MGE-like interneurons from hPSCs. However, in these protocols, very long periods of maturation and cell transplantation are required in order to obtain a substantial amount of MGE-like interneurons, especially those expressing Parvalbumin (PV). This thesis proposes a differentiation protocol for the production of MGE-like cells exclusively in vitro. This protocol was established by determining the optimal concentration of WNT and SHH. Single cell RNA expression analysis by FISH and single cell qRT PCR revealed that the majority of differentiated neurons became Somatostatin (SST) expressing INs and almost 10% of cells expressed PV. This was greater than what other studies obtained exclusively in vitro after only 50 days of neuronal differentiation. The cells produced were electro-physiologically functional when co-cultured with rat astrocytes. Single cell RNA sequencing was utilised to evaluate the efficiency of the protocol by comparing the expression profile of progenitor cells to a published single cell data of an in vitro model of human interneurons. Results indicated that the protocol produced a population of progenitor cells which resembled those derived from the MGE. Interestingly, 10% of progenitor cells started expressing PV. This early PV expression was also observed in vivo in another published single cell data. In conclusion, progenitors and mature interneurons which resemble those derived from the MGE can be generated from hPSCs using the optimised neuronal differentiation protocol presented in this thesis. This will be valuable forstudying and modelling neurodevelopment and neuropsychiatric disorders in which MGE derived interneurons play an important role