Dapper Antagonist of Catenin-1 Cooperates with Dishevelled-1 during Postsynaptic Development in Mouse Forebrain GABAergic Interneurons

Synaptogenesis has been extensively studied along with dendritic spine development in glutamatergic pyramidal neurons, however synapse development in cortical interneurons, which are largely aspiny, is comparatively less well understood. Dact1, one of 3 paralogous Dact (Dapper/Frodo) family members in mammals, is a scaffold protein implicated in both the Wnt/β-catenin and the Wnt/Planar Cell Polarity pathways. We show here that Dact1 is expressed in immature cortical interneurons. Although Dact1 is first expressed in interneuron precursors during proliferative and migratory stages, constitutive Dact1 mutant mice have no major defects in numbers or migration of these neurons. However, cultured cortical interneurons derived from these mice have reduced numbers of excitatory synapses on their dendrites. We selectively eliminated Dact1 from mouse cortical interneurons using a conditional knock-out strategy with a Dlx-I12b enhancer-Cre allele, and thereby demonstrate a cell-autonomous role for Dact1 during postsynaptic development. Confirming this cell-autonomous role, we show that synapse numbers in Dact1 deficient cortical interneurons are rescued by virally-mediated re-expression of Dact1 specifically targeted to these cells. Synapse numbers in these neurons are also rescued by similarly targeted expression of the Dact1 binding partner Dishevelled-1, and partially rescued by expression of Disrupted in Schizophrenia-1, a synaptic protein genetically implicated in susceptibility to several major mental illnesses. In sum, our results support a novel cell-autonomous postsynaptic role for Dact1, in cooperation with Dishevelled-1 and possibly Disrupted in Schizophrenia-1, in the formation of synapses on cortical interneuron dendrites.     

Synthesis of 18O-labeled RNA for application to kinetic studies and imaging

Radioisotopes and fluorescent compounds are frequently used for RNA labeling but are unsuitable for clinical studies of RNA drugs because of the risk from radiation exposure or the nonequivalence arising from covalently attached fluorophores. Here, we report a practical phosphoramidite solid-phase synthesis of ¹⁸O-labeled RNA that avoids these disadvantages, and we demonstrate its application to quantification and imaging. The synthesis involves the introduction of a nonbridging ¹⁸O atom into the phosphate group during the oxidation step of the synthetic cycle by using ¹⁸O water as the oxygen donor. The ¹⁸O label in the RNA was stable at pH 3–8.5, while the physicochemical and biological properties of labeled and unlabeled short interfering RNA were indistinguishable by circular dichroism, melting temperature and RNA-interference activity. The ¹⁸O/¹⁶O ratio as measured by isotope ratio mass spectrometry increased linearly with the concentration of ¹⁸O-labeled RNA, and this technique was used to determine the blood concentration of ¹⁸O-labeled RNA after administration to mice. ¹⁸O-labeled RNA transfected into human A549 cells was visualized by isotope microscopy. The RNA was observed in foci in the cytoplasm around the nucleus, presumably corresponding to endosomes. These methodologies may be useful for kinetic and cellular-localization studies of RNA in basic and pharmaceutical studies.     

Tests of the accuracy of cladograms in Gilia (Polemoniaceae) and some other angiosperm genera

 This paper deals with the use of cladistic methods and cladograms in phylogeny reconstruction in plant groups containing numerous taxa. How accurate are the cladograms as to details? Accuracy tests at the level of details require an independently known phylogeny, which excludes most plant groups, but such tests can be carried out in domesticated and experimental plant groups which have documented pedigrees. Four such tests are known and are presented here: a new case in Gilia and three previously published cases in Avena, Hordeum, and Helianthus. The four cases include domesticated and experimental plants, use of morphological and molecular evidence, and presence of dichotomous as well as reticulate phylogenies. The cladograms of the four plant groups all differ in significant details from the known pedigrees. These results are discussed in relation to problems of interpretation of cladograms. Received March 21, 2000 Accepted August 16, 2001     

The first vitamin B6 zinc complex, pyridoxinato-zinc acetate: A 1D coordination polymer with polar packing through strong inter-chain hydrogen bonding

The biologically important pyridoxinato(1−) ligand (anionic vitamin B₆) shows the rare phenolate-hydroxymethyl chelation plus bridging mode through the pyridine-nitrogen atom towards zinc(II) to give the one-dimensional (1D) coordination polymer {(acetato-κO)-aqua-μ-[2-methyl-3-oxy-4,5-di(hydroxymethyl)pyridine-κN:O,O′]zinc(II)}·monohydrate with polar packing of adjacent chains along the polar c axis (in space group Pc) through strong inter-chain hydrogen bonding.     

The detection of fish pathogenVibrio anguillarum in water and fish using a species-specific DNA probe combined with membrane filtration

The marine bacteriumVibrio anguillarum causes disease in fish worldwide and is particularly devastating in aquaculture. Little is known about the ecology ofV. anguillarum in the environment and how this may relate to the pathogenicity of this organism. Combining membrane filtration and a species-specific DNA probe, culturableV. anguillarum cells were detected in water from three habitats and in chinook salmon (Onchorynchus tshawytscha) tissue samples. Results show that different marine habitats have a marked effect on cell numbers and that water temperature may play a role in the culturability and distribution ofV. anguillarum. Vibrio anguillarum was detected from the gills of salmon within 24 h of transfer of fingerlings from freshwater to seawater, with cell numbers reaching a concentration of 1.9 × 10² cells g^–1 tissue 28 days post transfer.Vibrio anguillarum cell numbers were low in the colon throughout the study, andV. anguillarum was not detected in healthy kidney samples. The methodology reported in this paper allows the accurate quantification of culturableV. anguillarum cells and has allowed a preliminary study of the ecology of this species.