title: Localization of protein kinase C isoforms in the optic pathway of mouse embryos and their role in axon routing at the optic chiasm.
abstract: Protein kinase C (PKC) plays a key role in many receptor-mediated signaling pathways that regulate cell growth and development. However, its roles in guiding axon growth and guidance in developing neural pathways are largely unknown. To investigate possible functions of PKC in the growth and guidance of axons in the optic chiasm, we first determined the localization of major PKC isoforms in the retinofugal pathway of mouse embryos, at the stage when axons navigate through the midline. Results showed that PKC was expressed in isoform specific patterns in the pathway. PKC-α immunoreactivity was detected in the chiasm and the optic tract. PKC-βΙΙ was strong in the optic stalk but was attenuated on axons in the diencephalon. Immunostaining for PKC-ε showed a colocalization in the chiasmatic neurons that express a surface antigen stage specific embryonic antigen-1 (SSEA-1). These chiasmatic neurons straddled the midline of the optic chiasm, and have been shown in earlier studies a role in regulation of axon growth and guidance. Expression levels of PKC-βΙ, -δ and -γ were barely detectable in the pathway. Blocking of PKC signaling with Ro-32-0432, an inhibitor specific for PKC-α and -β at nanomolar concentration, produced a dramatic reduction of ipsilateral axons from both nasal retina and temporal crescent. We conclude from these studies that PKC-α and -βΙΙ are the predominant forms in the developing optic pathway, whereas PKC-ε is the major form in the chiasmatic neurons. Furthermore, PKC-α and -βΙΙ are likely involved in signaling pathways triggered by inhibitory molecules at the midline that guide optic axons to the uncrossed pathway.
authors.affiliation: School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China; Department of Neurology, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, Guangdong, China. Electronic address: merrysums@gmail.com.
authors.forename: Liqing
authors.initials: L
authors.lastname: Wang
authors.affiliation: School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China. Electronic address: joyce.lam@cuhk.edu.hk.
authors.forename: Joyce Shi-Ying
authors.initials: JS
authors.lastname: Lam
authors.affiliation: School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China. Electronic address: zhaohui@cuhk.edu.hk.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhao
authors.affiliation: Department of Anatomy and Embryology, School of Basic Medical Sciences, Peking University, Beijing, China. Electronic address: wangjun74008@bjmu.edu.cn.
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.affiliation: School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China. Electronic address: sunonchan@cuhk.edu.hk.
authors.forename: Sun-On
authors.initials: SO
authors.lastname: Chan
mesh_terms: D000818:Animals; D001369:Axons / Q000201:enzymology / Q000502:physiology*; D007527:Isoenzymes / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009897:Optic Chiasm / Q000166:cytology / Q000196:embryology / Q000201:enzymology*; D065866:Optic Tract / Q000166:cytology / Q000196:embryology / Q000201:enzymology; D011493:Protein Kinase C / Q000378:metabolism*; D064546:Protein Kinase C beta / Q000378:metabolism; D051571:Protein Kinase C-alpha / Q000378:metabolism; D051744:Protein Kinase C-epsilon / Q000378:metabolism; D012160:Retina / Q000166:cytology / Q000196:embryology / Q000201:enzymology; D012165:Retinal Ganglion Cells / Q000201:enzymology / Q000502:physiology*; D014795:Visual Pathways / Q000196:embryology* / Q000201:enzymology*
chemical_list: D007527:Isoenzymes; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D051571:Protein Kinase C-alpha; D051744:Protein Kinase C-epsilon
keywords: Chiasm; Development; Optic tract; Retina; Visual pathway