Second, and even more stunning, the implanted human cells not only integrate into the recipient brains, but over time predominate; they first displace and then ultimately replace the resident glial populations of their hosts. In both shiverers and myelin wild-type recipients, colonization of the cortical and subcortical gray by migrating hGPCs is followed first by their selective expansion, and then by the inexorable displacement and in situ death of resident murine glial progenitors (Windrem et al. 2014). As a result of this apparent competition between resident mouse GPCs and the invading human GPCs, by a year of age the donor hGPCs are typically distributed in a relatively uniform manner throughout the forebrain white and gray matter, while mouse GPCs are scarce, and often absent from the now human glial-dominant forebrains.
