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Michael Kiebler

Publications and source records attributed to Michael Kiebler.

5 recordsLinked to original sources
PubMed2006

A brain-specific microRNA regulates dendritic spine development.

MicroRNAs are small, non-coding RNAs that control the translation of target messenger RNAs, thereby regulating critical aspects of plant and animal development. In the mammalian nervous system, the spatiotemporal control of mRNA translation has an important role in synaptic development and plasticity. Although a number of microRNAs have been isolated from the mammalian brain, neither the specific microRNAs that regulate synapse function nor their target mRNAs have been identified. Here we show that a brain-specific microRNA, miR-134, is localized to the synapto-dendritic compartment of rat hippocampal neurons and negatively regulates the size of dendritic spines--postsynaptic sites of excitatory synaptic transmission. This effect is mediated by miR-134 inhibition of the translation of an mRNA encoding a protein kinase, Limk1, that controls spine development. Exposure of neurons to extracellular stimuli such as brain-derived neurotrophic factor relieves miR-134 inhibition of Limk1 translation and in this way may contribute to synaptic development, maturation and/or plasticity.

Animals↗
PubMed2005

Intracellular RNA sorting, transport and localization.

RNA localization and translational control are crucial for cellular fine-tuning of gene expression in space and time. A recent meeting in Tucson, Arizona pointed out mechanisms conserved across different species and cell types that contribute to the establishment of cell polarity and cell migration. Furthermore, it is becoming increasingly clear that these post-transcriptional control processes are relevant for various diseases.

Animals↗
PubMed2004

Chemically controlled formation of a DNA/calcium phosphate coprecipitate: application for transfection of mature hippocampal neurons.

Numerous methods exist for transfecting postmitotic neurons, for example, DNA/calcium phosphate coprecipitation, cationic lipids, viruses, and physical methods such as microinjection, electroporation, and biolistics. Most methods, however, are either toxic to the cell, yield only poor transfection efficiencies, or cells have to be electroporated before plating. In this article, we present a standardized and fast transfection method using DNA/calcium phosphate coprecipitates that efficiently transfer DNA into mature, postmitotic hippocampal neurons. Shifting to CO(2)-independent media with a well-defined pH allows for the tight control of the coprecipitate formation and for adjusting the transfection parameters for the individual DNA plasmid used. The two critical parameters for reproducible and efficient transfections are: the precise pH during crystal formation, and the incubation time of the cells with the coprecipitate. This improved procedure now enables biochemical approaches. By transfecting a dominant-positive Ras mutant, we activate the Erk/MAP kinase signal transduction pathway. Furthermore, using a siRNA plasmid directed against MAP2, the level of an endogenously expressed protein is down-regulated upon transfection. These two approaches demonstrate that the presented transient transfection method can now be used to address questions on a biochemical level in hippocampal neurons.

Animals↗
PubMed2003

Barentsz, a new component of the Staufen-containing ribonucleoprotein particles in mammalian cells, interacts with Staufen in an RNA-dependent manner.

Staufen1, the mammalian homolog of Drosophila Staufen, assembles into ribonucleoprotein particles (RNPs), which are thought to transport and localize RNA into dendrites of mature hippocampal neurons. We therefore investigated whether additional components of the RNA localization complex besides Staufen are conserved. One candidate is the mammalian homolog of Drosophila Barentsz (Btz), which is essential for the localization of oskar mRNA to the posterior pole of the Drosophila oocyte and is a component of the oskar RNA localization complex along with Staufen. In this study, we report the characterization of mammalian Btz, which behaves like a nucleocytoplasmic shuttling protein. When expressed in the Drosophila egg chamber, mammalian Btz is still able to interact with Drosophila Staufen and reach the posterior pole in the wild-type oocyte, but does not rescue the btz mutant phenotype. Most interestingly, we show by immunoprecipitation assays that Btz interacts with mammalian Staufen in an RNA-dependent manner through a conserved domain, which encompasses the region of homology to the Drosophila Btz protein and contains a novel conserved motif. One candidate for an RNA that mediates this interaction is the dendritically localized brain cytoplasmic 1 transcript. In addition, Btz and Staufen1 colocalize within particles in the cell body and, to a more variable extent, in dendrites of mature hippocampal neurons. Together, our data suggest that the mRNA transport machinery is conserved during evolution, and that mammalian Btz is an additional component of the dendritic RNPs in hippocampal neurons.

Amino Acid Motifs↗