Figure 3. miR‐34a‐5p acts in PDGFRα⁺ cells to block lung alveolarization.

• A
  In silico identification of miR‐34a binding sites in the Pdgfra 3′‐UTR.
• B
  Immunoblot detection of PDGFRα levels in MLg cells after treatment with scrambled microRNA (SCR) or a miR‐34a (MIM34a) mimic (n = 3 separate cell cultures for each group).
• C
  Quantitative RT–PCR detection of miR‐34a/b/c‐5p levels in MLg cells in vitro, maintained under 21% O₂ or 85% O₂ (n = 3 separate cell cultures for each group).
• D
  Immunoblot detection of PDGFRα levels in the lungs of mouse pups (n = 6 animals for each group) at post‐natal day (P)5, during normal (21% O₂) and aberrant (85% O₂) alveolarization.
• E
  Immunoblot detection of PDGFRα levels in MLg cells in vitro, maintained under 21% O₂ or 85% O₂, where cells had been transfected wither with a scrambled (SCR) antimiR, or an antimiR directed against miR‐34a (A34a) (n = 3 separate cell cultures for each group).
• F
  Quantitative RT–PCR detection of miR‐34a‐5p levels in PDGFRα⁺ cells, sorted by FACS from the lungs of mouse pups (n = 4 animals for each group; data from an independent repetition are provided in Appendix Fig S5) at P5, maintained under 21% O₂ or 85% O₂ from birth.
• G
  Schematic illustration of the generation of a conditional, inducible deletion‐ready mouse strain, where administration of tamoxifen (Tmxfn) abrogated miR‐34a expression in Pdgfra‐expressing cells (denoted miR‐34a^iΔPC/iΔPC).
• H
  Quantitative RT–PCR detection of miR‐34a‐5p levels in PDGFRα⁺ cells, sorted by FACS from the lungs of either wild‐type (34a^wt/wt) mouse pups, or mouse pups in which miR‐34a expression in Pdgfra‐expressing cells (34a^iΔPC/iΔPC) at P5 (n = 4 animals for each group).
• I
  Qualitative analysis of lung structure in Richardson‐stained plastic‐embedded lung sections from 34a^wt/wt or 34a^iΔPC/iΔPC mouse pups at P14 during aberrant (85% O₂) alveolarization, compared with 34a^iΔPC/iΔPC during normal (21% O₂) alveolarization (scale bar, 50 μm). Data are representative of observations made in four other experiments.
• J
  Quantification of total number of alveoli by design‐based stereology in 34a^wt/wt or 34a^iΔPC/iΔPC mouse pups at P14, during normal and aberrant alveolarization (n = 5 animals for each group).
• K
  Quantification of mean septal thickness by design‐based stereology in 34a^wt/wt or 34a^iΔPC/iΔPC mouse pups at P14, during normal and aberrant alveolarization (n = 5 animals for each group).

Data information: For immunoblots (B, D, E), protein loading equivalence was controlled by βactin levels. (C, F, H, J, K) Data represent mean ± SD. In (C, F, and H), P values for pair‐wise comparisons were calculated by unpaired Student's t‐test. In (J and K), P values for selected comparisons were calculated by one‐way ANOVA with Tukey's post hoc modification.Source data are available online for this figure.