PDPN and bronchopulmonary dysplasia: Immunohistochemistry analysis confirmed the abundant expression of the human SRY (Fig. 3A, top right) and presence of type I and II alveolar epithelial cells (AECs), as indicated by immunostaining of T1α and surfactant protein C respectively58, 59 (Fig. 3A, middle and bottom), suggesting that ectopic SRY expression in the developing lung retarded its postnatal alveologenesis and promoted bronchopulmonary dysplasia, likely resulting in deficiency in alveolar airspace, decrease in gas exchange efficiency, and impairment of respiratory functions57.