aDepartment of Otolaryngology – Head and Neck Surgery, The Ohio State University, Columbus, Ohio

bUpper Airway Biology Laboratory, Department of Medicine, University of California, San Francisco, California, USA

Correspondence to Kai Zhao, PhD, Department of Otolaryngology – Head and Neck Surgery, The Ohio State University, 915 Olentangy River Road, Columbus, OH 43212, USA. Tel: +1 614 293 3857; fax: +1 614 293 7292; e-mail: [email protected]