SISTEMA: A large and standardized collection of transcriptome data sets for human pluripotent stem cell research

Human iPSC-derived-keratinocytes, a useful model to identify and explore pathological phenotype of Epidermolysis Bullosa Simplex

Epidermolysis Bullosa Simplex (EBS), an autosomal dominant skin disorder, is characterized by skin fragility. Genetically, majority of cases are related to missense mutations in two keratin genes, KRT5 or KRT14, leading to cytolysis of basal keratinocytes and intraepidermal blistering. Progress towards identification of treatments have been hampered by incomplete understanding of the mechanisms underlying this disease, and availability of relevant and reliable in vitro models recapitulating the physiopathological mechanisms. Recent advances in stem cell field have fueled the prospect that these limitations could be overcome thanks to the availability of disease-specific human induced pluripotent stem cells (hiPSC). Here, we generated hiPSC-derived keratinocytes from patients carrying KRT5 dominant mutations and compared them to non-affected hiPSC-derived keratinocytes as well as their primary counterparts. Our results demonstrated that EBS hiPSC-derived keratinocytes displayed proliferative defects, increased capacity to migrate, alteration of ERK signaling pathway and cytoplasmic keratin filament aggregates as observed in primary EBS keratinocytes. Of interest, EBS hiPSC-derived keratinocytes exhibited a downregulation of hemidesmosomal proteins revealing the different effects of KRT5 mutations on keratin cytoskeletal organization. Combination of culture miniaturization and treatment with the chaperone molecule 4-PBA, our results demonstrated that hiPSC-derived keratinocytes represent a suitable model for identifying novel therapies for EBS.

CRISPR gene editing in pluripotent stem cells reveals the function of MBNL proteins during human in vitro myogenesis

Alternative splicing has emerged as a fundamental mechanism for the spatiotemporal control of development. A better understanding of how this mechanism is regulated has the potential not only to elucidate fundamental biological principles, but also to decipher pathological mechanisms implicated in diseases where normal splicing networks are misregulated. Here, we took advantage of human pluripotent stem cells to decipher during human myogenesis the role of muscleblind-like (MBNL) proteins, a family of tissue-specific splicing regulators whose loss of function is associated with myotonic dystrophy type 1 (DM1), an inherited neuromuscular disease. Thanks to the CRISPR/Cas9 technology, we generated human-induced pluripotent stem cells (hiPSCs) depleted in MBNL proteins and evaluated the consequences of their losses on the generation of skeletal muscle cells. Our results suggested that MBNL proteins are required for the late myogenic maturation. In addition, loss of MBNL1 and MBNL2 recapitulated the main features of DM1 observed in hiPSC-derived skeletal muscle cells. Comparative transcriptomic analyses also revealed the muscle-related processes regulated by these proteins that are commonly misregulated in DM1. Together, our study reveals the temporal requirement of MBNL proteins in human myogenesis and should facilitate the identification of new therapeutic strategies capable to cope with the loss of function of these MBNL proteins.