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4108 Publications

Showing 3461-3470 of 4108 results
Riddiford Lab
01/01/08 | Krüppel homolog 1 (Kr-h1) mediates juvenile hormone action during metamorphosis of Drosophila melanogaster.
Minakuchi C, Zhou X, Riddiford LM
Mechanisms of Development. 2008 Jan-Feb;125:91-105. doi: 10.1016/j.mod.2007.10.002

Juvenile hormone (JH) given at pupariation inhibits bristle formation and causes pupal cuticle formation in the abdomen of Drosophila melanogaster due to its prolongation of expression of the transcription factor Broad (BR). In a microarray analysis of JH-induced gene expression in abdominal integument, we found that Krüppel homolog 1 (Kr-h1) was up-regulated during most of adult development. Quantitative real-time PCR analyses showed that Kr-h1 up-regulation began at 10h after puparium formation (APF), and Kr-h1 up-regulation occurred in imaginal epidermal cells, persisting larval muscles, and larval oenocytes. Ectopic expression of Kr-h1 in abdominal epidermis using T155-Gal4 to drive UAS-Kr-h1 resulted in missing or short bristles in the dorsal midline. This phenotype was similar to that seen after a low dose of JH or after misexpression of br between 21 and 30 h APF. Ectopic expression of Kr-h1 prolonged the expression of BR protein in the pleura and the dorsal tergite. No Kr-h1 was seen after misexpression of br. Thus, Kr-h1 mediates some of the JH signaling in the adult abdominal epidermis and is upstream of br in this pathway. We also show for the first time that the JH-mediated maintenance of br expression in this epidermis is patterned and that JH delays the fusion of the imaginal cells and the disappearance of Dpp in the dorsal midline.

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01/01/08 | Local potential connectivity in cat primary visual cortex.
Stepanyants A, Hirsch JA, Martinez LM, Kisvárday ZF, Ferecskó AS, Chklovskii DB
Cerebral Cortex. 2008 Jan;18(1):13-28. doi: 10.1093/cercor/bhm027

Time invariant description of synaptic connectivity in cortical circuits may be precluded by the ongoing growth and retraction of dendritic spines accompanied by the formation and elimination of synapses. On the other hand, the spatial arrangement of axonal and dendritic branches appears stable. This suggests that an invariant description of connectivity can be cast in terms of potential synapses, which are locations in the neuropil where an axon branch of one neuron is proximal to a dendritic branch of another neuron. In this paper, we attempt to reconstruct the potential connectivity in local cortical circuits of the cat primary visual cortex (V1). Based on multiple single-neuron reconstructions of axonal and dendritic arbors in 3 dimensions, we evaluate the expected number of potential synapses and the probability of potential connectivity among excitatory (pyramidal and spiny stellate) neurons and inhibitory basket cells. The results provide a quantitative description of structural organization of local cortical circuits. For excitatory neurons from different cortical layers, we compute local domains, which contain their potentially pre- and postsynaptic excitatory partners. These domains have columnar shapes with laminar specific radii and are roughly of the size of the ocular dominance column. Therefore, connections between most excitatory neurons in the ocular dominance column can be implemented by local synaptogenesis. Structural connectivity involving inhibitory basket cells is generally weaker than excitatory connectivity. Here, only nearby neurons are capable of establishing more than one potential synapse, implying that within the ocular dominance column these connections have more limited potential for circuit remodeling.

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01/01/08 | Natural image denoising with convolutional networks.
Jain V, Seung HS
Neural Information Processing Systems. 2008 :
01/01/08 | Rate-efficient visual correspondences using random projections.
Yeo C, Ahammad P, Ramchandran K
IEEE International Conference on Image Processing. 2008:

We consider the problem of establishing visual correspondences in a distributed and rate-efficient fashion by broadcasting compact descriptors. Establishing visual correspondences is a critical task before other vision tasks can be performed in a camera network. We use coarsely quantized random projections of descriptors to build binary hashes, and use the hamming distance between binary hashes as a matching criterion. In this work, we show that the hamming distance between the binary hashes has a binomial distribution, with parameters that are a function of the number of random projections and the euclidean distance between the original descriptors. We present experimental results that verify our result, and show that for the task of finding visual correspondences, sending binary hashes is more rate-efficient than prior approaches.

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01/01/08 | The Pfam protein families database.
Finn RD, Tate J, Mistry J, Coggill PC, Sammut SJ, Hotz H, Ceric G, Forslund K, Eddy SR, Sonnhammer EL, Bateman A
Nucleic Acids Research. 2008 Jan;36(Database Issue):D281-8. doi: 10.1093/nar/gkm960

Pfam is a comprehensive collection of protein domains and families, represented as multiple sequence alignments and as profile hidden Markov models. The current release of Pfam (22.0) contains 9318 protein families. Pfam is now based not only on the UniProtKB sequence database, but also on NCBI GenPept and on sequences from selected metagenomics projects. Pfam is available on the web from the consortium members using a new, consistent and improved website design in the UK (http://pfam.sanger.ac.uk/), the USA (http://pfam.janelia.org/) and Sweden (http://pfam.sbc.su.se/), as well as from mirror sites in France (http://pfam.jouy.inra.fr/) and South Korea (http://pfam.ccbb.re.kr/).

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01/01/08 | Vector and parameters for targeted transgenic RNA interference in Drosophila melanogaster.
Ni J, Markstein M, Binari R, Pfeiffer B, Liu L, Villalta C, Booker M, Perkins L, Perrimon N
Nature Methods. 2008 Jan;5(1):49-51. doi: 10.1038/nmeth1146

The conditional expression of hairpin constructs in Drosophila melanogaster has emerged in recent years as a method of choice in functional genomic studies. To date, upstream activating site-driven RNA interference constructs have been inserted into the genome randomly using P-element-mediated transformation, which can result in false negatives due to variable expression. To avoid this problem, we have developed a transgenic RNA interference vector based on the phiC31 site-specific integration method.

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12/31/07 | Huntingtin-interacting protein 14, a palmitoyl transferase required for exocytosis and targeting of CSP to synaptic vesicles.
Ohyama T, Verstreken P, Ly CV, Rosenmund T, Rajan A, Tien A, Haueter C, Schulze KL, Bellen HJ
The Journal of Cell Biology. 2007 Dec 31;179(7):1481-96. doi: 10.1083/jcb.200710061

Posttranslational modification through palmitoylation regulates protein localization and function. In this study, we identify a role for the Drosophila melanogaster palmitoyl transferase Huntingtin-interacting protein 14 (HIP14) in neurotransmitter release. hip14 mutants show exocytic defects at low frequency stimulation and a nearly complete loss of synaptic transmission at higher temperature. Interestingly, two exocytic components known to be palmitoylated, cysteine string protein (CSP) and SNAP25, are severely mislocalized at hip14 mutant synapses. Complementary DNA rescue and localization experiments indicate that HIP14 is required solely in the nervous system and is essential for presynaptic function. Biochemical studies indicate that HIP14 palmitoylates CSP and that CSP is not palmitoylated in hip14 mutants. Furthermore, the hip14 exocytic defects can be suppressed by targeting CSP to synaptic vesicles using a chimeric protein approach. Our data indicate that HIP14 controls neurotransmitter release by regulating the trafficking of CSP to synapses.

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12/28/07 | Function of the Drosophila CPEB protein Orb2 in long-term courtship memory.
Keleman K, Krüttner S, Alenius M, Dickson BJ
Nature Neuroscience. 2007 Dec 28;10(12):1587-93. doi: 10.1038/nn1996

Both long-term behavioral memory and synaptic plasticity require protein synthesis, some of which may occur locally at specific synapses. Cytoplasmic polyadenylation element-binding (CPEB) proteins are thought to contribute to the local protein synthesis that underlies long-term changes in synaptic efficacy, but a role has not been established for them in the formation of long-term behavioral memory. We found that the Drosophila melanogaster CPEB protein Orb2 is acutely required for long-term conditioning of male courtship behavior. Deletion of the N-terminal glutamine-rich region of Orb2 resulted in flies that were impaired in their ability to form long-term, but not short-term, memory. Memory was restored by expressing Orb2 selectively in fruitless (fru)-positive gamma neurons of the mushroom bodies and by providing Orb2 function in mushroom bodies only during and shortly after training. Our data thus demonstrate that a CPEB protein is important in long-term memory and map the molecular, spatial and temporal requirements for its function in memory formation.

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12/20/07 | HCN1 channels constrain synaptically evoked Ca2+ spikes in distal dendrites of CA1 pyramidal neurons.
Tsay D, Dudman JT, Siegelbaum SA
Neuron. 2007 Dec 20;56(6):1076-89. doi: 10.1016/j.neuron.2007.11.015

HCN1 hyperpolarization-activated cation channels act as an inhibitory constraint of both spatial learning and synaptic integration and long-term plasticity in the distal dendrites of hippocampal CA1 pyramidal neurons. However, as HCN1 channels provide an excitatory current, the mechanism of their inhibitory action remains unclear. Here we report that HCN1 channels also constrain CA1 distal dendritic Ca2+ spikes, which have been implicated in the induction of LTP at distal excitatory synapses. Our experimental and computational results indicate that HCN1 channels provide both an active shunt conductance that decreases the temporal integration of distal EPSPs and a tonic depolarizing current that increases resting inactivation of T-type and N-type voltage-gated Ca2+ channels, which contribute to the Ca2+ spikes. This dual mechanism may provide a general means by which HCN channels regulate dendritic excitability.

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Svoboda Lab
12/20/07 | Locally dynamic synaptic learning rules in pyramidal neuron dendrites.
Harvey CD, Svoboda K
Nature. 2007 Dec 20;450(7173):1195-200. doi: 10.1038/nature06416

Long-term potentiation (LTP) of synaptic transmission underlies aspects of learning and memory. LTP is input-specific at the level of individual synapses, but neural network models predict interactions between plasticity at nearby synapses. Here we show in mouse hippocampal pyramidal cells that LTP at individual synapses reduces the threshold for potentiation at neighbouring synapses. After input-specific LTP induction by two-photon glutamate uncaging or by synaptic stimulation, subthreshold stimuli, which by themselves were too weak to trigger LTP, caused robust LTP and spine enlargement at neighbouring spines. Furthermore, LTP induction broadened the presynaptic-postsynaptic spike interval for spike-timing-dependent LTP within a dendritic neighbourhood. The reduction in the threshold for LTP induction lasted approximately 10 min and spread over approximately 10 microm of dendrite. These local interactions between neighbouring synapses support clustered plasticity models of memory storage and could allow for the binding of behaviourally linked information on the same dendritic branch.

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