CA2 and Alzheimer disease: In postmortem human AD brain specimens and rodent models of AD, reactive astrocytes exhibit signs of Ca2+ dysregulation (Kuchibhotla et al., 2009) or hyperactivation of key signaling mediators including the Ca2+/calmodulin-dependent protein phosphatase calcineurin (CN) and the CN-dependent transcription factor nuclear factor of activated T cells (NFAT; Norris et al., 2005; Abdul et al., 2009; Lim et al., 2013; Pleiss et al., 2016; Sompol et al., 2017).