Rescuing lung development through embryonic inhibition of histone acetylation.

A major barrier to the impact of genomic diagnosis in patients with congenital malformations is the lack of understanding regarding how sequence variants contribute to disease pathogenesis and whether this information could be used to generate patient-specific therapies. Congenital diaphragmatic hernia (CDH) is among the most common and severe of all structural malformations; however, its underlying mechanisms are unclear. We identified loss-of-function sequence variants in the epigenomic regulator gene SIN3A in two patients with complex CDH. Tissue-specific deletion of Sin3a in mice resulted in defects in diaphragm development, lung hypoplasia, and pulmonary hypertension, the cardinal features of CDH and major causes of CDH-associated mortality. Loss of SIN3A in the lung mesenchyme resulted in reduced cellular differentiation, impaired cell proliferation, and increased DNA damage. Treatment of embryonic Sin3a mutant mice with anacardic acid, an inhibitor of histone acetyltransferase, reduced DNA damage, increased cell proliferation and differentiation, improved lung and pulmonary vascular development, and reduced pulmonary hypertension. These findings demonstrate that restoring the balance of histone acetylation can improve lung development in the Sin3a mouse model of CDH.

PBX transcription factors drive pulmonary vascular adaptation to birth.

A critical event in the adaptation to extrauterine life is relaxation of the pulmonary vasculature at birth, allowing for a rapid increase in pulmonary blood flow that is essential for efficient gas exchange. Failure of this transition leads to pulmonary hypertension (PH), a major cause of newborn mortality associated with preterm birth, infection, hypoxia, and malformations including congenital diaphragmatic hernia (CDH). While individual vasoconstrictor and dilator genes have been identified, the coordination of their expression is not well understood. Here, we found that lung mesenchyme-specific deletion of CDH-implicated genes encoding pre-B cell leukemia transcription factors (Pbx) led to lethal PH in mice shortly after birth. Loss of Pbx genes resulted in the misexpression of both vasoconstrictors and vasodilators in multiple pathways that converge to increase phosphorylation of myosin in vascular smooth muscle (VSM) cells, causing persistent constriction. While targeting endothelin and angiotensin, which are upstream regulators that promote VSM contraction, was not effective, treatment with the Rho-kinase inhibitor Y-27632 reduced vessel constriction and PH in Pbx-mutant mice. These results demonstrate a lung-intrinsic, herniation-independent cause of PH in CDH. More broadly, our findings indicate that neonatal PH can result from perturbation of multiple pathways and suggest that targeting the downstream common effectors may be a more effective treatment for neonatal PH.

Pulmonary neuroendocrine cells function as airway sensors to control lung immune response.

The lung is constantly exposed to environmental atmospheric cues. How it senses and responds to these cues is poorly defined. Here, we show that Roundabout receptor (Robo) genes are expressed in pulmonary neuroendocrine cells (PNECs), a rare, innervated epithelial population. Robo inactivation in mouse lung results in an inability of PNECs to cluster into sensory organoids and triggers increased neuropeptide production upon exposure to air. Excess neuropeptides lead to an increase in immune infiltrates, which in turn remodel the matrix and irreversibly simplify the alveoli. We demonstrate in vivo that PNECs act as precise airway sensors that elicit immune responses via neuropeptides. These findings suggest that the PNEC and neuropeptide abnormalities documented in a wide array of pulmonary diseases may profoundly affect symptoms and progression.