Hot off the presses! Jun 23 Curr Biol

The Jun 23 issue of the Curr Biol is now up on Pubget (About Curr Biol): if you're at a subscribing institution, just click the link in the latest link at the home page. (Note you'll only be able to get all the PDFs in the issue if your institution subscribes to Pubget.)

Latest Articles Include:

• Beefed up
  - Curr Biol 19(12):R463-R464 (2009)
  One of the key threats to the Amazon rainforest comes from a burgeoning beef business according to a new report, writes Nigel Williams.
• Fence protection progress
  - Curr Biol 19(12):R465 (2009)
  A 20-year project of fencing in the Aberdare National Park in Kenya is nearing completion. Michael Gross reports.
• Kept out
  - Curr Biol 19(12):R466 (2009)
  Fencing may be blocking some mass migrations. Nigel Williams reports.
• Cheek by jowl
  - Curr Biol 19(12):R466-R467 (2009)
  Biodiversity and other benefits can be met even in highly managed human landscapes. Nigel Williams reports.
• Island refuge
  - Curr Biol 19(12):R468-R469 (2009)
  An artificial island in eastern Turkey created by a team of biologists is proving a haven for wildlife. Nigel Williams reports.
• Ancient insights
  - Curr Biol 19(12):R469 (2009)
  
• Jon Driver
  - Curr Biol 19(12):R470-R471 (2009)
  
• The BBSome
  - Curr Biol 19(12):R472-R473 (2009)
  
• Animal asymmetry
  - Curr Biol 19(12):R473-R477 (2009)
  
• Tool-use induces morphological updating of the body schema
  - Curr Biol 19(12):R478-R479 (2009)
  To control bodily movements the human brain relies on a somatosensory representation referred to as the body schema [1]. The almost century-old hypothesis that tool-use induces plastic changes resulting in the tool being incorporated in the body schema is nowadays widely accepted. Whether this somatosensory representation is truly modified remains unknown, however, as tool-use has never been shown to affect arm motor behaviour. Here we report that using a mechanical grabber that physically extends the arm does alter the kinematics of subsequent free-hand grasping movements. Remarkably, tool-use after-effects generalise to pointing movements, despite the absence of specific tool-training. Furthermore, this effect is driven by an increase of the represented length of the arm: after tool-use, subjects localised touches delivered on the elbow and middle fingertip of their arm as if they were farther apart. These findings indicate that tool-use alters the body schema, and al so show that what is modified is the somatosensory representation of intrinsic properties of the body morphology.
• Sleep: What Goes Up Must Come Down
  - Curr Biol 19(12):R480-R482 (2009)
  The function of sleep is hotly contested. Two recent studies suggest that fly sleep may be required to rescale synapses in the brain.
• Chromosome Segregation: Monopolin Goes Spindle
  - Curr Biol 19(12):R482-R484 (2009)
  At anaphase onset the mitotic spindle undergoes dramatic changes in order to segregate sister chromatids. Surprisingly, the monopolin complex, best known for its role at kinetochores in meiosis, is now shown to localize to, and stabilize, the mitotic anaphase spindle.
• Learning and Memory: While You Rest, Your Brain Keeps Working
  - Curr Biol 19(12):R484-R486 (2009)
  A recent study shows that brain activity recorded while the human subject is at 'rest' is significantly affected by a prior learning episode. These results suggest that understanding resting brain activity may be critical to understanding how humans learn from experience.
• Cognitive Ecology: Environmental Dependence of the Fitness Costs of Learning
  - Curr Biol 19(12):R486-R488 (2009)
  A recent study has found that butterflies maintain behavioural plasticity useful to them in rare environments by reducing associated costs in common environments. Butterflies use innate sensory biases to locate common green hosts, but learn to modify these preferences to find rare, red host-plants.
• Oogenesis: Making the Mos of Meiosis
  - Curr Biol 19(12):R489-R491 (2009)
  Meiosis is an ancient type of cell division whose advent allowed the evolution of sexual reproduction. The evolutionary history of the specialization that allowed gamete production to emerge from a simple reduction division has been unclear. New data now suggest that the molecular mechanisms involved in animal oocyte specialization may have origins that predate the emergence of bilaterian animals.
• Olfaction: Chemical Signposts along the Silk Road
  - Curr Biol 19(12):R491-R493 (2009)
  A recent study on the reception of olfactory cues by silkworm larvae illustrates how the convergence of genomic, physiological and ecological data promises to shed light on the origins and evolution of chemically mediated interactions between plants and insects.
• Visual Perception: Saccadic Omission — Suppression or Temporal Masking?
  - Curr Biol 19(12):R493-R496 (2009)
  Although we don't perceive visual stimuli during saccadic eye movements, new evidence shows that our brains do process these stimuli and they can influence our subsequent visual perception.
• Antigenic Variation: Extending the Reach of Telomeric Silencing
  - Curr Biol 19(12):R496-R498 (2009)
  Immune evasion in the parasitic African trypanosome relies upon the silencing of variant surface glycoprotein genes that are found adjacent to telomeres. Work on the RAP1 telomere-binding protein now indicates that silencing spreads over a sufficient distance to repress these genes.
• Cellular and Network Mechanisms of Operant Learning-Induced Compulsive Behavior in Aplysia
  - Curr Biol 19(12):975-984 (2009)
  Background Learning in exploratory and goal-directed behaviors can modify decision-making processes in the initiation of appropriate action and thereby transform the irregular and infrequent expression of such behaviors into inflexible, compulsive-like repetitive actions. However, the neuronal mechanisms underlying such learning-derived behavioral plasticity remain poorly understood. Results Appetitive operant conditioning, a form of associative learning, produces a long-lasting switch in the mollusk Aplysia's food-seeking behavior from irregular, impulsive-like radula biting movements into stereotyped, compulsive-like recurrences of this cyclic act. Using isolated buccal ganglia, we recorded intracellularly from an electrically coupled subset of feeding-network neurons whose spontaneous burst discharge is responsible for instigating the motor pattern underlying each radula bite cycle. We report that the sporadic production of biting patterns in preparations from naive and noncontingently trained animals derives from the inherently variable and incoherent bursting of these pattern-initiating neurons that are each randomly capable of triggering a given bite. However, the accelerated rhythmically recurring expression of radula motor patterns after contingent-reward training in vivo arises from a regularization and synchronization of burst discharge in the pattern-i nitiating cells through a promotion of stereotyped burst-generating oscillations and an increase in the strength of their electrical coupling. Conclusions Our results show that plasticity in the spatiotemporal organization of pacemaker bursting, both within and between components of an action-initiating neuronal subcircuit, provides novel cellular substrates by which operant learning alters the recurrent expression of a simple goal-directed behavior.
• Phosphorylation State Defines Discrete Roles for Monopolin in Chromosome Attachment and Spindle Elongation
  - Curr Biol 19(12):985-995 (2009)
  Background It is unknown how oscillations in Cdk1 activity drive the dramatic changes in chromosome and spindle dynamics that occur at the metaphase/anaphase transition. Results We show that the Schizosaccharomyces pombe monopolin complex has distinct functions in metaphase and anaphase that are determined by the phosphorylation state of its Mde4 subunit. When Cdk1 activity is high in metaphase, Mde4 is hyperphosphorylated on Cdk1 phosphorylation sites and localizes to kinetochores. A nonphosphorylatable mutant of Mde4 does not localize to kinetochores, appears prematurely on the metaphase spindle, and interferes with spindle dynamics and chromosome segregation, illustrating the importance of Cdk1 phosphorylation in regulating metaphase monopolin activity. When Cdk1 activity drops in anaphase, dephosphorylation of Mde4 triggers monopolin localization to the mitotic spindle, where it promotes spindle elongation and integrity, coupling the late mitotic loss of Cdk1 activity to anaphase spindle dynamics. Conclusions Together, these findings illustrate how the sequential phosphorylation and dephosphorylation of monopolin helps ensure the orderly execution of discrete steps in mitosis.
• Lateralized Gustatory Behavior of C. elegans Is Controlled by Specific Receptor-Type Guanylyl Cyclases
  - Curr Biol 19(12):996-1004 (2009)
  Background Even though functional lateralization is a common feature of many nervous systems, it is poorly understood how lateralized neural function is linked to lateralized gene activity. A bilaterally symmetric pair of C. elegans gustatory neurons, ASEL and ASER, senses a number of chemicals in a left/right asymmetric manner and therefore serves as a model to study the genetic basis of functional lateralization. The extent of functional lateralization of the ASE neurons and genes responsible for the left/right asymmetric activity of ASEL and ASER is unknown. Results We show here that a substantial number of salt ions are sensed in a left/right asymmetric manner and that lateralized salt responses allow the worm to discriminate between distinct salt cues. To identify molecules that may be involved in sensing salt ions and/or transmitting such sensory information, we examined the chemotaxis behavior of animals harboring mutations in eight different receptor-type, transmembrane guanylyl cyclases (encoded by gcy genes), which are expressed in either ASEL (gcy-6, gcy-7, gcy-14), ASER (gcy-1, gcy-4, gcy-5, gcy-22), or ASEL and ASER (gcy-19). Disruption of a particular ASER-expressed gcy gene, gcy-22, results in a broad chemotaxis defect to nearly all salts sensed by ASER, as well as to a left/right asymmetrically sensed amino acid. In contrast, disruption of other gcy genes resulted in highly salt ion-specific chemosensory defects. Conclusions Our findings broaden our understanding of lateralities in neural function, provide insights into how this laterality is molecularly encoded, and reveal an unusual multitude of molecules involved in gustatory signal transduction.
• Control of Centriole Length by CPAP and CP110
  - Curr Biol 19(12):1005-1011 (2009)
  Centrioles function as the major components of centrosomes, which organize microtubule (MT) arrays in proliferating cells, and as basal bodies for primary cilia formation in quiescent cells. Centrioles and basal bodies are structurally similar, barrel-shaped organelles composed of MTs. In proliferating cells, two new centrioles, termed procentrioles, form during the S phase of the cell cycle in close proximity to the proximal ends of the two preexisting parental centrioles, often at a near-orthogonal angle [1]. Considerable progress has been made toward understanding the biogenesis of centrioles, but the mechanisms that determine their lengths remain unknown. Here we show that overexpression of the centriolar protein CPAP in human cells enhances the accumulation of centriolar tubulin, leading to centrioles of strikingly increased length. Consistent with earlier work [2], we also find that elongated MT structures can be induced by depletion of the distal end-capping prot ein CP110 from centrioles. Importantly, though, these structures differ from genuine primary cilia. We thus propose that CPAP and CP110 play antagonistic roles in determining the extent of tubulin addition during centriole elongation, thereby controlling the length of newly formed centrioles.
• Overly Long Centrioles and Defective Cell Division upon Excess of the SAS-4-Related Protein CPAP
  - Curr Biol 19(12):1012-1018 (2009)
  The centrosome is the principal microtubule organizing center (MTOC) of animal cells [1]. Accurate centrosome duplication is fundamental for genome integrity and entails the formation of one procentriole next to each existing centriole, once per cell cycle. The procentriole then elongates to eventually reach the same size as the centriole. The mechanisms that govern elongation of the centriolar cylinder and their potential relevance for cell division are not known. Here, we show that the SAS-4-related protein CPAP [2] is required for centrosome duplication in cycling human cells. Furthermore, we demonstrate that CPAP overexpression results in the formation of abnormally long centrioles. This also promotes formation of more than one procentriole in the vicinity of such overly long centrioles, eventually resulting in the presence of supernumerary MTOCs. This in turn leads to multipolar spindle assembly and cytokinesis defects. Overall, our findings suggest that centriole length must be carefully regulated to restrict procentriole number and thus ensure accurate cell division.
• Transequatorial Migrations by Basking Sharks in the Western Atlantic Ocean
  - Curr Biol 19(12):1019-1022 (2009)
  The world's second largest fish, the basking shark (Cetorhinus maximus), is broadly distributed in boreal to warm temperate latitudes of the Atlantic and Pacific oceans from shallow coastal waters to the open ocean [1] and [2]. Previous satellite archival tagging in the North Atlantic has shown that basking sharks move seasonally, are often associated with productive frontal zones [3] and [4], and may make occasional dives to mesopelagic depths [3] and [5]. However, basking sharks are thought to be restricted to temperate latitudes, and the extent to which they exploit deeper-water habitat remains enigmatic. Via satellite archival tags and a novel geolocation technique, we demonstrate here that basking sharks are seasonal migrants to mesopelagic tropical waters. Tagged sharks moved from temperate feeding areas off the coast of southern New England to the Bahamas, the Caribbean Sea, and onward to the coast of South America and into the Southern Hemisphere. When in these areas, basking sharks descended to mesopelagic depths and in some cases remained there for weeks to months at a time. Our results demonstrate that tropical waters are not a barrier to migratory connectivity for basking shark populations and highlight the need for global conservation efforts throughout the species range.
• The Resting Human Brain and Motor Learning
  - Curr Biol 19(12):1023-1027 (2009)
  Functionally related brain networks are engaged even in the absence of an overt behavior. The role of this resting state activity, evident as low-frequency fluctuations of BOLD (see [1] for review, [2], [3] and [4]) or electrical [5] and [6] signals, is unclear. Two major proposals are that resting state activity supports introspective thought or supports responses to future events [7]. An alternative perspective is that the resting brain actively and selectively processes previous experiences [8]. Here we show that motor learning can modulate subsequent activity within resting networks. BOLD signal was recorded during rest periods before and after an 11 min visuomotor training session. Motor learning but not motor performance modulated a fronto-parietal resting state network (RSN). Along with the fronto-parietal network, a cerebellar network not previously reported as an RSN was also specifically altered by learning. Both of these networks are engaged during learning o f similar visuomotor tasks [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21] and [22]. Thus, we provide the first description of the modulation of specific RSNs by prior learning—but not by prior performance—revealing a novel connection between the neuroplastic mechanisms of learning and resting state activity. Our approach may provide a powerful tool for exploration of the systems involved in memory consolidation.
• Decoding of Emotional Information in Voice-Sensitive Cortices
  - Curr Biol 19(12):1028-1033 (2009)
  The ability to correctly interpret emotional signals from others is crucial for successful social interaction. Previous neuroimaging studies showed that voice-sensitive auditory areas [1], [2] and [3] activate to a broad spectrum of vocally expressed emotions more than to neutral speech melody (prosody). However, this enhanced response occurs irrespective of the specific emotion category, making it impossible to distinguish different vocal emotions with conventional analyses [4], [5], [6], [7] and [8]. Here, we presented pseudowords spoken in five prosodic categories (anger, sadness, neutral, relief, joy) during event-related functional magnetic resonance imaging (fMRI), then employed multivariate pattern analysis [9] and [10] to discriminate between these categories on the basis of the spatial response pattern within the auditory cortex. Our results demonstrate successful decoding of vocal emotions from fMRI responses in bilateral voice-sensitive areas, which could not be obtained by using averaged response amplitudes only. Pairwise comparisons showed that each category could be classified against all other alternatives, indicating for each emotion a specific spatial signature that generalized across speakers. These results demonstrate for the first time that emotional information is represented by distinct spatial patterns that can be decoded from brain activity in modality-specific cortical areas.
• The Extracellular Domain of Smoothened Regulates Ciliary Localization and Is Required for High-Level Hh Signaling
  - Curr Biol 19(12):1034-1039 (2009)
  Members of the Hedgehog (Hh) family of secreted proteins function as morphogens to pattern developing tissues and control cell proliferation. The seven-transmembrane domain (7TM) protein Smoothened (Smo) is essential for the activation of all levels of Hh signaling. However, the mechanisms by which Smo differentially activates low- or high-level Hh signaling are not known [1]. Here we show that a newly identified mutation in the extracellular domain (ECD) of zebrafish Smo attenuates Smo signaling. The Smo agonist purmorphamine [2] induces the stabilization, ciliary translocation, and high-level signaling of wild-type Smo. In contrast, purmorphamine induces the stabilization but not the ciliary translocation or high-level signaling of the Smo ECD mutant protein. Surprisingly, a truncated form of Smo that lacks the cysteine-rich domain of the ECD localizes to the cilium but is unable to activate high-level Hh signaling. We also present evidence that cilia may be required for Hh signaling in early zebrafish embryos. These data indicate that the ECD, previously thought to be dispensable for vertebrate Smo function, both regulates Smo ciliary localization and is essential for high-level Hh signaling.
• The Relationship between Saccadic Suppression and Perceptual Stability
  - Curr Biol 19(12):1040-1043 (2009)
  Introspection makes it clear that we do not see the visual motion generated by our saccadic eye movements. We refer to the lack of awareness of the motion across the retina that is generated by a saccade as saccadic omission [1]: the visual stimulus generated by the saccade is omitted from our subjective awareness. In the laboratory, saccadic omission is often studied by investigating saccadic suppression, the reduction in visual sensitivity before and during a saccade (see Ross et al. [2] and Wurtz [3] for reviews). We investigated whether perceptual stability requires that a mechanism like saccadic suppression removes perisaccadic stimuli from visual processing to prevent their presumed harmful effect on perceptual stability [4] and [5]. Our results show that a stimulus that undergoes saccadic omission can nevertheless generate a shape contrast illusion. This illusion can be generated when the inducer and test stimulus are separated in space and is therefore thought t o be generated at a later stage of visual processing [6]. This shows that perceptual stability is attained without removing stimuli from processing and suggests a conceptually new view of perceptual stability in which perisaccadic stimuli are processed by the early visual system, but these signals are prevented from reaching awareness at a later stage of processing.
• Direct Tactile Stimulation of Dorsal Occipito-Temporal Cortex in a Visual Agnosic
  - Curr Biol 19(12):1044-1049 (2009)
  The human occipito-temporal cortex is preferentially activated by images of objects as opposed to scrambled images [1]. Touching objects (versus textures) also activates this region [2], [3], [4], [5], [6], [7], [8], [9] and [10]. We used neuropsychological fMRI to probe whether dorsal regions of the lateral occipital cortex (LO) are activated in tactile recognition without mediation through visual recognition. We tested a patient (HJA) with visual agnosia due to bilateral lesions of the ventral occipito-temporal cortex but spared dorsal LO. HJA's recognition of visual objects was impaired [11] and [12]. Nevertheless, his tactile recognition was preserved. We measured brain activity while participants viewed and touched objects and textures. There was overlapping activity in regions including LO and cerebellum for both stimuli for control participants, including new regions not before considered bimodal. For HJA, there were overlapping regions in the intact dorsal LO. W ithin a subset of the regions found in control participants, HJA showed activity only for tactile objects, suggesting that these regions are specifically involved in successful multimodal recognition. Activation of dorsal LO by tactile input is not secondary to visual recognition but can operate directly through tactile input.
• Retinoic Acid Promotes Limb Induction through Effects on Body Axis Extension but Is Unnecessary for Limb Patterning
  - Curr Biol 19(12):1050-1057 (2009)
  Retinoic acid (RA) is thought to be a key signaling molecule involved in limb bud patterning along the proximodistal or anteroposterior axes functioning through induction of Meis2 and Shh, respectively [1]. Here, we utilize Raldh2−/− and Raldh3−/− mouse embryos lacking RA synthesis [2] to demonstrate that RA signaling is not required for limb expression of Shh and Meis2. We demonstrate that RA action is required outside of the limb field in the body axis during forelimb induction but that RA is unnecessary at later stages when hindlimb budding and patterning occur. We provide evidence for a model of trunk mesodermal RA action in which forelimb induction requires RA repression of Fgf8 in the developing trunk similar to how RA controls somitogenesis [3] and [4] and heart development [5]. We demonstrate that pectoral fin development in RA-deficient zebrafish embryos can be rescued by an FGF receptor antagonist SU5402. In addition, embryo ChIP assays demonstrate tha t RA receptors bind the Fgf8 promoter in vivo. Our findings suggest that RA signaling is not required for limb proximodistal or anteroposterior patterning but that RA inhibition of FGF8 signaling during the early stages of body axis extension provides an environment permissive for induction of forelimb buds.
• Myosin-V Regulates oskar mRNA Localization in the Drosophila Oocyte
  - Curr Biol 19(12):1058-1063 (2009)
  Intracellular mRNA localization is an effective mechanism for protein targeting leading to functional polarization of the cell. The mechanisms controlling mRNA localization and specifically how the actin and microtubule (MT) cytoskeletons cooperate in this process are not well understood. In Drosophila, Oskar protein accumulation at the posterior pole of the oocyte is required for embryonic development [1], [2], [3] and [4] and is achieved by the transport of oskar mRNA and its exclusive translation at the posterior pole [1], [5], [6] and [7]. oskar mRNA localization requires the activity of the MT-based motor Kinesin [8], as well as the formation of a transport-competent ribonucleoprotein (RNP) complex [9]. Here, we show that didum, encoding the Drosophila actin-based motor Myosin-V [10] and [11], is a new posterior group gene that promotes posterior accumulation of Oskar. Myosin-V associates with the oskar mRNA transport complex preferentially at the oocyte cortex, re vealing a short-range actomyosin-based mechanism that mediates the local entrapment of oskar at the posterior pole. Our results also show that Myosin-V interacts with Kinesin heavy chain and counterbalances Kinesin function, preventing ectopic accumulation of oskar in the cytoplasm. Our findings reveal that a balance of microtubule- and actin-based motor activities regulates oskar mRNA localization in the Drosophila oocyte.
• Reduced Neural Integration of Letters and Speech Sounds Links Phonological and Reading Deficits in Adult Dyslexia
  - Curr Biol 19(12):1064 (2009)