ROBO1 and congenital diaphragmatic hernia: Sui et al. (2018) demonstrated that PNECs are essential for allergen-induced asthma-like responses in mice. Ascl1 knockout mice, which lack PNECs, showed a blunted mucosal type 2 response (Box 1) after ovalbumin allergen challenge, which could be rescued by the intratracheal administration of CGRP and GABA (Branchfield et al., 2016). In addition, Branchfield et al. (2016) showed that upregulation of PNEC products in Robo1 and Robo2 double-mutant mice, a genetic model of congenital diaphragmatic hernia, increased immune responses and airway inflammation.