P2RX7 and Renal cyst: Although the gene sets for calcium/calcineurin/NFAT signaling were not significantly enriched (p = 0.14), we found that Crebbp (2.08 fold), P2rx7 (11.66 fold), Prkcb (2.55 fold) and Traf2 (2.14 fold) were up-regulated in the Pkd1-/- cystic kidneys, suggesting a situation where limitation of intracellular Ca2+ could promote cAMP mediated activation of B-Raf/MEK/ERK pathway and cellular proliferation [39-41].