Identity of neocortical layer 4 neurons is specified through correct positioning into the cortex
Koji Oishi,
Nao Nakagawa,
Kashiko Tachikawa,
Shinji Sasaki,
Michihiko Aramaki,
Shinji Hirano,
Nobuhiko Yamamoto,
Yumiko Yoshimura,
Kazunori Nakajima
Affiliations
Koji Oishi
Department of Anatomy, Keio University School of Medicine, Tokyo, Japan
Nao Nakagawa
Division of Visual Information Processing, National Institute for Physiological Sciences, National Institutes for Natural Sciences, Okazaki, Japan; Department of Physiological Sciences, Graduate University for Advanced Studies, Okazaki, Japan
Kashiko Tachikawa
Department of Anatomy, Keio University School of Medicine, Tokyo, Japan
Shinji Sasaki
Department of Anatomy, Keio University School of Medicine, Tokyo, Japan
Michihiko Aramaki
Department of Anatomy, Keio University School of Medicine, Tokyo, Japan
Shinji Hirano
Department of Cell Biology, Kansai Medical University, Osaka, Japan
Nobuhiko Yamamoto
Laboratory of Cellular and Molecular Neurobiology, Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
Yumiko Yoshimura
Division of Visual Information Processing, National Institute for Physiological Sciences, National Institutes for Natural Sciences, Okazaki, Japan; Department of Physiological Sciences, Graduate University for Advanced Studies, Okazaki, Japan
Many cell-intrinsic mechanisms have been shown to regulate neuronal subtype specification in the mammalian neocortex. However, how much cell environment is crucial for subtype determination still remained unclear. Here, we show that knockdown of Protocadherin20 (Pcdh20), which is expressed in post-migratory neurons of layer 4 (L4) lineage, caused the cells to localize in L2/3. The ectopically positioned “future L4 neurons” lost their L4 characteristics but acquired L2/3 characteristics. Knockdown of a cytoskeletal protein in the future L4 neurons, which caused random disruption of positioning, also showed that those accidentally located in L4 acquired the L4 characteristics. Moreover, restoration of positioning of the Pcdh20-knockdown neurons into L4 rescued the specification failure. We further suggest that the thalamocortical axons provide a positional cue to specify L4 identity. These results suggest that the L4 identity is not completely determined at the time of birth but ensured by the surrounding environment after appropriate positioning.
