Chromatin remodeler Znhit1 controls bone morphogenetic protein signaling in embryonic lung tissue branching.

Branching morphogenesis is a key process essential for lung and other organ development in which cellular and tissue architecture branch out to maximize surface area. While this process is known to be regulated by differential gene expression of ligands and receptors, how chromatin remodeling regulates this process remains unclear. Znhit1 (zinc finger HIT-type containing 1), acting as a chromatin remodeler, has previously been shown to control the deposition of the histone variant H2A.Z. Here, we demonstrate that Znhit1 also plays an important role in regulating lung branching. Using Znhit1 conditional KO mice, we show that Znhit1 deficiency in the embryonic lung epithelium leads to failure of branching morphogenesis and neonatal lethality, which is accompanied by reduced cell proliferation and increased cell apoptosis of the epithelium. The results from the transcriptome and the chromatin immunoprecipitation assay reveal that this is partially regulated by the derepression of Bmp4, encoding bone morphogenetic protein (BMP) 4, which is a direct target of H2A.Z. Furthermore, we show that inhibition of BMP signaling by the protein inhibitor Noggin rescues the lung branching defects of Znhit1 mutants ex vivo. Taken together, our study identifies the critical role of Znhit1/H2A.Z in embryonic lung morphogenesis via the regulation of BMP signaling.