In addition to detailing recombinant P2X7 and polymorphic variants of canine P2X7, this article provides a comprehensive review of the molecular and functional expression of P2X7 in cells and tissues from dogs, with P2X7 reported in erythrocytes, T and B cells, monocytes, and macrophages as well as adipose stem cells, kidney cells, nervous system cells including brain cancers, and possibly myenteric plexus neurons. Here, P2RX7 is linked to brain cancer.