1. Department of Human Anatomy; Guangzhou Medical University; Guangzhou; Guangdong; People's Republic of China
2. Department of Histology and Embryology; Guangzhou Medical University; Guangzhou; People's Republic of China
3. Stanley Ho Centre for Emerging Infectious Diseases, Chinese University of Hong Kong; Shatin; Hong Kong
4. Department of Cell Biology and Anatomy; School of Medicine, University of South Carolina; Columbia; SC