Heterotrimeric Gi proteins are crucial modulators of G protein-coupled receptor signaling, with Gαi2 ubiquitously expressed and implicated in diverse physiological processes. Previous reports described partial lethality in Gnai2-deficient mice, but the timing and mechanism of death remained unclear. Here, we demonstrate that impaired neonatal respiratory adaptation contributes to mortality in Gnai2-deficient neonates. Despite normal Mendelian distribution at birth and no overt malformations, at least 20% of the expected Gnai2-deficient neonates died within minutes after birth, displaying abnormal breathing, cyanosis, and features resembling neonatal respiratory distress syndrome (RDS). Histological and ultrastructural analyses revealed reduced alveolar surface area, thickened septa, increased mesenchymal tissue, and impaired surfactant ultrastructure, despite unaltered alveolar surfactant phospholipid levels. These findings suggest that Gαi2 modulates the structural deployment and functional organization of surfactant within alveoli, although the incomplete phenotype and survival of some neonates indicate a regulatory rather than indispensable role of Gαi2. Our data underscore the complexity of neonatal respiratory adaptation and highlight potential systemic and intercellular mechanisms underlying alveolar stabilization.
Keywords: Gαi-signaling; Gαi2; lung development; neonatal lethality; respiratory distress syndrome (RDS); surfactant.