Table 3 Key signalling pathways involved in mammalian lung development

Fibroblast Growth Factor (FGF)

Role in the rate of airway bud extension

Involved in the formation of new alveoli

Limits proliferation or migration of branching epithelium

FGF among the signals that confer anterior-posterior identity

Sonic Hedgehog (SHH)

Important in regulating lung cell proliferation and asymmetry

Negatively regulates FGF10

Limits lung bud growth

NK2 homeobox (NKX2.1)

Important in formation of tracheo-oesophageal septum

Essential for initiating branching

Notch

Key role in cell-cell communication during lung development

Promotes proximal lung cell fates

Planar Cell Polarity (PCP)

Drives polarisation of cells

Required for branching

Involved in determining lung architecture

Retinoic Acid

Promotes growth of the primary lung buds

Down-regulates TGF β signalling

Transforming growth factor β/Bone morphogenic protein (BMP)- SMAD (TGFβ/BMP-SMAD)

Can inhibit/stimulate lung morphogenesis

Contributes to distal lung development

BMP among the signal that confer anterior-posterior identity

Wnt/β-catenin

Negatively regulates branching

Involved in developing peripheral airways