Search

VAChT-Cre.Fast and VAChT-Cre.Slow mice selectively express Cre recombinase in approximately one half of postnatal somatic motor neurons. The mouse lines have been used in various studies with selective genetic modifications in adult motor neurons. In the present study, we crossed VAChT-Cre lines with a reporter line, CAG-Syp/tdTomato, in which synaptophysin-tdTomato fusion proteins are efficiently sorted to axon terminals, making it possible to label both cell bodies and axon terminals of motor neurons. In the mice, Syp/tdTomato fluorescence preferentially co-localized with osteopontin, a recently discovered motor neuron marker for slow-twitch fatigue-resistant (S) and fast-twitch fatigue-resistant (FR) types. The fluorescence did not preferentially co-localize with matrix metalloproteinase-9, a marker for fast-twitch fatigable (FF) motor neurons. In the neuromuscular junctions, Syp/tdTomato fluorescence was detected mainly in motor nerve terminals that innervate type I or IIa muscle fibers. These results suggest that the VAChT-Cre lines are Cre-drivers that have selectivity in S and FR motor neurons. In order to avoid confusion, we have changed the mouse line names from VAChT-Cre.Fast and VAChT-Cre.Slow to VAChT-Cre.Early and VAChT-Cre.Late, respectively. The mouse lines will be useful tools to study slow-type motor neurons, in relation to physiology and pathology.

Cell polarity depends on extrinsic spatial cues and intrinsic polarity proteins including PAR-aPKC proteins. In mammalian epithelial cells, cell-cell contacts provide spatial cues that activate the aPKC-PAR-3-PAR-6 complex to establish the landmark of the initial cellular asymmetry. PAR-1, a downstream target of the aPKC-PAR-3-PAR-6 complex, mediates further development of the apical and basolateral membrane domains. However, the relationships between the PAR-aPKC proteins and other extrinsic spatial cues provided by the extracellular matrix (ECM) remain unclear. Here, we show that PAR-1 colocalizes with laminin receptors and is required for the assembly of extracellular laminin on the basal surface of epithelial cells. Furthermore, PAR-1 regulates the basolateral localization of the dystroglycan (DG) complex, one of the laminin receptors essential for basement membrane formation. We also show that PAR-1 interacts with the DG complex and is required for the formation of a functional DG complex. These results reveal the presence of a novel inside-out pathway in which an intracellular polarity protein regulates the ECM organization required for epithelial cell polarity and tissue morphogenesis.

In Huntington's disease (HD), mutant Huntingtin, which contains expanded polyglutamine stretches, forms nuclear aggregates in neurons. The interactions of several transcriptional factors with mutant Huntingtin, as well as altered expression of many genes in HD models, imply the involvement of transcriptional dysregulation in the HD pathological process. The precise mechanism remains obscure, however. Here, we show that mutant Huntingtin aggregates interact with the components of the NF-Y transcriptional factor in vitro and in HD model mouse brain. An electrophoretic mobility shift assay using HD model mouse brain lysates showed reduction in NF-Y binding to the promoter region of HSP70, one of the NF-Y targets. RT–PCR analysis revealed reduced HSP70 expression in these brains. We further clarified the importance of NF-Y for HSP70 transcription in cultured neurons. These data indicate that mutant Huntingtin sequesters NF-Y, leading to the reduction of HSP70 gene expression in HD model mice brain. Because suppressive roles of HSP70 on the HD pathological process have been shown in several HD models, NF-Y could be an important target of mutant Huntingtin.

Background PAR-6, aPKC and PAR-3 are polarity proteins that co-operate in the establishment of cell polarity in Caenorhabditis elegans and Drosophila embryos. We have recently shown that mammalian aPKC is required for the formation of the epithelia-specific cell-cell junctional structure. We have also revealed that a mammalian PAR-6 forms a ternary complex with aPKC and ASIP/PAR-3, and localizes at the most apical end of the junctional complex in epithelial cells. Results The ternary complex formation and junctional co-localization of PAR-6 with aPKC and ASIP/PAR-3 are observed during the early stage of epithelial cell polarization. In addition, over-expression of the PAR-6 mutant with CRIB/PDZ domain in MDCK cells disturbs the cell-cell contact-induced junctional localization of tight junction proteins, as well as inhibiting TER development. Furthermore, the binding of Cdc42:GTP to the CRIB/PDZ domain of PAR-6 enhances the kinase activity of PAR-6-bound aPKC. Detailed analyses suggest that the binding of PAR-6 to aPKC has the intrinsic potential to activate aPKC, which is only released when Cdc42:GTP binds to the CRIB/PDZ domain. Conclusion The results indicate the involvement of PAR-6 in the aPKC function which is required for the cell-cell adhesion-induced formation of epithelial junctional structures, possibly through the cooperative regulation of aPKC activity with Cdc42.