first identified based on their expression of human nuclear antigen (hNuclei). The hNuclei+ cells were found to distribute relatively evenly throughout the forebrain, infiltrating both hippocampus and cortex (Fig. 1B). Human astrocytes were specifically identified by their intricate EGFP+ fluorescent processes, and in fixed tissue by their co-expression of human glial fibrillary acidic protein (hGFAP) and hNuclei (Fig. 1C). By 4-5 months of age, mice engrafted with human GPCs exhibited substantial addition of human astrocytes to both the hippocampus and deep neocortical layers; by 12-20 months, human astrocytes further populated large regions of the amygdala, thalamus, neostriatum and cortex (Fig. 1D-F). The human astrocytes appeared to develop and mature in a cell-autonomous fashion, maintaining their larger size and more complex structure relative to murine astrocytes (Fig. 1G-H).
