GCG and type 1 diabetes mellitus: In spite of severe technical restrictions, the importance of α-cell in islet biology, pathobiology and implication on cell replacement therapy of T1D have been the impetus of the vigorous thrust of key labs to examine the intimate cross-talk between islet cells (Ishihara et al., 2003), α-cell glucose-sensing (Heimberg et al., 1996), α-cell ion channels (Kanno et al., 2002), and glucagon exocytosis (Barg, 2003) not only in rodent models, but also in human α-cells (MacDonald et al., 2007; Rorsman et al., 2008).