Fig. 3: Loss of Rptor does not disrupt saccule formation.

a, b Whole-lung imaging of dissected lungs from Shh^Cre/+; ROSA26^mTmG/+ (control) and Rptor^f/f; Shh^Cre/+; ROSA26^mTmG/+ mice at 16.5 and 18.5 days post coitus (dpc). GFP was activated from the ROSA26^mTmG allele in all lung epithelial cells by Shh^Cre; tdTomato marked all non-epithelial cells. Many GFP⁺ dots were present on the surface of Rptor^f/f; Shh^Cre/+; ROSA26^mTmG/+ lungs. Scale bar = 1 mm. c Higher magnification of whole-lung imaging and whole-mount immunostaining of dissected lungs from Shh^Cre/+; ROSA26^mTmG/+ and Rptor^f/f; Shh^Cre/+; ROSA26^mTmG/+ mice at 16.5 dpc. GFP and E-Cadherin (E-Cad) labeled all epithelial cells, while SPC (SFTPC) marked alveolar epithelial type II (AT2) cells located at the tips of saccules. Many GFP⁺ dots and patches were found on the surface of Rptor^f/f; Shh^Cre/+; ROSA26^mTmG/+ lungs at 16.5 dpc. SPC distribution in saccule-like structures in Rptor^f/f; Shh^Cre/+; ROSA26^mTmG/+ lungs was similar to that in control lungs at 16.5 dpc. Scale bar = 25 μm. d Higher magnification of whole-lung imaging and whole-mount immunostaining of dissected lungs from Shh^Cre/+; ROSA26^mTmG/+ and Rptor^f/f; Shh^Cre/+; ROSA26^mTmG/+ mice at 18.5 dpc. GFP and E-Cadherin (E-Cad) labeled all epithelial cells, while SPC marked alveolar epithelial type II (AT2) cells located at the tip of saccules. Developmental progression of SPC distribution from 16.5 to 18.5 dpc followed a similar pattern between control and Rptor-deficient lungs. Scale bar = 25 μm.