title: APC2 plays an essential role in axonal projections through the regulation of microtubule stability.
abstract: Growth cones at the tip of growing axons are key cellular structures that detect guidance cues and mediate axonal growth. An increasing number of studies have suggested that the dynamic regulation of microtubules in the growth cone plays an essential role in growth cone steering. The dynamic properties of microtubules are considered to be regulated by variegated cellular factors but, in particular, through microtubule-interacting proteins. Here, we examined the functional role of adenomatous polyposis coli-like molecule 2 (APC2) in the development of axonal projections by using the chick retinotectal topographic projection system. APC2 is preferentially expressed in the nervous system from early developmental stages through to adulthood. Immunohistochemical analysis revealed that APC2 is distributed along microtubules in growth cones as well as axon shafts of retinal axons. Overexpression of APC2 in cultured cells induced the stabilization of microtubules, whereas the knockdown of APC2 in chick retinas with specific short hairpin RNA reduced the stability of microtubules in retinal axons. APC2 knockdown retinal axons showed abnormal growth attributable to a reduced response to ephrin-A2 in vitro. Furthermore, they showed drastic alterations in retinotectal projections without making clear target zones in the tectum in vivo. These results suggest that APC2 plays a critical role in the development of the nervous system through the regulation of microtubule stability.
authors.affiliation: Division of Molecular Neurobiology, National Institute for Basic Biology, Okazaki 444-8787, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Shintani
authors.forename: Masaru
authors.initials: M
authors.lastname: Ihara
authors.forename: Sachiko
authors.initials: S
authors.lastname: Tani
authors.forename: Juichi
authors.initials: J
authors.lastname: Sakuraba
authors.forename: Hiraki
authors.initials: H
authors.lastname: Sakuta
authors.forename: Masaharu
authors.initials: M
authors.lastname: Noda
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001369:Axons / Q000502:physiology*; D002460:Cell Line; D002465:Cell Movement / Q000502:physiology; D002642:Chick Embryo; D003598:Cytoskeletal Proteins / Q000172:deficiency / Q000502:physiology*; D018274:Electroporation / Q000379:methods; D036383:Ephrin-A2; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000235:genetics; D020439:Growth Cones / Q000502:physiology*; D006801:Humans; D008870:Microtubules / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000502:physiology; D012160:Retina / Q000166:cytology / Q000196:embryology; D014162:Transfection / Q000379:methods; D014404:Tubulin / Q000378:metabolism; D014795:Visual Pathways / Q000196:embryology / Q000378:metabolism
chemical_list: D003598:Cytoskeletal Proteins; D036383:Ephrin-A2; C498585:TUBB3 protein, human; D014404:Tubulin; C117846:adenomatous polyposis coli protein 2; D049452:Green Fluorescent Proteins