Defining fate potential in human ESC derived neural stem cells

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: Neural stem cells (NSCs) can be propagated in vitro for extensive periods of time while retaining the ability to differentiate into neurons, astrocytes and oligodendrocytes. However, NSCs are limited in their potential to yield specific neuron types. Na¿ve NSCs expanded in vitro give rise primarily to GABAergic interneurons and to a lesser extent glutamate neurons. This suggests that NSCs, while multipotent, may not have access to the full spectrum of neuron types. In contrast human embryonic stem cells (hESCs) differentiated towards early neural fates can be readily biased towards various region-specific neuron types such as midbrain dopamine neurons or spinal motoneurons. We have recently reported that hESC derived neural progeny responsive to such regional patterning cues are organized into columnar neuroepithelial structures termed neural rosettes (R- NSCs) and characterized R-NSCs in considerable detail1. Our study has identified R-NSCs as novel, unique NSC stage based on marker expression, clonal stem cell properties, neural differentiation potential, and genetic identity1, 2. The most intriguing finding of these studies was the broad patterning potential of R-NSCs compared to other currently available NSC types. R-NSCs are capable of comprehensive differentiation towards CNS1 and PNS3 derivatives and capable of in vivo engraftment. Despite these exciting preliminary data our studies also revealed major gaps in our current understanding of RNSC biology. Here we would like to address some of these limitations by defining heterogeneity within RNSCs and develop genetic strategies for the prospective isolation of fully patternable R-NSCs based on BAC transgenesis. BAC transgenic hESC reporter lines have been recently pioneered in the Studer lab and will serve as reliable readout of R-NSC stage, identity and function. BAC transgenic reporters will also be critical for probing function of extrinsic and intrinsic factors affecting R-NSC identity. These studies should provide fundamental insights into the genetic and epigenetic mechanisms of neural patterning and ultimately result in novel conditions for the continued in vitro expansion of fully patternable R-NSC - a key step towards establishing a stable expandable universal NSC population.