Diego and Prickle regulate Frizzled planar cell polarity signalling by competing for Dishevelled binding

Epithelial planar cell polarity (PCP) is evident in the cellular organization of many tissues in vertebrates and invertebrates. In mammals, PCP signalling governs convergent extension during gastrulation and the organization of a wide variety of structures, including the orientation of body hair and sensory hair cells of the inner ear. In Drosophila melanogaster, PCP is manifest in adult tissues, including ommatidial arrangement in the compound eye and hair orientation in wing cells. PCP establishment requires the conserved Frizzled/Dishevelled PCP pathway. Mutations in PCP-pathway-associated genes cause aberrant orientation of body hair or inner-ear sensory cells in mice, or misorientation of ommatidia and wing hair in D. melanogaster. Here we provide mechanistic insight into Frizzled/Dishevelled signalling regulation. We show that the ankyrin-repeat protein Diego binds directly to Dishevelled and promotes Frizzled signalling. Dishevelled can also be bound by the Frizzled PCP antagonist Prickle. Strikingly, Diego and Prickle compete with one another for Dishevelled binding, thereby modulating Frizzled/Dishevelled activity and ensuring tight control over Frizzled PCP signalling.     

Marine actinobacteria: perspectives, challenges, future directions

In this paper we evaluate the current state of research on the biology biotechnology of marine actinobacteria. The topics covered include the abundance, diversity, novelty and biogeographic distribution of marine actinobacteria, ecosystem function, bioprospecting, and a new approach to the exploration of actinobacterial taxonomic space. An agenda for future marine actinobacterial research is suggested based upon consideration of the above issues.     

DNA double-strand breaks induce deletion of CTG.CAG repeats in an orientation-dependent manner in Escherichia coli

The influences of double-strand breaks (DSBs) within a triplet repeat sequence on its genetic instabilities (expansions and deletions) related to hereditary neurological diseases was investigated. Plasmids containing 43 or 70 CTG.CAG repeats or 43 CGG.CCG repeats were linearized in vitro near the center of the repeats and were transformed into parental, RecA-dependent homologous recombination-deficient, or RecBC exonuclease-deficient Escherichia coli. The resulting repair process considerably increased deletion of the repeating sequence compared to the circular DNA controls. Unexpectedly, the orientation of the insert relative to the unidirectional ColE1 origin of replication affected the amount of instability generated during the repair of the DSB. When the CTG strand was the template for lagging-strand synthesis, instability was increased, most markedly in the recA- strain. Results indicated that RecA and/or RecBC might play a role in DSB repair within the triplet repeat. Altering the length, orientation, and sequence composition of the triplet repeat suggested an important role of DNA secondary structures during repair intermediates. Hence, we hypothesize that ColE1 origin-dependent replication was involved during the repair of the DSB. A model is presented to explain the mechanisms of the observed genetic instabilities.     

Synergistic Cooperation between Two ClpB Isoforms in Aggregate Reactivation

Bacterial AAA⁺ ATPase ClpB cooperates with DnaK during reactivation of aggregated proteins. The ClpB-mediated disaggregation is linked to translocation of polypeptides through the channel in the oligomeric ClpB. Two isoforms of ClpB are produced in vivo: the full-length ClpB95 and ClpB80, which does not contain the substrate-interacting N-terminal domain. The biological role of the truncated isoform ClpB80 is unknown. We found that resolubilization of aggregated proteins in Escherichia coli after heat shock and reactivation of aggregated proteins in vitro and in vivo occurred at higher rates in the presence of ClpB95 with ClpB80 than with ClpB95 or ClpB80 alone. Combined amounts of ClpB95 and ClpB80 bound to aggregated substrates were similar to the amounts of either ClpB95 or ClpB80 bound to the substrates in the absence of another isoform. The ATP hydrolysis rate of ClpB95 with ClpB80, which is linked to the rate of substrate translocation, was not higher than the rates measured for the isolated ClpB95 or ClpB80. We postulate that a reaction step that takes place after substrate binding to ClpB and precedes substrate translocation is rate-limiting during aggregate reactivation, and its efficiency is enhanced in the presence of both ClpB isoforms. Moreover, we found that ClpB95 and ClpB80 form hetero-oligomers, which are similar in size to the homo-oligomers of ClpB95 or ClpB80. Thus, the mechanism of functional cooperation of the two isoforms of ClpB may be linked to their heteroassociation. Our results suggest that the functionality of other AAA⁺ ATPases may be also optimized by interaction and synergistic cooperation of their isoforms.     

Molecular characterization of the type I IFN receptor in two woodchuck species and detection of its expression in liver samples from woodchucks infected with woodchuck hepatitis virus (WHV)

Type I interferons (IFN-α/β) serve as the first line of defense against viral infection and share the same type I IFN receptor (IFNAR) complex, which is composed of IFNAR1 and -2. The Eastern woodchuck (Marmota monax) and Chinese woodchuck (Marmota himalayana) are suitable for studying hepatitis B virus (HBV) infection. Here, the complete or partial sequences of the IFNARs of both species were obtained and analyzed. Small interference RNAs targeting wIFNAR1 and -2 specifically down-regulated the expression of wIFNAR1 and -2 and the IFN-stimulated gene MxA in a woodchuck cell line, respectively. IFNAR2 was significantly up-regulated in primary woodchuck hepatocytes stimulated with IFN-α or -γ. The expression of woodchuck IFNAR1 and -2 was decreased in woodchucks chronically infected with woodchuck hepatitis virus (WHV). These results are essential for studying type I IFN-related innate immunity and therapy in hepadnaviral infection in the woodchuck model.     

PharmGKB: the Pharmacogenetics Knowledge Base

The Pharmacogenetics Knowledge Base (PharmGKB; http://www.pharmgkb.org/) contains genomic, phenotype and clinical information collected from ongoing pharmacogenetic studies. Tools to browse, query, download, submit, edit and process the information are available to registered research network members. A subset of the tools is publicly available. PharmGKB currently contains over 150 genes under study, 14 Coriell populations and a large ontology of pharmacogenetics concepts. The pharmacogenetic concepts and the experimental data are interconnected by a set of relations to form a knowledge base of information for pharmacogenetic researchers. The information in PharmGKB, and its associated tools for processing that information, are tailored for leading-edge pharmacogenetics research. The PharmGKB project was initiated in April 2000 and the first version of the knowledge base went online in February 2001.     

Temporal modulation transfer functions in the barn owl (<Emphasis Type="Italic">Tyto alba</Emphasis>)

Barn owls (Tyto alba) have evolved several specializations in their auditory system to achieve the high sensory acuity required for prey capture, including superior processing of interaural time differences and phase coding in the auditory periphery. Here, we tested whether barn owls are capable of high temporal resolution that may be a prerequisite for the accuracy in binaural processing. Temporal resolution was measured psychoacoustically and demonstrated in temporal modulation transfer functions. Four barn owls were trained in an operant task with food reward to detect sinusoidal amplitude modulations within an 800-ms gated white-noise burst or 800-ms periods of modulation in continuous white noise (spectrum levels of -5 dB and 15 dB SPL). Within the range of tested amplitude modulation frequencies from 5 Hz to 1280 Hz, barn owls' detection thresholds were lowest at 10-20 Hz. This sensitivity corresponds to an intensity-difference limen of between 0.9 dB and 1.4 dB. For all conditions, temporal modulation transfer functions showed band-pass characteristics with a high-frequency cutoff in the range of 37 Hz to 92 Hz, corresponding to minimum integration times of 4.3 ms and 1.7 ms, respectively. In summary, these data indicate a temporal resolution in the owl's auditory system that is good, but not unusual, compared to other vertebrates.     

Outline of A New Approach to Evaluate Ecological Integrity of Salt Marshes

The integrity of coastal salt marshes can be determined from the extent to which they provide key ecosystem services: food and habitat for fish and wildlife, good water quality, erosion and flood control, and recreation and cultural use. An outline of a new approach for linking ecosystem services with metrics of structure and function to evaluate the ecological integrity of salt marshes is described. One main objective of the approach is to determine whether differences in structure and function can be detected among salt marshes with similar geomorphology and hydrology but different degrees of anthropogenic stress. The approach is currently being applied to salt marshes of Narragansett Bay, RI, USA. Stable nitrogen isotopic ratios of the marsh biota reflected the nitrogen sources from the adjacent watersheds and were significantly correlated with percent residential land use. Results show that plant zonation significantly ( r = —0.82; p < 0.05) relates with percent residential land use and is potentially a sensitive indicator of anthropogenic disturbance of New England salt marshes. We are currently examining species diversity, denitrification rates, and susceptibility to erosion among the sites for additional indicators of salt marsh condition. Our results to date suggest that this approach will provide the methods needed for managers to systematically monitor and evaluate the integrity of salt marshes