Two main applications of stem cells in regenerative medicine involve cell replacement therapies and building human “disease-in-a dish” models to reveal underlying cellular and molecular events and to enable drug screenings. One of the major challenges of using “disease-in-a-dish” models is to reveal physiologically-relevant phenotypes and to use the phenotype for drug screening. Over the past several years, our laboratory has been working actively towards using human stem cell–based “disease-in-a-dish” models to study human neurological disorders. We have found that at least for neurological diseases, two universal assays can be applied. One is electrophysiological analysis for sensitive detection of abnormalities in synaptic transmission , as vast majority of neurological disorders involve abnormalities in neural transmission, and the other is alterations in transcriptome. Since it is increasingly acknowledged that the transcriptome of a cell to a large extent, represents the biological/physiological state of that cell, it is becoming meaningful to utilize the transcriptome as a general readout that marks the epigenetic state of a cell, which may reflect its pathological state, identity, differentiation and physiological state. Once the whole genome-wide transcriptome is reduced to a core/signature program of a handful of genes, there is a highly sensitive and quantitative medium-throughput screening platform, which can be used for core-transcriptome reversal screening that can also be considered as an universal phenotypic reversal screening. This application is aimed at testing the validity of this approach and if successful, it will greatly accelerate the drug discovery process using the human disease-in-a-dish models for neurological disorders, paving the way from disease genes all the way to therapeutic development.
Rett Syndrome (RTT) is a progressive neurodevelopmental disorder caused by primarily loss-of-function mutations in the X-linked MeCP2 gene. It mainly affects females with an incidence of about 1 in 10,000 births. After up to 18 months of apparently normal development, children with RTT develop severe neurological symptoms including motor defects, mental retardation, autistic traits, seizures and anxiety. RTT is one of the Autism Spectrum Disorders (ASDs) that affects many children in California. In this application, we propose to use our hESC-based Rett syndrome (RTT) model as a proof-of-principle case to define a set of core transcriptome that can be used for drug screenings. Human embryonic stem cells (hESCs) hold great potential for cell replacement therapy where cells are lost due to disease or injury. For the diseases of the central nervous system, hESC-derived neurons could be used for repair. This approach requires careful characterization of hESCs prior to utilizing their therapeutic potentials. Our findings will not only benefit RTT and other ASD patients, but also subsequently enable broad applications of this approach in drug discovery using human pluripotent stem cell-based disease models to benefit the citizens of California in a broader spectrum.