YAP1 and obstructive sleep apnea syndrome: To first determine the presence of both TGFβ receptors, as well as the degree of Smad activation in response to exogenous TGFβ and its effects on Hippo pathway mediators, TAZ and YAP, immunoblotting analyses was completed on four canine OSA cell lines, two derived from primary tumours (OVC-cOSA-75 and OVC-cOSA-78), and two derived from metastatic colonies (OVC-cOSA-31 and D17).