PROJECT SUMMARY Neuroendocrine Cell Hyperplasia of Infancy (NEHI) is a rare pediatric lung disease characterized by chronic tachypnea, low blood oxygen saturation requiring supplemental oxygen, and often failure to thrive. A defining pathological feature of NEHI is the observed increase of pulmonary neuroendocrine cells in lung biopsies. However, it is unknown if this increase, or other genetic or environmental factors cause the disease. Mimicking an NKX2.1 point mutation identified in NEHI patients, we engineered the first animal model of NEHI in mice carrying this patient mutation. Our preliminary data indicate that this model recapitulates key features of the disease. We will use this model as an entry point to address key clinical questions associated with NEHI pathogenesis. As there is no particular therapy for NEHI beyond supportive care, our findings may inform specific pharmacological therapy targeting the key NEHI disease causal factors.