Mechanisms of Proximal-Distal Patterning of the Lung: A review of: Lu MM, Yang H, Zhang L, et al. 2001 The bone morphogenetic protein antagonist gremlin regulates proximal-distal patterning of the lung. Develop Dyn 222:667???680; and Yang H, Lu MM, Zhang L, et al. 2002 GATA6 regulates differentiation of distal lung epithelium. Development 129:2233???2246