Lee Hyunwook, Jaquish Abigail, Fernandes Sharlene, Zhao Barbara, Elitz Amber, Cook Kathleen, Trovillion Sarah, Bottasso-Arias Natalia, Han Simon J Y, Goodwin Samantha, Russell Nicholas X, Zacharias Amanda L, Brugmann Samantha A, Whitsett Jeffrey A, Sinner Debora, Sun Xin, Swarr Daniel T, Zacharias William J
Perinatal Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
Division of Pulmonary Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
bioRxiv. 2025 Jun 5:2025.06.02.657302. doi: 10.1101/2025.06.02.657302.
Development of the mammalian lung requires formation of a definitive lung bud from the foregut endoderm, branching morphogenesis, specification of a proximal to distal axis, and differentiation of extensive specialized airway and alveolar epithelial lineages. These steps require coordinated temporal and regional gene expression to define the lung epithelium in preparation for the first breath at birth. While the transcriptional and signaling regulators required for lung development are increasingly well known, the key epigenetic complexes that interact with lineage transcription factors for cell-specific control of gene expression remain to be defined. Here, we identify a key role for the canonical BAF complex, an ATP-dependent chromatin remodeling complex, during lung epithelial development. Loss of canonical BAF activity throughout the foregut endoderm leads to complete failure of lung formation, and selective deletion of a single key subunit, ARID1A, leads to failure of proximal-distal axis specification, with dilated airway-like structures lined by ectopic basal cells found throughout the distal lung, and failure of specification of alveolar type 1 (AT1) cells in the distal saccular epithelium. In place of AT1 cells, we identified a highly proliferative epithelial cell state defined by joint activation of YAP and WNT signaling and loss of BMP signaling response, leading to increased proliferation and failure of appropriate epithelial differentiation. These changes resulted in secondary failure of mesenchymal and endothelial specification, leading to broad loss of patterning of the distal lung further disrupting peripheral lung morphogenesis. Using embryonic lung organoids, we demonstrate that exogenous BMP4 signaling is sufficient to rescue AT1 and AT2 cell differentiation in ARID1A-null epithelium, while WNT and YAP signaling require functional BAF complex. Together, these data demonstrate a requirement for the BAF complex for lung formation, proximal-distal patterning, and cell fate acquisition, and reveal surprising differential specificity between signaling pathways during lung development.
哺乳动物肺的发育需要从前肠内胚层形成确定的肺芽、分支形态发生、近端到远端轴的特化以及广泛的特化气道和肺泡上皮谱系的分化。这些步骤需要协调的时间和区域基因表达来定义肺上皮，为出生时的第一次呼吸做准备。虽然肺发育所需的转录和信号调节因子越来越为人所知，但与谱系转录因子相互作用以实现基因表达的细胞特异性控制的关键表观遗传复合物仍有待确定。在这里，我们确定了经典BAF复合物（一种ATP依赖性染色质重塑复合物）在肺上皮发育过程中的关键作用。前肠内胚层中经典BAF活性的丧失导致肺形成完全失败，而单个关键亚基ARID1A的选择性缺失导致近端到远端轴特化失败，远端肺中出现由异位基底细胞排列的扩张气道样结构，以及远端囊状上皮中1型肺泡（AT1）细胞特化失败。代替AT1细胞，我们确定了一种高度增殖的上皮细胞状态，其特征是YAP和WNT信号的联合激活以及BMP信号反应的丧失，导致增殖增加和适当的上皮分化失败。这些变化导致间充质和内皮特化的继发性失败，导致远端肺模式广泛丧失，进一步破坏外周肺形态发生。使用胚胎肺类器官，我们证明外源性BMP4信号足以挽救ARID1A缺失上皮中的AT1和AT2细胞分化，而WNT和YAP信号需要功能性BAF复合物。总之，这些数据证明了BAF复合物对肺形成、近端到远端模式形成和细胞命运获得的需求，并揭示了肺发育过程中信号通路之间令人惊讶的差异特异性。
