For example, animals that overexpress MUC5AC or MUC5B in the lungs do not produce airway obstructions or inflammation, even when in some cases the amount of mucus protein is almost 20 times higher than that in control animals, thus reaffirming the idea that under normal fluid transport the amount of mucus is not an issue (44, 45). The gene discussed is MUC5B; the disease is Airway obstruction.