KCNJ11 and congenital isolated hyperinsulinism: Studies utilizing naturally occurring TMD0 mutations present in patients with CHI have identified residues which may be crucial for folding or subunit interactions (Chan et al., 2003; Yan et al., 2004, 2007; Pratt et al., 2011), but the precise nature of the interface of TMD0 with Kir6.2 remains to be elucidated.