GSK3β N-terminus binding to p53 promotes its acetylation

The prevalence in human cancers of mutations in p53 exemplifies its crucial role as a tumor suppressor transcription factor. Previous studies have shown that the constitutively active serine/threonine kinase glycogen synthase kinase-3β (GSK3β) associates with the C-terminal basic domain of p53 and regulates its actions. In this study we identified the GSK3β N-terminal amino acids 78–92 as necessary for its association with p53. Inhibitors of GSK3 impaired the acetylation of p53 at Lys373 and Lys382 near the GSK3β binding region in p53, indicating that GSK3β facilitates p53 acetylation. We also found that acetylation of p53 reduced its association with GSK3β, as well as with GSK3α. These results indicate that the N-terminal region of GSK3β binds p53, this association promotes the acetylation of p53, and subsequently acetylated p53 dissociates from GSK3

APC sets the Wnt tone necessary for cerebral cortical progenitor development

Adenomatous polyposis coli (APC) regulates the activity of β-catenin, an integral component of Wnt signaling. However, the selective role of the APC–β-catenin pathway in cerebral cortical development is unknown. Here we genetically dissected the relative contributions of APC-regulated β-catenin signaling in cortical progenitor development, a necessary early step in cerebral cortical formation. Radial progenitor-specific inactivation of the APC–β-catenin pathway indicates that the maintenance of appropriate β-catenin-mediated Wnt tone is necessary for the orderly differentiation of cortical progenitors and the resultant formation of the cerebral cortex. APC deletion deregulates β-catenin, leads to high Wnt tone, and disrupts Notch1 signaling and primary cilium maintenance necessary for radial progenitor functions. β-Catenin deregulation directly disrupts cilium maintenance and signaling via Tulp3, essential for intraflagellar transport of ciliary signaling receptors. Surprisingly, deletion of β-catenin or inhibition of β-catenin activity in APC-null progenitors rescues the APC-null phenotype. These results reveal that APC-regulated β-catenin activity in cortical progenitors sets the appropriate Wnt tone necessary for normal cerebral cortical development

Direct visualization of microtubules using a genetic tool to analyse radial progenitor-astrocyte continuum in brain

Microtubule cytoskeletal dynamics of cortical progenitors and astroglial cells play critical roles in the emergence of normal functional organization of cerebral cortex and in disease processes such as tumorigenesis. However, tools to efficiently visualize these events are lacking. Here we describe a mouse genetic model to efficiently visualize and analyze radial progenitors, their astroglial progeny, and the microtubule cytoskeleton of these cells in the developing and adult brain. Using this tool, we demonstrate altered microtubule organization and capture dynamics in adenomatous polyposis coli deficient radial progenitors. Further, using multiphoton microscopy, we show the utility of this tool in real-time imaging of astrocytes in living mouse brain and the short- term stable nature of astrocytes in cerebral cortex. Thus, this model will help explore the dynamics of radial progenitor/astrocyte development or dysfunction and the influence of microtubule functions during these events

Cdc42 and Gsk3 modulate the dynamics of radial glial growth, inter-radial glial interactions and polarity in the developing cerebral cortex

Polarized radial glia are crucial to the formation of the cerebral cortex. They serve as neural progenitors and as guides for neuronal placement in the developing cerebral cortex. The maintenance of polarized morphology is essential for radial glial functions, but the extent to which the polarized radial glial scaffold is static or dynamic during corticogenesis remains an open question. The developmental dynamics of radial glial morphology, inter-radial glial interactions during corticogenesis, and the role of the cell polarity complexes in these activities remain undefined. Here, using real-time imaging of cohorts of mouse radial glia cells, we show that the radial glial scaffold, upon which the cortex is constructed, is highly dynamic. Radial glial cells within the scaffold constantly interact with one another. These interactions are mediated by growth cone-like endfeet and filopodia-like protrusions. Polarized expression of the cell polarity regulator Cdc42 in radial glia regulates glial endfeet activities and inter-radial glial interactions. Furthermore, appropriate regulation of Gsk3 activity is required to maintain the overall polarity of the radial glia scaffold. These findings reveal dynamism and interactions among radial glia that appear to be crucial contributors to the formation of the cerebral cortex. Related cell polarity determinants (Cdc42, Gsk3) differentially influence radial glial activities within the evolving radial glia scaffold to coordinate the formation of cerebral cortex

Arl13b in Primary Cilia Regulates the Migration and Placement of Interneurons in the Developing Cerebral Cortex

Coordinated migration and placement of interneurons and projection neurons lead to functional connectivity in the cerebral cortex; defective neuronal migration and the resultant connectivity changes underlie the cognitive defects in a spectrum of neurological disorders. Here we show that primary cilia play a guiding role in the migration and placement of postmitotic interneurons in the developing cerebral cortex, and that this process requires the ciliary protein, Arl13b. Through live imaging of interneuronal cilia we show migrating interneurons display highly dynamic primary cilia and we correlate cilia dynamics with the interneuron’s migratory state. We demonstrate that the guidance cue receptors essential for interneuronal migration localize to interneuronal primary cilia, but their concentration and dynamics are altered in the absence of Arl13b. Expression of Arl13b variants known to cause Joubert syndrome induce defective interneuronal migration, suggesting that defects in cilia-dependent interneuron migration may underlie the neurological defects in Joubert syndrome patients

Differential Regulation of Microtubule Severing by APC Underlies Distinct Patterns of Projection Neuron and Interneuron Migration

Coordinated migration of distinct classes of neurons to appropriate positions leads to the formation of functional neuronal circuitry in the cerebral cortex. Two major classes of cortical neurons, interneurons and projection neurons, utilize distinctly different modes (radial vs. tangential) and routes of migration to arrive at their final positions in the cerebral cortex. Here, we show that adenomatous polyposis coli (APC) modulates microtubule (MT) severing in interneurons to facilitate tangential mode of interneuron migration, but not the glial-guided, radial migration of projection neurons. APC regulates the stability and activity of the MT severing protein p60-katanin in interneurons to promote the rapid remodeling of neuronal processes necessary for interneuron migration. These findings reveal how severing and restructuring of MTs facilitate distinct modes of neuronal migration necessary for laminar organization of neurons in the developing cerebral cortex

Collusive oligopolistic politics : sedo and the political structure of early-nineteenth-century Chosŏn Korea

In contemporary Korean historiography, the reign periods of King Sunjo (r. 1800-1834), King Hŏnjong (r.1834-1849), and King Ch’ŏlchong (r. 1849-1863) are generally called “The Era of Sedo Politics” in Chosŏn Korea (1392-1910). In contemporary Korean historiography, the political theme of sedo predominated after the death of King Chŏngjo (r. 1776-1800), when national politics was exclusively led by a few powerful royal in-law families, most notably the Andong Kim and P’ungyang Cho clans, for sixty-three years. Obviously, those two major clans enjoyed extensive political authority and high social status in the nineteenth century. However, the negative images and common misconceptions in previous research on sedo politics have prevented scholars from understanding the period of sedo politics from a balanced angle and driven them to emphasize its unique features too much. This thesis rather paints the mainstream view of the political history of late Chosŏn Korea with a different brush. Starting off with a discussion of the definition and origin of the historical terminology sedo (世道 or 勢道), this paper questions more deeply the structure of sedo politics and re-examines previous research on characterizations of sedo politics. In addition, based on some statistical data and extensive research in genealogy records, this thesis will identify many points that cannot be illustrated or that are only partially explored in existing literature in the context of the 1800 to 1863 era of sedo politics. Through this re-examination, this research project will contribute to enlarging the vision of the political history of Korea in the first half of the nineteenth century, which has not been a major research topic among political historians of Korea, who have mainly dealt with struggles and conflicts for political power among various historical agents.Arts, Faculty ofAsian Studies, Department ofGraduat