Familial dysautonomia is a rare and fatal peripheral neuropathy caused by a mutation in the gene IKBKAP that encodes a protein involved in transcriptional elongation. Lee et al. report the derivation of patient-specific iPS (induced pluripotent stem) cells and the directed differentiation into cells of all three germ layers including peripheral neurons. Gene expression analysis revealed tissue-specific mis-splicing of IKBKAP in vitro, with the patients' neural crest precursors expressing particularly low levels of normal IKBKAP transcript, suggesting a mechanism for disease specificity. Transcriptome analysis and cell-based assays showed defects in neurogenic differentiation and migration behaviour. This work is a step towards using iPS technology to produce relevant human disease models, and in functional assays for the identification of candidate drugs. The derivation and differentiation of disease-specific human induced pluripotent stem cells (iPSCs) offers a new strategy for modelling disease. Familial dysautonomia (FD) is a rare but fatal peripheral neuropathy caused by a mutation in the IKBKAP gene. Here, patient-specific FD-iPSCs are derived and differentiated into cells of all three germ layers, including peripheral neurons; the cells are then analysed for mechanism of disease specificity and response to candidate drugs. The isolation of human induced pluripotent stem cells (iPSCs)1,2,3 offers a new strategy for modelling human disease. Recent studies have reported the derivation and differentiation of disease-specific human iPSCs4,5,6,7. However, a key challenge in the field is the demonstration of disease-related phenotypes and the ability to model pathogenesis and treatment of disease in iPSCs. Familial dysautonomia (FD) is a rare but fatal peripheral neuropathy, caused by a point mutation in the IKBKAP8 gene involved in transcriptional elongation9. The disease is characterized by the depletion of autonomic and sensory neurons. The specificity to the peripheral nervous system and the mechanism of neuron loss in FD are poorly understood owing to the lack of an appropriate model system. Here we report the derivation of patient-specific FD-iPSCs and the directed differentiation into cells of all three germ layers including peripheral neurons. Gene expression analysis in purified FD-iPSC-derived lineages demonstrates tissue-specific mis-splicing of IKBKAP in vitro. Patient-specific neural crest precursors express particularly low levels of normal IKBKAP transcript, suggesting a mechanism for disease specificity. FD pathogenesis is further characterized by transcriptome analysis and cell-based assays revealing marked defects in neurogenic differentiation and migration behaviour. Furthermore, we use FD-iPSCs for validating the potency of candidate drugs in reversing aberrant splicing and ameliorating neuronal differentiation and migration. Our study illustrates the promise of iPSC technology for gaining new insights into human disease pathogenesis and treatment.

Human induced pluripotent stem cells show no consistent differences from human embryonic stem cells in a study that controls for several sources of variability. The equivalence of human induced pluripotent stem cells (hiPSCs) and human embryonic stem cells (hESCs) remains controversial. Here we use genetically matched hESC and hiPSC lines to assess the contribution of cellular origin (hESC vs. hiPSC), the Sendai virus (SeV) reprogramming method and genetic background to transcriptional and DNA methylation patterns while controlling for cell line clonality and sex. We find that transcriptional and epigenetic variation originating from genetic background dominates over variation due to cellular origin or SeV infection. Moreover, the 49 differentially expressed genes we detect between genetically matched hESCs and hiPSCs neither predict functional outcome nor distinguish an independently derived, larger set of unmatched hESC and hiPSC lines. We conclude that hESCs and hiPSCs are molecularly and functionally equivalent and cannot be distinguished by a consistent gene expression signature. Our data further imply that genetic background variation is a major confounding factor for transcriptional and epigenetic comparisons of pluripotent cell lines, explaining some of the previously observed differences between genetically unmatched hESCs and hiPSCs.

Lee et al. use neural crest precursor cells derived from patient-specific induced pluripotent stem cells to screen a small-molecule library for compounds that correct the cellular phenotype of familial dysautonomia. Patient-specific induced pluripotent stem cells (iPSCs) represent a novel system for modeling human genetic disease and could provide a source of cells for large-scale drug-discovery screens. Here we demonstrate the feasibility of performing a primary screen in neural crest precursors derived from iPSCs that were generated from individuals with familial dysautonomia (FD), a rare, fatal genetic disorder affecting neural crest lineages. We tested 6,912 small-molecule compounds and characterized eight that rescued expression of IKBKAP, the gene responsible for FD. One of the hits, SKF-86466, was found to induce IKBKAP transcription through modulation of intracellular cAMP levels and PKA-dependent CREB phosphorylation. SKF-86466 also rescued IKAP protein expression and the disease-specific loss of autonomic neuronal marker expression. Our data implicate alpha-2 adrenergic receptor activity in regulating IKBKAP expression and demonstrate that small-molecule discovery using an iPSC-based disease model can identify candidate drugs for potential therapeutic intervention.

Duchenne muscular dystrophy (DMD) remains an intractable genetic disease. Althogh there are several animal models of DMD, there is no human cell model that carries patient-specific DYSTROPHIN mutations. Here, we present a human DMD model using human induced pluripotent stem cells (hiPSCs). Our model reveals concordant disease-related phenotypes with patient-dependent variation, which are partially reversed by genetic and pharmacological approaches. Our "chemical-compound-based" strategy successfully directs hiPSCs into expandable myoblasts, which exhibit a myogenic transcriptional program, forming striated contractile myofibers and participating in muscle regeneration in vivo. DMD-hiPSC-derived myoblasts show disease-related phenotypes with patient-to-patient variability, including aberrant expression of inflammation or immune-response genes and collagens, increased BMP/TGFβ signaling, and reduced fusion competence. Furthermore, by genetic correction and pharmacological "dual-SMAD" inhibition, the DMD-hiPSC-derived myoblasts and genetically corrected isogenic myoblasts form "rescued" multi-nucleated myotubes. In conclusion, our findings demonstrate the feasibility of establishing a human "DMD-in-a-dish" model using hiPSC-based disease modeling.