Project description:We have previously developed a cocktail of nine small molecules to convert human fetal astrocytes into neurons, but a nine-molecule recipe is difficult for clinical applications. Here, we identify a chemical formula with only three to four small molecules for astrocyte-to-neuron conversion. We demonstrate that modulation of three to four signaling pathways among Notch, glycogen synthase kinase 3, transforming growth factor ?, and bone morphogenetic protein pathways is sufficient to change an astrocyte into a neuron. The chemically converted human neurons can survive >7 months in culture, fire repetitive action potentials, and display robust synaptic burst activities. Interestingly, cortical astrocyte-converted neurons are mostly glutamatergic, while midbrain astrocyte-converted neurons can yield some GABAergic neurons in addition to glutamatergic neurons. When administered in vivo through intracranial or intraperitoneal injection, the four-drug combination can significantly increase adult hippocampal neurogenesis. Together, human fetal astrocytes can be chemically converted into functional neurons using three to four small molecules, bringing us one step forward for developing future drug therapy.
Project description:Direct reprogramming approaches offer an attractive alternative to stem-cell-derived models, allowing the retention of epigenetic information and age-associated cellular phenotypes. To explore such age-related phenotypes, several groups have generated multiple neuronal subtypes, neural progenitor cells, oligodendrocytes, and other cell types directly from fibroblasts. Other groups have had success at the efficient conversion of embryonic fibroblasts to astrocytes but have not yet achieved similar conversion efficiency for adult human fibroblasts. In order to generate astrocytes for the study of age-related diseases, we developed an improved direct conversion strategy employing a combination of small molecules to activate specific pathways that induce trans-differentiation of human adult fibroblasts to astrocytes. We demonstrate that this method produces mature GFAP+/S100β+ cells at high efficiency (40-45%), comparable to previous studies utilizing embryonic fibroblasts. Further, Fibroblast-derived induced Astrocytes (FdiAs) are enriched for markers of astrocyte functionality, including ion-channel buffering, gap-junction communication, and glutamate uptake; and exhibit astrocyte-like calcium signaling and neuroinflammatory phenotypes. RNA-Seq analysis indicates an adult rather than fetal astrocytic gene expression signature, with a greater correlation to temporal lobe astrocytes. Fibroblast-derived induced astrocytes provide a useful tool in understanding age-associated disease processes and complement existing in vitro models of induced neurons (iNs), providing an additional platform to study late-stage brain disorders.
Project description:Direct reprogramming approaches offer an attractive alternative to stem-cell-derived models, allowing the retention of epigenetic information and age-associated cellular phenotypes, as well as a fast method to reach a target cell type. Several groups have previously generated multiple neuronal subtypes, neural progenitor cells, oligodendrocytes, and other cell types directly from fibroblasts. Other groups have had success at the efficient conversion of embryonic fibroblasts to astrocytes but have not yet achieved similar conversion efficiency for adult human fibroblasts. In order to generate astrocytes for the study of adult-stage disorders, we developed an improved direct conversion strategy employing a combination of small molecules to activate specific pathways that induce trans-differentiation of human adult fibroblasts to astrocytes. We demonstrate that this method produces mature GFAP+/S100β+ cells at high efficiency (40-45%), comparable to previous studies utilizing embryonic fibroblasts. Further, Fibroblast-derived induced Astrocytes (FdiAs) are enriched for markers of astrocyte functionality, including ion-channel buffering, gap-junction communication, and glutamate uptake; and exhibit astrocyte-like calcium signaling and neuroinflammatory phenotypes. RNA-Seq analysis indicates an adult rather than fetal astrocytic gene expression signature, with a greater correlation to temporal lobe astrocytes. Fibroblast-derived induced astrocytes provide a useful tool in studying the adult brain and complement existing in vitro models of induced neurons (iNs), providing an additional platform to study late-stage brain disorders.
Project description:We used microarrays to detail the transcriptome-wide gene expression changes underlying chemical conversion of human fibroblasts into induced Schwann Cells over a time period of 39 days. We compared then the expression profiles of these induced Schwann Cells to primary Schwann cells. The gene expression results analyzed in this study are further described in Thoma et al. (2014) Chemical conversion of human fibroblasts into functional Schwann cells. Under submission
Project description:Using multi-omics analyses including RNAseq, RT-PCR, RACE-PCR, and shotgun proteomic with enrichment strategies, we demonstrated that newborn rat astrocytes produce neural immunoglobulin constant and variable heavy chains as well as light chains. However, their edification is different from the ones found in B cells and resembles aberrant immunoglobulins as observed in several cancers. Moreover, the complete enzymatic V(D)J recombination complex has also been identified in astrocytes. In addition, the constant heavy chain is also present in astrocytes adult rats, whereas in primary astrocytes from human fetal astrocytes we identified constant and variable kappa chains as well as the substitution lambda chains known to be involved in pre-B cells. To gather insights into the function of these neural IgGs, CRISPR-Cas9 IgG2B constant heavy chain (IgH6), overexpression, proximal labeling of rat astrocytes IgH6 and targets identification through 2D gels were performed. In CRISPR-Cas9 IgG2B KO, overexpression of factors involved in hematopoietic cells, neural stem cells and the regulation of neuritogenesis have been identified. Moreover, overexpression of IgG2B in astrocytes induces the CRTC1-CREB-BDNF signaling pathway known to be involved in gliogenesis whereas CRISPR-Cas9 IgG2B KO triggers the BMP/YAP1/TEAD3 pathway activated in astrocytes dedifferentiation into neural progenitors. Proximal labeling experiments revealed that IgG2B is N-glycosylated by the OST complex, addressed to vesicle membranes containing the ATPase complex; and behaves partially like CD98hc through its association with LAT1. Proximity-dependent biotin labeling experiments suggest that proximal IgG2B-LAT1 interaction occurs concomitantly with MACO-1 and C2CD2L, at the heart of a potentially novel cell signaling platform. Finally, we demonstrated that these chains are synthesized individually and associated to recognize specific targets. Indeed, intermediate filaments Eif4a2 and Pdia6 involved in astrocyte fate constitute targets for these neural IgGs. Taken together, we hypotheses that aberrant neural IgG chains may act as gatekeepers of astrocytes fate.
Project description:Direct cell reprogramming has enabled the direct conversion of skin fibroblasts into functional neurons and oligodendrocytes using a minimal set of cell lineage-specific transcription factors. This approach has substantial advantages since it is rapid and simple, generating the cell type of interest in a single step. However, it remains unknown whether this technology can be applied for directly reprogramming skin cells into astrocytes, the third neural lineage. Astrocytes play crucial roles in neuronal homeostasis and their dysfunctions contribute to the origin and progression of multiple human diseases. Herein, we carried out a screening using several transcription factors involved in defining the astroglial cell fate and identified NFIA, NFIB and SOX9 to be sufficient to convert with high efficiency embryonic and post-natal mouse fibroblasts into astrocytes (iAstrocytes). We proved both by gene expression profiling and functional tests that iAstrocytes are comparable to native brain astrocytes. This protocol can be then employed to generate functional iAstrocytes for a wide range of experimental applications. Induced astrocytes (iAstro) were compared to Fibroblasts (Fibro) as negative control and to primary astrocytes (astro) as positive control. Three biological replicates were analyzed for each experimental group.
Project description:To characterize the transcriptome of our cultured human astrocyte cell line, RNA-seq was performed and the data were compared with other available datasets.
Project description:Conversion of cellular identity can be achieved safely, without genetic manipulation, by inducing signalling perturbations with chemical compounds to target cell fate-governing transcription factors (TFs). However, chemical-induced cellular conversion currently requires large-scale screening of small compounds, which is time- and labour-intensive. There are no existing computational approaches that facilitate chemical conversion of cell fate. Here, we develop a computational framework (SiPer) to systematically predict chemical compounds specifically targeting desired sets of TFs to direct cellular conversion. This framework integrates a large compendium of chemical perturbation datasets with a network model. We show that SiPer is generally applicable to diverse cellular conversion examples, recapitulating the known chemical compounds and their corresponding protein targets. Furthermore, using chemical compounds predicted by SiPer, we develop a highly efficient protocol for the generation of functional human induced hepatocytes (hiHeps). These results demonstrate that SiPer provides a valuable resource to efficiently identify chemical compounds for cellular conversion.