While decreases in first-phase insulin secretion are also a hallmark of preclinical T1D (Daneman 2006; Sosenko, Skyler et al., 2013), it is unknown whether changes in Cx36 gap junction coupling and Ca2+ signaling dynamics also occur early in the progression of T1D, when islet dysfunction is observed. Here, GJD2 is linked to type 1 diabetes mellitus.