title: Specific labeling of climbing fibers shows early synaptic interactions with immature Purkinje cells in the prenatal cerebellum.
abstract: During development, growing axons must locate target cells to form synapses. This is not easy, since target cells are also growing and even actively migrating. In some brain regions, such axons have been reported to wait for the timing when target cells become mature, without invading their target region. However, in the cerebellum climbing fibers (CFs), major afferent axons, arrive near their target neurons, Purkinje cells, when the neurons are still actively migrating. We, therefore, examined whether synaptic contacts are established at such early stages. To specifically label CFs, we introduced by in utero electroporation a mixture of genes encoding for Ptf1a-enhancer-driven Cre recombinase and Cre-dependent fluorescent protein into the mouse hindbrain at embryonic day (E) 10.5 and observed them during development. The earliest stages at which labeled CFs were observed in the cerebellar primordium were E15.5-E16.5. These fibers were fasciculated in the dorsal region and entered the cerebellar primordium. Some fibers defasciculated and reached the caudal region. At E17.5 and E18.5, fasciculated fibers were also found in the mantle region, and some grew toward the surface of the primordium to penetrate a mass of Purkinje cells. Interestingly, as early as E16.5, labeled fibers were found to run in close apposition to Purkinje cell dendrites and to express a presynaptic marker. These observations suggest that CFs form synapses with Purkinje cells as soon as the fibers enter the cerebellum.
authors.affiliation: Laboratory of Neuroscience, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, 565-0871, Japan.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Kita
authors.affiliation: Laboratory of Neuroscience, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, 565-0871, Japan.
authors.forename: Kazuto
authors.initials: K
authors.lastname: Tanaka
authors.affiliation: Laboratory of Neuroscience, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, 565-0871, Japan.
authors.forename: Fujio
authors.initials: F
authors.lastname: Murakami
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism; D002531:Cerebellum / Q000166:cytology* / Q000196:embryology* / Q000378:metabolism; D018274:Electroporation; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D007150:Immunohistochemistry; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D011689:Purkinje Cells / Q000166:cytology* / Q000378:metabolism; D013569:Synapses / Q000378:metabolism; D016708:Synaptophysin / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D000097573:Red Fluorescent Protein
chemical_list: D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D016708:Synaptophysin; D014157:Transcription Factors; D000097573:Red Fluorescent Protein; C569015:Syp protein, mouse; C485184:enhanced green fluorescent protein; C062602:transcription factor PTF1
keywords: Purkinje cell; cerebellum; climbing fiber; in utero electroporation; synaptic contact