Figure 2.

Overview of ChP-CSF–brain interactions. In addition to secreting CSF, ChP epithelial cells secrete morphogens and proteins with sites of action within the ChP (e.g., Shh on vasculature and ChP progenitor cells) and beyond the ChP on neural stem cells (e.g., IGF2 on cerebral cortical progenitor cells, and cytokines on adult neural stem cells). The ChP can be the site of tumorigenesis (brown). It also plays a role in protecting the brain from Aβ toxicity. Because there is an exchange between the brain's interstitial fluid and CSF (perforated line), the ratio of phosphorylated Tau:Aβ provides an early diagnostic for Alzheimer's disease and can predict the severity of neurodegenerative decline. Recent advances have made possible the engineering and production of ES-derived ChP epithelial cells (green).