Generation of human pluripotent stem cell reporter lines for the isolation of and reporting on astrocytes generated from ventral midbrain and ventral spinal cord neural progenitors.

Astrocytes play a critical role during the development and the maintenance of the CNS in health and disease. Yet, their lack of accessibility from fetuses and from the brain of diseased patients has hindered our understanding of their full implication in developmental and pathogenic processes. Human pluripotent stem cells (PSCs) are an alternative source to obtain large quantities of astrocytes in vitro, for mechanistic studies of development and disease. However, these studies often require highly pure populations of astrocytes, which are not always achieved, depending on the PSC lines and protocols used. Here, we describe the generation and characterization of human PSC reporter lines expressing TagRFP driven by the ABC1D region of the human GFAP promoter, as new cellular model for generating homogenous population of astrocytes generated from CNS regionally defined PSC-derived neural progenitors. GFA(ABC1D)::TagRFP-expressing astrocytes can be purified by fluorescent-activated cell sorting and maintain a bright expression for several additional weeks. These express canonical astrocyte markers NF1A, S100ß, CX43, GLAST, GS and CD44. These new cellular models, from which highly pure populations of fluorescence-expressing astrocytes can be obtained, provide a new platform for studies where pure or fluorescently labeled astrocyte populations are necessary, for example to assess pro-inflammatory cytokine and chemokine release in response to specific treatment, and uptake and degradation of fluorescently labeled pathogenic proteins, as reported in this study.