Interestingly, regions of airways exhibiting enhanced eGFP expression were detected close to the tips of airway branch-points in close proximity to neuro-epithelial bodies (NEBs). Analysis of the eGFP expression in relation to CC10 and CGRP, a differentiation marker of neuro-epithelial cells, revealed that eGFP pos -CC10 low cells formed ''caps'' over clusters of CGRP pos cells. From E19.5, the eGFP pos -CC10 low ''cap'' cells (green-arrows in Figure 4B ) were separated from the eGFP neg -CC10 pos cells by a zone of double positive epithelial cells (yellow-arrows in Figure 4B) . Notably, the zone of eGFP pos -CC10 pos cells coincided with zones richin NEBs ( Figure S5 ). From P15 and beyond, the only NEBassociated eGFP pos cells were CGRP pos neuro-epithelial cells (blue-arrows in Figure 4B ).