Figure 1

Immunostaining revealed distinct patterns of α ₅ expression in the lung during organogenesis. A. α₅ was expressed at E13.5 in primitive airway epithelium (arrow) and sporadically in pulmonary mesenchyme (arrowhead). B and C. During the late pseudoglandular period of development (B, E15.5) and early saccular stage of development (C, E17.5), α₅ continued to localize to pulmonary epithelium (arrows). D. At E18.5, α₅ expression was detected in larger airways (arrows) as well as in primitive respiratory epithelium (arrowhead). E. At PN1, α₅ expression was markedly detected in proximal lung airways (arrow) and only minimally detected in the peripheral lung (arrowhead). F. At the commencement of alveologenesis (PN4), α₅ localized to lung parenchyma (arrow) and was noticeably absent in the airways (arrowhead). G. At PN10, α₅ expression persisted in the respiratory compartment (arrow). H. After alveologenesis progressed to PN20, α₅ was abundantly expressed throughout the lung, being detected in proximal (arrow) as well as distal pulmonary epithelium (arrowhead). I. PN20 sections incubated without primary α₅ antibody revealed no immunoreactivity. Six mice were included in each group and representative images at 40× magnification are shown.