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Identity of neocortical layer 4 neurons is specified through correct positioning into the cortex.

Oishi K, Nakagawa N, Tachikawa K, Sasaki S, Aramaki M, Hirano S, Yamamoto N, Yoshimura Y, Nakajima K - Elife (2016)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy, Keio University School of Medicine, Tokyo, Japan.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus

Morphological changes of “future L4 neurons” induced by knockdown of Pcdh20.(A–C) The remaining cells in Figure 4E–G are presented. (D–F) CONsh (D, F) or PC20sh (E) vector together with a GFP vector was electroporated into E14.0 (D, E) or E15.0 (F) brains, then, P7 brains were fixed and analyzed. The sections were counterstained with PI (magenta). High-magnification images are presented in the insets. The Pcdh20-knockdown cells possessed apical dendrites and axons, which are characteristics of pyramidal neurons in L2/3 of the neocortex. Scale bars, 50 µm (A); 100 µm (D).DOI:http://dx.doi.org/10.7554/eLife.10907.011
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fig4s2: Morphological changes of “future L4 neurons” induced by knockdown of Pcdh20.(A–C) The remaining cells in Figure 4E–G are presented. (D–F) CONsh (D, F) or PC20sh (E) vector together with a GFP vector was electroporated into E14.0 (D, E) or E15.0 (F) brains, then, P7 brains were fixed and analyzed. The sections were counterstained with PI (magenta). High-magnification images are presented in the insets. The Pcdh20-knockdown cells possessed apical dendrites and axons, which are characteristics of pyramidal neurons in L2/3 of the neocortex. Scale bars, 50 µm (A); 100 µm (D).DOI:http://dx.doi.org/10.7554/eLife.10907.011

Mentions: (A–D) CONsh (A, C) or PC20sh (B) vector together with a GFP vector was electroporated into E14.0 (A, B) or E15.0 (C) brains. Fluoro-Gold was injected at P7 into the cortex contralateral to the side of electroporation, then, the P10 brains were fixed and analyzed. The images at low magnification are shown in Figure 4—figure supplement 1. Results of quantitative analyses of A–C are presented in D (n = 4 each group). (E–G) CONsh (E, G) or PC20sh (F) vector together with a GFP vector was electroporated into E14.0 (E, F) or E15.0 (G) brains. The cell morphologies were then analyzed in P14–19 brains by injection of biocytin and sequential visualization with avidin-Cy3. The remaining cells are presented in Figure 4—figure supplement 2A–C. Pcdh20-knockdown neurons possessed thick apical dendrites, a characteristic morphologic feature of L2/3 neurons, but not of L4 neurons. (H) Effects on electrophysiological properties by Pcdh20 knockdown. Experiments were performed as described in E–G, and the electrophysiological properties were analyzed at P14-19. *p < 0.05 (compared with the Pcdh20-knockdown brains electroporated on E14.0), **p < 0.005, ***p = 0.0204 (compared with the control brains electroporated on E14.0). Scale bars, 50 µm (A, E).


Identity of neocortical layer 4 neurons is specified through correct positioning into the cortex.

Oishi K, Nakagawa N, Tachikawa K, Sasaki S, Aramaki M, Hirano S, Yamamoto N, Yoshimura Y, Nakajima K - Elife (2016)

Morphological changes of “future L4 neurons” induced by knockdown of Pcdh20.(A–C) The remaining cells in Figure 4E–G are presented. (D–F) CONsh (D, F) or PC20sh (E) vector together with a GFP vector was electroporated into E14.0 (D, E) or E15.0 (F) brains, then, P7 brains were fixed and analyzed. The sections were counterstained with PI (magenta). High-magnification images are presented in the insets. The Pcdh20-knockdown cells possessed apical dendrites and axons, which are characteristics of pyramidal neurons in L2/3 of the neocortex. Scale bars, 50 µm (A); 100 µm (D).DOI:http://dx.doi.org/10.7554/eLife.10907.011
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4764574&req=5

fig4s2: Morphological changes of “future L4 neurons” induced by knockdown of Pcdh20.(A–C) The remaining cells in Figure 4E–G are presented. (D–F) CONsh (D, F) or PC20sh (E) vector together with a GFP vector was electroporated into E14.0 (D, E) or E15.0 (F) brains, then, P7 brains were fixed and analyzed. The sections were counterstained with PI (magenta). High-magnification images are presented in the insets. The Pcdh20-knockdown cells possessed apical dendrites and axons, which are characteristics of pyramidal neurons in L2/3 of the neocortex. Scale bars, 50 µm (A); 100 µm (D).DOI:http://dx.doi.org/10.7554/eLife.10907.011
Mentions: (A–D) CONsh (A, C) or PC20sh (B) vector together with a GFP vector was electroporated into E14.0 (A, B) or E15.0 (C) brains. Fluoro-Gold was injected at P7 into the cortex contralateral to the side of electroporation, then, the P10 brains were fixed and analyzed. The images at low magnification are shown in Figure 4—figure supplement 1. Results of quantitative analyses of A–C are presented in D (n = 4 each group). (E–G) CONsh (E, G) or PC20sh (F) vector together with a GFP vector was electroporated into E14.0 (E, F) or E15.0 (G) brains. The cell morphologies were then analyzed in P14–19 brains by injection of biocytin and sequential visualization with avidin-Cy3. The remaining cells are presented in Figure 4—figure supplement 2A–C. Pcdh20-knockdown neurons possessed thick apical dendrites, a characteristic morphologic feature of L2/3 neurons, but not of L4 neurons. (H) Effects on electrophysiological properties by Pcdh20 knockdown. Experiments were performed as described in E–G, and the electrophysiological properties were analyzed at P14-19. *p < 0.05 (compared with the Pcdh20-knockdown brains electroporated on E14.0), **p < 0.005, ***p = 0.0204 (compared with the control brains electroporated on E14.0). Scale bars, 50 µm (A, E).

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy, Keio University School of Medicine, Tokyo, Japan.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus