PTN and Alzheimer disease: The analysis of the communication between neurons and astrocytes in AD showed a significant rise in both incoming and outgoing signals for neural cell adhesion molecule (NCAM), neuregulin (NRG), cell adhesion molecule (CADM), and contactin (CNTN) (Fig. 3h, i); Conversely, there was a decrease in both incoming and outgoing signals for pleiotrophin (PTN) when compared to GBM (Fig. 3h, i).