Rett syndrome is a neurodevelopmental disorder caused by mutations in a transcriptional modulator gene, methyl CpG-binding protein 2 (MECP2). Mouse models with MeCP2 deletion recapitulate Rett-like symptoms. Reintroduction of MeCP2 in adult mice was shown to rescue the mutant phenotype, pointing to the possibility that Rett syndrome is a treatable disorder even if MeCP2 or its downstream signaling pathway is restored in adulthood. Administration of a tripeptide form of IGF1, a growth factor that is important for neuron survival and synaptic maturation, was found to partially reverse Rett symptoms in a mouse model. However, the detailed disease mechanisms and affected signaling pathways remain elusive, making identification of therapeutic targets for treating Rett patients difficult. To overcome these limitations, we are using pluripotent stem cell approach to derive mature neurons from reprogrammed adult somatic cells from Rett patients for studying disease mechanisms and discovering therapeutics. Using viral-mediated delivery of reprogramming factors, we have generated several lines of patient and control fibroblast-derived induced pluripotent stem cells (iPSCs) that carry various mutations in MECP2. Neural progenitor (NP) cells were successfully derived from these iPSC clones and were characterized using immunocytochemical methods that demonstrated that these cells are homogenous and express stage-appropriate markers. Upon long-term culturing on laminin coated surface up to 10 weeks, these NP cells differentiate into neurons as demonstrated by the detection of lineage specific proteins using immunocytochemistry. We are able to further examine these neurons with patch clamp recording and calcium imaging techniques to assess function and the extent of their maturation. Finally, we are looking into specific signaling pathways that underlie disease mechanisms. Based upon these findings, we are developing high-throughput cellular screening assays using automated microscopy and pathways-selective reporter genes to decipher differences in signaling mechanisms between Rett patient specific neurons and healthy controls.

International Society for Stem Cell Research, 2011.