Gene expression changes in the respiratory epithelium of miR-34/449 knockout mice

MicroRNA ablation prevents multiciliogenesis via cell cycle deregulation MicroRNAs (miRNAs) have been implicated in various biological processes but have been most frequently described to inhibit proliferation and tumorigenesis. Here we describe an essential function of the miR-34/449 family during differentiation of multiciliated cells that is mediated by their well-described suppression of cell cycle progression. Constitutive deletion of all six members of this miRNA family triggers a derepression of multiple cell cycle-promoting proteins, thereby preventing epithelial cells from exiting the cell cycle and to maintain in a quiescent state. As a result, formation of motile multicilia is strongly inhibited in several tissues including the respiratory epithelium and the fallopian tube. Consequently, mice lacking miR-34/449 genes display infertility as well as severe chronic airway disease leading to postnatal death. These results show how miRNA-mediated repression of the cell cycle is required to allow multiciliogenesis to proceed during epithelial differentiation. We analyzed samples from the respiratory epithelium of the nose (NRE) of 5 wild-type (WT) and 5 miR-34/449 triple knockout (TKO) embryos (at E16.5), which were isolated using Laser Capture Microdissection (LCM).