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Sorting of Sox1-GFP Mouse Embryonic Stem Cells Enhances Neuronal Identity Acquisition upon Factor-Free Monolayer Differentiation.

ABSTRACT: Embryonic stem cells (ESCs) can give rise to all the differentiated cell types of the organism, including neurons. However, the efficiency and specificity of neural differentiation protocols still needs to be improved in order to plan their use in cell replacement therapies. In this study, we modified a monolayer differentiation protocol by selecting green fluorescent protein (GFP) positive neural precursors with fluorescence-activated cell sorting (FACS). The enhancement of neural differentiation was obtained by positively selecting for neural precursors, while specific neuronal subtypes spontaneously differentiated without additional cues; a comparable but delayed behavior was also observed in the GFP negative population, indicating that sorting settings per se eliminated nonneural and undifferentiated ESCs. This highly reproducible approach could be applied as a strategy to enhance neuronal differentiation and could be the first step toward the selection of pure populations of neurons, to be generated by the administration of specific factors in high throughput screening assays.

SUBMITTER: Incitti T

PROVIDER: S-EPMC4048977 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Little is known about the molecular mechanisms and intrinsic factors that are responsible for the emergence of neuronal subtype identity. Several transcription factors that are expressed mainly in precursors of the ventral telencephalon have been shown to control neuronal specification, but it has been unclear whether subtype identity is also specified in these precursors, or if this happens in postmitotic neurons, and whether it involves the same or different factors. SOX1, an HMG box transcription factor, is expressed widely in neural precursors along with the two other SOXB1 subfamily members, SOX2 and SOX3, and all three have been implicated in neurogenesis. SOX1 is also uniquely expressed at a high level in the majority of telencephalic neurons that constitute the ventral striatum (VS). These neurons are missing in Sox1-null mutant mice. In the present study, we have addressed the requirement for SOX1 at a cellular level, revealing both the nature and timing of the defect. By generating a novel Sox1-null allele expressing beta-galactosidase, we found that the VS precursors and their early neuronal differentiation are unaffected in the absence of SOX1, but the prospective neurons fail to migrate to their appropriate position. Furthermore, the migration of non-Sox1-expressing VS neurons (such as those expressing Pax6) was also affected in the absence of SOX1, suggesting that Sox1-expressing neurons play a role in structuring the area of the VS. To test whether SOX1 is required in postmitotic cells for the emergence of VS neuronal identity, we generated mice in which Sox1 expression was directed to all ventral telencephalic precursors, but to only a very few VS neurons. These mice again lacked most of the VS, indicating that SOX1 expression in precursors is not sufficient for VS development. Conversely, the few neurons in which Sox1 expression was maintained were able to migrate to the VS. In conclusion, Sox1 expression in precursors is not sufficient for VS neuronal identity and migration, but this is accomplished in postmitotic cells, which require the continued presence of SOX1. Our data also suggest that other SOXB1 members showing expression in specific neuronal populations are likely to play continuous roles from the establishment of precursors to their final differentiation.

Project description:The dentate gyrus of the hippocampus continues generating new neurons throughout life. These nerve cells originate from radial astrocytes within the subgranular zone (SGZ). We find that Sox1, a member of the SoxB1 family of transcription factors, is expressed in a subset of radial astrocytes. Lineage tracing using Sox1 driven reporter mice shows that the Sox1-expressing cells represent an activated neural stem/progenitor population. We used microarrays to evaluate the molecular constitution of neural stem cells with aging. Hippocampi were isolated from Sox1-GFP mice at 5-7 months (n=3) or 1 year 9 months (n=4) using a Leica dissecting scope. Cells were immediately dissociated using papain (Worthington Biochemical Corporation. Lakewood, NJ, USA) and sorted for the GFP high or GFP negative population using a FACSAria Flow Cytometer (BD Biosciences, San Diego, CA, USA). RNA was harvested using the Arcturus PicoPure RNA isolation kit (Life Technologies Corp, Carlsbad, CA, USA) and the quality and quantity of each sample was checked using Agilent BioAnalyzer (Santa Clara, CA, USA) and Nanodrop spectrophotometer (Wilmington, DE, USA). Samples were amplified using the NuGEN FFPE kit (San Carlos, CA, USA) and cDNA was prepared using an oligo(dT)-T7 RNA polymerase primer before biotinylation by in vitro transcription, partial hydrolysis and final hybridization to the Affymetrix (Santa Clara, CA, USA) GeneChip Mouse Gene 1.0 ST Array (Gladstone Genomics Core). Arrays were normalized using Robust Multichip Average (RMA) and the latest probe map to MM9 RefSeq genes (Irizarry et al., 2003; Dai et al., 2005). To detect potential outlier arrays, the distributions of fold changes between all possible pairs within each group were analyzed. One sample from a young mouse was found to have a skewed distribution when compared to other biological replicate samples and was removed from further analysis. The statistical package R was used to perform average linkage hierarchical clustering of the remaining samples. Significance Analysis of Microarrays (SAM) was performed to determine significant differentially expressed genes between the old and young mice with a False Discovery Rate cutoff of 5% (Tusher et al., 2001).

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Sorting of Sox1-GFP Mouse Embryonic Stem Cells Enhances Neuronal Identity Acquisition upon Factor-Free Monolayer Differentiation.

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