title: Cortical Divergent Projections in Mice Originate from Two Sequentially Generated, Distinct Populations of Excitatory Cortical Neurons with Different Initial Axonal Outgrowth Characteristics.
abstract: Excitatory cortical neurons project to various subcortical and intracortical regions, and exhibit diversity in their axonal connections. Although this diversity may develop from primary axons, how many types of axons initially occur remains unknown. Using a sparse-labeling in utero electroporation method, we investigated the axonal outgrowth of these neurons in mice and correlated the data with axonal projections in adults. Examination of lateral cortex neurons labeled during the main period of cortical neurogenesis (E11.5-E15.5) indicated that axonal outgrowth commonly occurs in the intermediate zone. Conversely, the axonal direction varied; neurons labeled before E12.5 and the earliest cortical plate neurons labeled at E12.5 projected laterally, whereas neurons labeled thereafter projected medially. The expression of Ctip2 and Satb2 and the layer destinations of these neurons support the view that lateral and medial projection neurons are groups of prospective subcortical and callosal projection neurons, respectively. Consistently, birthdating experiments demonstrated that presumptive lateral projection neurons were generated earlier than medial projection neurons, even within the same layer. These results suggest that the divergent axonal connections of excitatory cortical neurons begin from two types of primary axons, which originate from two sequentially generated distinct subpopulations: early-born lateral (subcortical) and later-born medial (callosal) projection neuron groups.
authors.affiliation: Division of Cerebral Circuitry, National Institute for Physiological Sciences, Myodaiji, Okazaki, Aichi 444-8787, Japan.|Japan Science and Technology Agency, Core Research for Evolutional Science and Technology, Tokyo 102-0076, Japan.|Graduate School of Biological Sciences, Nara Institute of Science and Technology, Takayama-cho, Ikoma, Nara 630-0192, Japan.
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Hatanaka
authors.affiliation: Graduate School of Biological Sciences, Nara Institute of Science and Technology, Takayama-cho, Ikoma, Nara 630-0192, Japan.|Current addresses: Division of Developmental Neurobiology, Kobe University Graduate School of Medicine, Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Namikawa
authors.affiliation: Laboratory of Neuroscience, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0178, Japan.|Division of Brain Function, National Institute of Genetics, Yata, Mishima, Shizuoka 411-8540, Japan.
authors.forename: Kenta
authors.initials: K
authors.lastname: Yamauchi
authors.affiliation: Division of Cerebral Circuitry, National Institute for Physiological Sciences, Myodaiji, Okazaki, Aichi 444-8787, Japan.|Japan Science and Technology Agency, Core Research for Evolutional Science and Technology, Tokyo 102-0076, Japan.|Department of Physiological Sciences, Graduate University for Advanced Studies (SOKENDAI), Okazaki, Aichi 444-8787, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Kawaguchi
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology*; D002540:Cerebral Cortex / Q000196:embryology* / Q000378:metabolism / Q000502:physiology*; D018274:Electroporation; D036961:Matrix Attachment Region Binding Proteins / Q000378:metabolism; D051379:Mice; D009434:Neural Pathways / Q000196:embryology / Q000378:metabolism / Q000502:physiology; D055495:Neurogenesis; D009474:Neurons / Q000378:metabolism / Q000502:physiology*; D012097:Repressor Proteins; D014157:Transcription Factors / Q000378:metabolism; D025521:Tumor Suppressor Proteins
chemical_list: C511143:Bcl11b protein, mouse; D036961:Matrix Attachment Region Binding Proteins; D012097:Repressor Proteins; C501473:SATB2 protein, mouse; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins
keywords: birthdate; callosal projection neuron; electroporation; laminar fate; subcortical projection neuron