In IEC [25], the essential roles of Jak3 include cytoskeletal remodeling [29], intestinal restitution [30], mucosal homeostasis [31], trans-molecular regulation of adapter protein Shc [32], and a deficiency of its functions leads to predisposition to chronic intestinal inflammation [20] and systemic CLGI-associated obesity [21]. This evidence concerns the gene JAK3 and obesity due to melanocortin 4 receptor deficiency.