Hot off the presses! Oct 26 curr biol

The Oct 26 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:

• Biodiversity crunch
  - curr biol 20(20):R863-R864 (2010)
  The current meeting in Nagoya of the UN Convention on Biological Diversity will be crucial for future conservation policies. Nigel Williams reports.
• Beefing it up
  - curr biol 20(20):R865-R866 (2010)
  A new study highlights the future environmental pressures of livestock production. Nigel Williams reports.
• Banking insights
  - curr biol 20(20):R866 (2010)
  After the recent crisis, bankers are increasingly looking to scientific advice. Nigel Williams reports.
• Marine catalogue of concern
  - curr biol 20(20):R867-R868 (2010)
  A 10-year study of marine organisms has provided an unprecedented list of species but highlights the worries about many of them. Nigel Williams reports.
• New ivory worries
  - curr biol 20(20):R869 (2010)
  
• David Fitch
  - curr biol 20(20):R869-R871 (2010)
  
• Atavisms
  - curr biol 20(20):R871 (2010)
  
• Infant cognition
  - curr biol 20(20):R872-R875 (2010)
  Until fairly recently, young infants were thought to be as cognitively incompetent as they were morally innocent. They were epistemological 'tabulae rasae', helpless 'bundles of reflexes' who spent all of their time sleeping, crying and sucking. In the famous words of William James, infants lived in "one great blooming, buzzing confusion".
• Multicellular development in a choanoflagellate
  - curr biol 20(20):R875-R876 (2010)
  Little is known about how the first animals evolved from their single-celled ancestors. Over 120 years ago, Ernst Haeckel proposed that animals evolved through "repeated self-division of [a] primary cell," [1] an idea supported by the observation that all animals develop from a single cell (the zygote) through successive rounds of cell division [2]. Nonetheless, there are multiple alternative hypotheses [3], including the formal possibility that multicellularity in the progenitor of animals occurred through cell aggregation, with embryogenesis by cell division being secondarily derived. The closest known relatives of animals, choanoflagellates, are emerging as a model system for testing specific hypotheses about animal origins [4], [5] and [6]. Studying colony formation in choanoflagellates may provide a context for reconstructing the evolution of animal multicellularity. Here, we find that the transition from single cells to multicellular colonies in the choanofla! gellate Salpingoeca rosetta (previously known as Proterospongia sp.) occurs by cell division, with sister cells remaining stably attached.
• Stable inheritance of an acquired behavior in Caenorhabditis elegans
  - curr biol 20(20):R877-R878 (2010)
  Sensory imprinting produces life-long attachment to environmental features experienced during a critical period of early development. Imprinting of this kind is highly conserved in evolution and is an important form of adaptive behavioral plasticity [1]. The nematode Caenorhabditis elegans undergoes such adaptation to new environments through imprinting: attractive odorants, when present during the first larval stage, produce life-long olfactory imprints that enhance attraction and egg-laying rates in the adults [2]. Here I report evidence that the olfactory imprint can be transmitted to the next generation. If the imprint is generated successively over more than four generations, it is not just transmitted through one further generation, but rather, it is stably inherited through many following generations. While the transient nature of the inheritance suggests the existence of resetting mechanisms, stable trans-generational inheritance of the kind reported here raise! s the possibility that a behavioral alteration produced by an environmental change might be genetically assimilated after a limited number of generations.
• Chromosome Segregation: Taking the Passenger Seat
  - curr biol 20(20):R879-R881 (2010)
  The chromosomal passenger complex (CPC) is a major regulator of mitotic and meiotic chromosome segregation. Three recent papers now elucidate the mechanisms that determine the localization of the CPC to the inner centromere.
• Decision Neuroscience: Choices of Description and of Experience
  - curr biol 20(20):R881-R883 (2010)
  A new study suggests that individuals differentially recruit neural regions associated with decision making, depending on whether the information about the options are learned through experience or merely described.
• Developmental Biology: A DOR Connecting Growth and Clocks
  - curr biol 20(20):R884-R886 (2010)
  DOR, a nuclear receptor co-activator conserved from flies to humans, provides a molecular connection between ecdysone and insulin signaling, two important pathways controlling developmental timing and growth, respectively.
• Gene Regulation: The Cohesin Ring Connects Developmental Highways
  - curr biol 20(20):R886-R888 (2010)
  How does cohesin regulate gene expression and development independently of its roles in sister chromatid cohesion and chromosome segregation? Recent studies show that cohesin, through multiple mechanisms, directly controls transcription of genes that regulate morphogenesis, differentiation, cell proliferation and pluripotency.
• Calcium Signalling: Fishing Out Molecules of Mitochondrial Calcium Transport
  - curr biol 20(20):R888-R891 (2010)
  Cellular energy metabolism, survival and death are controlled by mitochondrial calcium signals originating in the cytoplasm. Now, RNAi studies link three proteins — MICU1, NCLX and LETM1 — to the previously unknown molecular mechanism of mitochondrial calcium transport.
• Chemosensory Ecology: Deceiving Drosophila
  - curr biol 20(20):R891-R893 (2010)
  The Solomon's lily arum mimics the odours of yeast to attract drosophilid flies as unrewarded pollinators.
• Sensory Ecology: Night Lights Alter Reproductive Behavior of Blue Tits
  - curr biol 20(20):R893-R895 (2010)
  Research on songbirds indicates that streetlights influence timing of dawn chorus, egg-laying and male success in siring extra-pair young, providing new evidence that artificial lighting is an ecologically disruptive force.
• Actin Crosslinkers: Repairing the Sense of Touch
  - curr biol 20(20):R895-R896 (2010)
  Cells use actin bundles infused with myosin to exert contractile forces on the extracellular environment. This active tension is essential for cellular mechanosensation. Now, the role of actin crosslinkers in stabilizing and repairing the actin bundles is coming into clearer view.
• Optogenetic Approaches in Neuroscience
  - curr biol 20(20):R897-R903 (2010)
  The recently introduced term 'optogenetics' describes a variety of techniques for expressing genes in nerve cells that render them responsive to light. This approach makes use of light-sensitive channel proteins that can be used to manipulate neuronal function. Using genetic strategies, these channel proteins can be expressed in neurons defined by a common genetic identity, which can then be selectively activated or silenced through illumination. In this minireview, we shall describe the basic principles of such manipulative optogenetic approaches in neuroscience and summarize how these tools are being exploited to investigate neuronal circuits and behavior.
• A Direct Role for Cohesin in Gene Regulation and Ecdysone Response in Drosophila Salivary Glands
  - curr biol 20(20):1787-1798 (2010)
  Background Developmental abnormalities observed in Cornelia de Lange syndrome have been genetically linked to mutations in the cohesin machinery. These and other recent experimental findings have led to the suggestion that cohesin, in addition to its canonical function of mediating sister chromatid cohesion, might also be involved in regulating gene expression. Results We report that cleavage of cohesin's kleisin subunit in postmitotic Drosophila salivary glands induces major changes in the transcript levels of many genes. Kinetic analyses of changes in transcript levels upon cohesin cleavage reveal that a subset of genes responds to cohesin cleavage within a few hours. In addition, cohesin binds to most of these loci, suggesting that cohesin is directly regulating their expression. Among these genes are several that are regulated by the steroid hormone ecdysone. Cytological visualization of transcription at selected ecdysone-responsive genes reveals that puffing at Eip74EF ceases within an hour or two of cohesin cleavage, long before any decline in ecdysone receptor could be detected at this locus. Conclusion We conclude that cohesin regulates expression of a distinct set of genes, including those mediating the ecdysone response.
• dDOR Is an EcR Coactivator that Forms a Feed-Forward Loop Connecting Insulin and Ecdysone Signaling
  - curr biol 20(20):1799-1808 (2010)
  Background Mammalian DOR was discovered as a gene whose expression is misregulated in muscle of Zucker diabetic rats. Because no DOR loss-of-function mammalian models are available, we analyze here the in vivo function of DOR by studying flies mutant for Drosophila DOR (dDOR). Results We show that dDOR is a novel coactivator of ecdysone receptor (EcR) that is needed during metamorphosis. dDOR binds EcR and is required for maximal EcR transcriptional activity. In the absence of dDOR, flies display a number of ecdysone loss-of-function phenotypes such as impaired spiracle eversion, impaired salivary gland degradation, and pupal lethality. Furthermore, dDOR knockout flies are lean. We find that dDOR expression is inhibited by insulin signaling via FOXO. Conclusion This work uncovers dDOR as a novel EcR coactivator. It also establishes a mutual antagonistic relationship between ecdysone and insulin signaling in the fly fat body. Furthermore, because ecdysone signaling inhibits insulin signaling in the fat body, this also uncovers a feed-forward mechanism whereby ecdysone potentiates its own signaling via dDOR.
• Par3 Controls Epithelial Spindle Orientation by aPKC-Mediated Phosphorylation of Apical Pins
  - curr biol 20(20):1809-1818 (2010)
  Background Formation of epithelial sheets requires that cell division occurs in the plane of the sheet. During mitosis, spindle poles align so the astral microtubules contact the lateral cortex. Confinement of the mammalian Pins protein to the lateral cortex is essential for this process. Defects in signaling through Cdc42 and atypical protein kinase C (aPKC) also cause spindle misorientation. When epithelial cysts are grown in 3D cultures, misorientation creates multiple lumens. Results We now show that silencing of the polarity protein Par3 causes spindle misorientation in Madin-Darby canine kidney cell cysts. Silencing of Par3 also disrupts aPKC association with the apical cortex, but expression of an apically tethered aPKC rescues normal lumen formation. During mitosis, Pins is mislocalized to the apical surface in the absence of Par3 or by inhibition of aPKC. Active aPKC increases Pins phosphorylation on Ser401, which recruits 14-3-3 protein. 14-3-3 binding inhibits association of Pins with Gαi, through which Pins attaches to the cortex. A Pins S401A mutant mislocalizes over the cell cortex and causes spindle orientation and lumen defects. Conclusions The Par3 and aPKC polarity proteins ensure correct spindle pole orientation during epithelial cell division by excluding Pins from the apical cortex. Apical aPKC phosphorylates Pins, which results in the recruitment of 14-3-3 and inhibition of binding to Gαi, so the Pins falls off the cortex. In the absence of a functional exclusion mechanism, astral microtubules can associate with Pins over the entire epithelial cortex, resulting in randomized spindle pole orientation.
• Cooling the Thermal Grill Illusion through Self-Touch
  - curr biol 20(20):1819-1822 (2010)
  Acute peripheral pain is reduced by multisensory interactions at the spinal level [1]. Central pain is reduced by reorganization of cortical body representations [[2] and [3]]. We show here that acute pain can also be reduced by multisensory integration through self-touch, which provides proprioceptive, thermal, and tactile input forming a coherent body representation [[4] and [5]]. We combined self-touch with the thermal grill illusion (TGI) [6]. In the traditional TGI, participants press their fingers on two warm objects surrounding one cool object. The warm surround unmasks pain pathways, which paradoxically causes the cool object to feel painfully hot. Here, we warmed the index and ring fingers of each hand while cooling the middle fingers. Immediately after, these three fingers of the right hand were touched against the same three fingers on the left hand. This self-touch caused a dramatic 64% reduction in perceived heat. We show that this paradoxical release from! paradoxical heat cannot be explained by low-level touch-temperature interactions alone. To reduce pain, we often clutch a painful hand with the other hand. We show here that self-touch not only gates pain signals reaching the brain [[7], [8] and [9]] but also, via multisensory integration, increases coherence of cognitive body representations to which pain afferents project [10].
• Differentiable Neural Substrates for Learned and Described Value and Risk
  - curr biol 20(20):1823-1829 (2010)
  Studies of human decision making emerge from two dominant traditions: learning theorists [[1], [2] and [3]] study choices in which options are evaluated on the basis of experience, whereas behavioral economists and financial decision theorists study choices in which the key decision variables are explicitly stated. Growing behavioral evidence suggests that valuation based on these different classes of information involves separable mechanisms [[4], [5], [6], [7] and [8]], but the relevant neuronal substrates are unknown. This is important for understanding the all-too-common situation in which choices must be made between alternatives that involve one or another kind of information. We studied behavior and brain activity while subjects made decisions between risky financial options, in which the associated utilities were either learned or explicitly described. We show a characteristic effect in subjects' behavior when comparing information acquired from experience with! that acquired from description, suggesting that these kinds of information are treated differently. This behavioral effect was reflected neurally, and we show differential sensitivity to learned and described value and risk in brain regions commonly associated with reward processing. Our data indicate that, during decision making under risk, both behavior and the neural encoding of key decision variables are strongly influenced by the manner in which value information is presented.
• A Simple Rule Reduces Costs of Extragroup Parasitism in a Communally Breeding Bird
  - curr biol 20(20):1830-1833 (2010)
  How do cooperatively breeding groups resist invasion by parasitic "cheaters," which dump their eggs in the communal nest but provide no parental care [[1] and [2]]? Here I show that Greater Anis (Crotophaga major), Neotropical cuckoos that nest in social groups containing several breeding females [3], use a simple rule based on the timing of laying to recognize and reject eggs laid by extragroup parasites. I experimentally confirmed that Greater Anis cannot recognize parasitic eggs based on the appearance of host egg phenotypes or on the number of eggs in the clutch. However, they can discriminate between freshly laid eggs and those that have already been incubated, and they accordingly eject asynchronous eggs. This mechanism is reliable in naturally parasitized nests, because group members typically lay their eggs in tight synchrony, whereas the majority of parasitic eggs are laid several days later. Rejection of asynchronous eggs therefore provides a rare empiric! al example of a complex, group-level behavior that arises through relatively simple "rules of thumb" without requiring advanced cognitive mechanisms such as learning, counting, or individual recognition.
• Cetaceans on a Molecular Fast Track to Ultrasonic Hearing
  - curr biol 20(20):1834-1839 (2010)
  The early radiation of cetaceans coincides with the origin of their defining ecological and sensory differences [[1] and [2]]. Toothed whales (Odontoceti) evolved echolocation for hunting 36–34 million years ago, whereas baleen whales (Mysticeti) evolved filter feeding and do not echolocate [2]. Echolocation in toothed whales demands exceptional high-frequency hearing [3], and both echolocation and ultrasonic hearing have also evolved independently in bats [[4] and [5]]. The motor protein Prestin that drives the electromotility of the outer hair cells (OHCs) is likely to be especially important in ultrasonic hearing, because it is the vibratory response of OHC to incoming sound waves that confers the enhanced sensitivity and selectivity of the mammalian auditory system [[6] and [7]]. Prestin underwent adaptive change early in mammal evolution [8] and also shows sequence convergence between bats and dolphins [[9] and [10]], as well as within bats [11]. Focusing on wha! les, we show for the first time that the extent of protein evolution in Prestin can be linked directly to the evolution of high-frequency hearing. Moreover, we find that independent cases of sequence convergence in mammals have involved numerous identical amino acid site replacements. Our findings shed new light on the importance of Prestin in the evolution of mammalian hearing.
• Cse1l Is a Negative Regulator of CFTR-Dependent Fluid Secretion
  - curr biol 20(20):1840-1845 (2010)
  Transport of chloride through the cystic fibrosis transmembrane conductance regulator (CFTR) channel is a key step in regulating fluid secretion in vertebrates [[1] and [2]]. Loss of CFTR function leads to cystic fibrosis [[1], [3] and [4]], a disease that affects the lungs, pancreas, liver, intestine, and vas deferens. Conversely, uncontrolled activation of the channel leads to increased fluid secretion and plays a major role in several diseases and conditions including cholera [[5] and [6]] and other secretory diarrheas [7] as well as polycystic kidney disease [[8], [9] and [10]]. Understanding how CFTR activity is regulated in vivo has been limited by the lack of a genetic model. Here, we used a forward genetic approach in zebrafish to uncover CFTR regulators. We report the identification, isolation, and characterization of a mutation in the zebrafish cse1l gene that leads to the sudden and dramatic expansion of the gut tube. We show that this phenotype results from! a rapid accumulation of fluid due to the uncontrolled activation of the CFTR channel. Analyses in zebrafish larvae and mammalian cells indicate that Cse1l is a negative regulator of CFTR-dependent fluid secretion. This work demonstrates the importance of fluid homeostasis in development and establishes the zebrafish as a much-needed model system to study CFTR regulation in vivo.
• A Deceptive Pollination System Targeting Drosophilids through Olfactory Mimicry of Yeast
  - curr biol 20(20):1846-1852 (2010)
  In deceptive pollination, insects are bamboozled into performing nonrewarded pollination. A prerequisite for the evolutionary stability in such systems is that the plants manage to generate a perfect sensory impression of a desirable object in the insect nervous system [1]. The study of these plants can provide important insights into sensory preference of their visiting insects. Here, we present the first description of a deceptive pollination system that specifically targets drosophilid flies. We show that the examined plant (Arum palaestinum) accomplishes its deception through olfactory mimicry of fermentation, a strategy that represents a novel pollination syndrome. The lily odor is composed of volatiles characteristic of yeast, and produces in Drosophila melanogaster an antennal detection pattern similar to that elicited by a range of fermentation products. By functional imaging, we show that the lily odors target a specific subset of odorant receptors (ORs), whic! h include the most conserved OR genes in the drosophilid olfactome. Furthermore, seven of eight visiting drosophilid species show a congruent olfactory response pattern to the lily, in spite of comprising species pairs separated by 40 million years [2], showing that the lily targets a basal function of the fly nose, shared by species with similar ecological preference.
• Keeping Cell Identity in Arabidopsis Requires PRC1 RING-Finger Homologs that Catalyze H2A Monoubiquitination
  - curr biol 20(20):1853-1859 (2010)
  Polycomb group (PcG) proteins form conserved regulatory complexes that modify chromatin to repress the genes that are not required in a specific differentiation status [1]. In animals, the two best-characterized PcG complexes are PRC2 and PRC1, which respectively possess histone 3 lysine 27 (H3K27) trimethyltransferase [[2], [3] and [4]] and histone 2A lysine 119 (H2AK119) E3 ubiquitin ligase activities [[5], [6] and [7]]. In Arabidopsis, PRC2 activity is also required for the gene silencing mechanism [8]; however, the existence of PRC1 has been questioned, because plant genomes do not encode clear PRC1 components and H2A monoubiquitination has not been detected [[6] and [9]]. Conversely, recent reports have unveiled the presence of homologs to PRC1 components that together with plant-specific proteins could be part of the long-sought PRC1-like complexes [[10] and [11]]. Here we show that the PRC1 RING-finger homologs AtBMI1A and AtBMI1B are implicated in the repressio! n of embryonic and stem cell regulators. Plants impaired in AtBMI1A and AtBMI1B show derepression of embryonic traits in somatic cells, displaying a phenotype similar to plants mutant in PRC2 components [[12], [13] and [14]]. Our data demonstrate that the AtBMI1A/B proteins mediate H2A monoubiquitination in Arabidopsis and that this mark, together with PRC2-mediated H3K27 trimethylation, plays a key role in maintaining cell identity.
• Learning to Use an Invisible Visual Signal for Perception
  - curr biol 20(20):1860-1863 (2010)
  How does the brain construct a percept from sensory signals? One approach to this fundamental question is to investigate perceptual learning as induced by exposure to statistical regularities in sensory signals [[1], [2], [3], [4], [5], [6] and [7]]. Recent studies showed that exposure to novel correlations between sensory signals can cause a signal to have new perceptual effects [[2] and [3]]. In those studies, however, the signals were clearly visible. The automaticity of the learning was therefore difficult to determine. Here we investigate whether learning of this sort, which causes new effects on appearance, can be low level and automatic by employing a visual signal whose perceptual consequences were made invisible—a vertical disparity gradient masked by other depth cues. This approach excluded high-level influences such as attention or consciousness. Our stimulus for probing perceptual appearance was a rotating cylinder. During exposure, we introduced a new co! ntingency between the invisible signal and the rotation direction of the cylinder. When subsequently presenting an ambiguously rotating version of the cylinder, we found that the invisible signal influenced the perceived rotation direction. This demonstrates that perception can rapidly undergo "structure learning" by automatically picking up novel contingencies between sensory signals, thus automatically recruiting signals for novel uses during the construction of a percept.
• Effectively Reducing Sensory Eye Dominance with a Push-Pull Perceptual Learning Protocol
  - curr biol 20(20):1864-1868 (2010)
  Much knowledge of sensory cortical plasticity is gleaned from perceptual learning studies that improve visual performance [[1], [2], [3], [4], [5], [6] and [7]]. Although the improvements are likely caused by modifications of excitatory and inhibitory neural networks, most studies were not primarily designed to differentiate their relative contributions. Here we designed a novel push-pull training protocol to reduce sensory eye dominance (SED), a condition that is mainly caused by unbalanced interocular inhibition [[8], [9] and [10]]. During the training, an attention cue presented to the weak eye precedes the binocular competitive stimulation. The cue stimulates the weak eye (push) while causing interocular inhibition of the strong eye (pull). We found that this push-pull protocol reduces SED (shifts the balance toward the weak eye) and improves stereopsis more so than the push-only protocol, which solely stimulates the weak eye without inhibiting the strong eye. The ! stronger learning effect with the push-pull training than the push-only training underscores the crucial involvement of a putative inhibitory mechanism in sensory plasticity. The design principle of the push-pull protocol can potentially lend itself as an effective, noninvasive treatment of amblyopia.
• Encoding of Motor Skill in the Corticomuscular System of Musicians
  - curr biol 20(20):1869-1874 (2010)
  How motor skills are stored in the nervous system represents a fundamental question in neuroscience. Although musical motor skills are associated with a variety of adaptations [[1], [2] and [3]], it remains unclear how these changes are linked to the known superior motor performance of expert musicians. Here we establish a direct and specific relationship between the functional organization of the corticomuscular system and skilled musical performance. Principal component analysis was used to identify joint correlation patterns in finger movements evoked by transcranial magnetic stimulation over the primary motor cortex while subjects were at rest. Linear combinations of a selected subset of these patterns were used to reconstruct active instrumental playing or grasping movements. Reconstruction quality of instrumental playing was superior in skilled musicians compared to musically untrained subjects, displayed taxonomic specificity for the trained movement repertoire,! and correlated with the cumulated long-term training exposure, but not with the recent past training history. In violinists, the reconstruction quality of grasping movements correlated negatively with the long-term training history of violin playing. Our results indicate that experience-dependent motor skills are specifically encoded in the functional organization of the primary motor cortex and its efferent system and are consistent with a model of skill coding by a modular neuronal architecture [4].
• LIN-14 Inhibition of LIN-12 Contributes to Precision and Timing of C. elegans Vulval Fate Patterning
  - curr biol 20(20):1875-1879 (2010)
  Studies of C. elegans vulval development have illuminated mechanisms underlying cell fate specification and elucidated intercellular signaling pathways [1]. The vulval precursor cells (VPCs) are spatially patterned during the L3 stage by the EGFR-Ras-MAPK-mediated inductive signal and the LIN-12/Notch-mediated lateral signal. The pattern is both precise and robust [2] because of crosstalk between these pathways [3]. Signaling is also regulated temporally, because constitutive activation of the spatial patterning pathways does not alter the timing of VPC fate specification [[4] and [5]]. The heterochronic genes, including the microRNA lin-4 and its target lin-14, constitute a temporal control mechanism used in different contexts [[6], [7] and [8]]. We find that lin-4 specifically controls the activity of LIN-12/Notch through lin-14, but not other known targets, and that persistent lin-14 blocks LIN-12 activity without interfering with the key events of LIN-12/Notch sign! al transduction. In the L2 stage, there is sufficient lin-14 activity to inhibit constitutive lin-12. Our results suggest that lin-4 and lin-14 contribute to spatial patterning through temporal gating of LIN-12. We propose that in the L2 stage, lin-14 sets a high threshold for LIN-12 activation to help prevent premature activation of LIN-12 by ligands expressed in other cells in the vicinity, thereby contributing to the precision and robustness of VPC fate patterning.