Cranial neural crest cells are a multipotent cell population that generate all the elements of the pharyngeal cartilage with differentiation into chondrocytes tightly regulated by temporal intracellular and extracellular cues. Here, we demonstrate a novel role for miR-27, a highly enriched microRNA in the pharyngeal arches, as a positive regulator of chondrogenesis. Knock down of miR-27 led to nearly complete loss of pharyngeal cartilage by attenuating proliferation and blocking differentiation of pre-chondrogenic cells. Focal adhesion kinase (FAK) is a key regulator in integrin-mediated extracellular matrix (ECM) adhesion and has been proposed to function as a negative regulator of chondrogenesis. We show that FAK is downregulated in the pharyngeal arches during chondrogenesis and is a direct target of miR-27. Suppressing the accumulation of FAK in miR-27 morphants partially rescued the severe pharyngeal cartilage defects observed upon knock down of miR-27. These data support a crucial role for miR-27 in promoting chondrogenic differentiation in the pharyngeal arches through regulation of FAK.
Keywords: Chondrogenesis; Focal adhesion kinase; Pharyngeal arches; Zebrafish; miR-27.
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