Fig. 4. Foxp2^-/-;Foxp1^+/- compound mutants exhibit dramatic defects in lung airway morphogenesis. Foxp2^-/-;Foxp1^+/- compound mutants were generated by crossing Foxp1^+/-;Foxp2^+/- double heterozygous mice to Foxp1^+/- mice. (A-D) Overall lung size was reduced at both E14.5 and E18.5 in Foxp2^-/-;Foxp1^+/- mutants. (E-J) At E14.5, E16.5 and E18.5, significant defects were observed in airway development including decreased branching morphogenesis as demonstrated by the dilated nature of the developing airways. (K) Distal airspace area, as measured using ImageJ software, was significantly increased in Foxp2^-/-;Foxp1^+/- lungs at both E14.5 and E18.5. (L-Q) Despite these defects, proximal-distal epithelial patterning was maintained in Foxp2^-/-;Foxp1^+/- compound mutants as determined by normal expression patterns of SP-C (L,O), CC10 (M,P) and ß-tubulin IV (N,Q) proteins. Scale bars: 500 µm in A-J,L,M,O,P; 100 µm in N,Q.