Discovery of novel 2-(4-aryl-2-methylpiperazin-1-yl)-pyrimidin-4-ones as glycogen synthase kinase-3ß inhibitors.

We herein describe the results of further evolution of glycogen synthase kinase (GSK)-3ß inhibitors from our promising compounds containing a 3-methylmorpholine moiety. Transformation of the morpholine moiety into a piperazine moiety resulted in potent GSK-3ß inhibitors. SAR studies focused on the nitrogen atom of the piperazine moiety revealed that a phenyl group afforded potent inhibitory activity toward GSK-3ß. Docking studies indicated that the phenyl group on the piperazine nitrogen atom and the methyl group on the piperazine make cation-π and CH-π interactions with GSK-3ß respectively. 4-Methoxyphenyl analogue 29 showed most potent inhibitory activity toward GSK-3ß with good in vitro and in vivo pharmacokinetic profiles, and 29 demonstrated a significant decrease in tau phosphorylation after oral administration in mice.

p53 Deficiency rescues neuronal apoptosis but not differentiation in DNA polymerase beta-deficient mice.

In mammalian cells, DNA polymerase beta (Polbeta) functions in base excision repair. We have previously shown that Polbeta-deficient mice exhibit extensive neuronal cell death (apoptosis) in the developing nervous system and that the mice die immediately after birth. Here, we studied potential roles in the phenotype for p53, which has been implicated in DNA damage sensing, cell cycle arrest, and apoptosis. We generated Polbeta(-/-) p53(-/-) double-mutant mice and found that p53 deficiency dramatically rescued neuronal apoptosis associated with Polbeta deficiency, indicating that p53 mediates the apoptotic process in the nervous system. Importantly, proliferation and early differentiation of neuronal progenitors in Polbeta(-/-) p53(-/-) mice appeared normal, but their brains obviously displayed cytoarchitectural abnormalities; moreover, the mice, like Polbeta(-/-) p53(+/+) mice, failed to survive after birth. Thus, we strongly suggest a crucial role for Polbeta in the differentiation of specific neuronal cell types.

Generation of reelin-positive marginal zone cells from the caudomedial wall of telencephalic vesicles.

An early and fundamental step of the laminar organization of developing neocortex is controlled by the developmental programs that critically depend on the activities of reelin-positive cells in the marginal zone. However, the ontogeny of reelin-positive cells remained elusive. To gain insights into the spatial and temporal regulation of reelin-positive marginal zone cell development, we used a transgenic mouse line in which we defined the green fluorescent protein (GFP) transgene as a novel reliable molecular marker of reelin-positive marginal zone cells from the early stages of their development. We further used exo utero electroporation-mediated gene transfer that allows us to mark progenitor cells and monitor the descendants in the telencephalon in vivo. We show here the generation of reelin-positive marginal zone cells from the caudomedial wall of telencephalic vesicles, including the cortical hem, where the prominent expression of GFP is initially detected. These neurons tangentially migrate at the cortical marginal zone and are distributed throughout the entire neocortex in a caudomedial-high to rostrolateral-low gradient during the dynamic developmental period of corticogenesis. Therefore, our findings on reelin-positive marginal zone cells, in addition to the cortical interneurons, add to the emerging view that the neocortex consists of neuronal subtypes that originate from a focal source extrinsic to the neocortex, migrate tangentially into the neocortex, and thereby underlie neural organization of the neocortex.

The Timing of Appearance and Pathway of Migration of Cranial Neural Crest-derived Precursors of Melanocytes in Chick Embryos: (neural crest cells/melanocyte/migration/chick embryo).

The timing of appearance and pathway of migration of precursors of melanocytes in cranial regions of chick embryos were examined by the monoclonal antibody MEBL-1, which can identify precursors of melanocytes soon after their emigration from the neural tube (7). Precursors of melanocytes were first detected on the dorsal side of the mesencephalic neural tube at stage 16, when other neural crest cells had already left the dorsal side of the neural tube. Then precursors of melanocytes at more rostral and caudal levels appeared. After the first appearance on the neural tube, precursors of melanocytes migrated along a dorsolateral pathway under the superficial ectoderm, which followed other neural crest cells. These results indicate that precursors of melanocytes migrate along spatially the same pathway as other neural crest cells, but temporally the different time as considered previously.

Localized distribution of a novel mesenchyme-specific antigen in developing chick digestive organs : Comparison with the distribution of fibronectin, laminin and tenascin.

The mesenchymes of the two avian stomachs, the proventriculus (glandular stomach) and the gizzard (muscular stomach), exert different inductive influences on stomach epithelial morphogenesis and cytodifferentiation. To search for a molecular difference between these two mesenchymes, we have produced monoclonal antibodies directed against chick proventriculi and gizzards and have screened those that differently recognized proventricular and gizzard mesenchymes. Finally, we obtained one monoclonal antibody, T95, and characterized it immunohistochemically. T95 characteristically stains the mesenchymal region just under the gizzard epithelium from 6 days of incubation onward to about 10 days of incubation, while it stains proventricular mesenchyme only weakly during these stages. We also examined immunohistochemically the distribution of well-known extracellular matrix molecules, such as fibronectin, laminin and tenascin, and none of them showed the same localization as T95 antigen in proventricular and gizzard mesenchymes. These results indicate that T95 will be an interesting marker which distinguishes the proventricular and gizzard mesenchymes, at the time when they have different inductive ability.

Transfilter analysis of the inductive influence of proventricular mesenchyme on stomach epithelial differentiation of chick embryos.

To clarify the precise conditions under which chick embryonic proventricular mesenchyme can induce proventricular epithelial differentiation, transfilter experiments were carried out. Six-day proventricular epithelium formed glands and expressed pepsinogen when a Nucleopore filter with a pore size of more than 0.6 µm, but not 0.2 µm, was inserted between the epithelium and the proventricular mesenchyme. The larger the pore size of the filter, the more elongated the glands and the more pepsinogen was induced in the explants. The quail nuclear marker and scanning electron microscopy were used to examine penetration of mesenchymal cells through the Nuclepore filter. The filter of more than 0.2 µm pore size allowed cell processes of mesenchymal cells to pass through. However, only the filter with a pore size of more than 0.6 µm allowed actual migration of mesenchymal cells through the filter, and the larger the pore size of the filter, the more mesenchymal cells passed through. Under the same conditions 6-day and 4.5-day gizzard epithelium formed glands and expressed pepsinogen. These results indicate that a flow of diffusible substances through a Nuclepore filter and even direct contact of a few short cell processes of mesenchymal cells with epithelial cells are not sufficient for induction, and that direct contact of mesenchymal cell processes and/or mesenchymal cells with epithelial cells over a considerably wide area may be prerequisite for the induction.