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Current Biology
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Nov 20, 2012

Volume 22Issue 22p2087-2188, R933-R980
Open Archive
On the cover: The adult penis worm Priapulus caudatus (Priapulida) (anterior is to the top; the posterior end bears a caudal appendage). Bilaterally symmetrical animals are divided into deuterostomes and protostomes, traditionally based on whether the blastopore gives rise to the anus or the mouth, respectively. In this issue, Martín-Durán et al. (pages 2161–2166) show that the protostome penis worms, related to arthropods and nematodes, develop like deuterostome animals, such as sea urchins or vertebrates, significantly changing our understanding of the evolution of bilateral animals. Image by Mattias Ormestad....
On the cover: The adult penis worm Priapulus caudatus (Priapulida) (anterior is to the top; the posterior end bears a caudal appendage). Bilaterally symmetrical animals are divided into deuterostomes and protostomes, traditionally based on whether the blastopore gives rise to the anus or the mouth, respectively. In this issue, Martín-Durán et al. (pages 2161–2166) show that the protostome penis worms, related to arthropods and nematodes, develop like deuterostome animals, such as sea urchins or vertebrates, significantly changing our understanding of the evolution of bilateral animals. Image by Mattias Ormestad.

Magazine

Feature

  • How does an animal work?

    • Michael Gross
    A newly established interdisciplinary research institute in Lyon, France, aims to bridge the cultural divides between evolution, development, and physiology, in order to study how animal functions come into being, starting from the genomes, and not limited to traditional model systems. Michael Gross reports.

Q & A

  • Christophe Boesch

    • Christophe Boesch
    Born in St. Gall, Switzerland, Christophe Boesch spent his early childhood in that city and moved to Paris at the age of 8 to finish his primary and secondary school. He moved to Geneva in 1968 where he completed his diploma of biology. He began working on chimpanzees in the Taï forest in Côte d’Ivoire in 1979. Since 1998, he is a director at the Max Planck Institute of Evolutionary Anthropology in Leipzig, Germany. His work on the evolution of chimpanzee culture has been synthesised in his recent book Wild Cultures: A Comparison between Chimpanzee and Human Cultures.

Quick guide

  • Monopolin

    • Dannel McCollum
    What is monopolin and how did it get its name? Monopolin is a protein complex that organizes chromosomal architecture at the centromere and the ribosomal DNA (rDNA) repeats. Monopolin was identified in Saccharomyces cerevisiae as a core complex (Csm1 and Lrs4) and two accessory proteins (Mam1 and Hrr25) that is required for reductional division of chromosomes during meiosis I. Unlike mitosis, during meiosis I, sister chromatid pairs align at the metaphase plate with their homologous chromosome pair, and then each sister pair segregates together to opposite poles.

Primer

  • Place, space and memory cells

    • Elizabeth Marozzi,
    • Kathryn J. Jeffery
    Self-localization and navigation are critical functions for the survival of mobile animals. By processing sensory information such as landmarks and environmental features, as well as keeping track of the path they have taken, animals are able to remain oriented as they explore the world, learning what resources are where and planning how to reach them. This ancient capacity for self-orientation has, through evolution, become intimately entwined with the ability to remember the events of daily life — an ability known as episodic memory.

Correspondence

  • 21 years of shelf life between discovery and description of new species

    • Benoît Fontaine,
    • Adrien Perrard,
    • Philippe Bouchet
    A large part of biodiversity is still unknown, and it is estimated that, at the current pace, it will take several centuries to describe all species living on Earth. In the context of the ongoing ‘sixth extinction’, accelerating the completion of the inventory of living biota is an issue that reaches far beyond the taxonomic community. However, the factors that influence the accretion of known species remain poorly understood. Here, we study how long it takes from the first collection of a specimen of a new species to its formal description and naming in the scientific literature [1,2] — a period we refer to as a species’ ‘shelf life’.

Dispatches

  • Sleep Biology: Tuning In While Tuned Out

    • Jimmy Fraigne,
    • John Peever
    The barrel cortex and whisker thalamus preferentially respond to whisker movements during REM sleep in infant rats. Understanding why the brain tunes into sensory signals while it’s tuned out in sleep may provide clues about the functions of REM sleep.
  • Aging: Evolution of Life Span Revisited

    • Damian K. Dowling
    A new study reports that high rates of extrinsic mortality can lead to the evolution of a longer life — a pattern opposite to that expected under the classic predictions of the evolutionary theory of aging.
  • Dopamine: On the Threshold of Sleep

    • Pavel Masek,
    • Alex C. Keene
    A new study examining the neural circuitry regulating sleep in Drosophila has identified a pair of dopamine neurons that signal to the fan-shaped body to suppress sleep. These neurons are separate from the dopamine neurons that regulate motivation, memory, and feeding, suggesting that independent populations of dopamine neurons regulate distinct behaviors.
  • Histones: Sequestered by Jabba in Fatty Storehouse

    • William F. Marzluff,
    • Deirdre C. Tatomer
    A paper in this issue shows that histones H2a and H2b are stored in lipid droplets in Drosophila embryos complexed with the protein Jabba. In Jabba mutant embryos, histones H2a and H2b are degraded but embryos survive by translating stored histone mRNA.
  • Sexual Attraction: Sex-Specific Wiring of Neural Circuitry

    • E. Paxon Frady,
    • Christopher R. Palmer,
    • William B. Kristan Jr.
    Two recent studies describe mechanisms by which sexually dimorphic responses to pheromones in the nematode worm Caenorhabditis elegans are driven by differences in the balance of neural circuits that control attraction and repulsion behaviors.
  • Evolution: Cichlid Models on the Runaway to Speciation

    • Hugo F. Gante,
    • Walter Salzburger
    Rapid speciation has fascinated biologists for a long time. A recent study shows that ecological opportunity and sex-biased color differences increase the likelihood of speciation in African cichlid fishes.
  • Cell Biology: Cohesin Ring Exit Gate Revealed

    • Yuya Yamagishi,
    • Yoshinori Watanabe
    A multiprotein complex called cohesin mediates sister chromatid cohesion by entrapping sister DNAs into a tripartite ring. Recent studies show that Wapl opens the newly identified DNA exit gate of the cohesin ring, only when Smc3 is deacetylated, and that mutations in human Smc3 deacetylase cause a developmental disorder.
  • Transcription: Base J Blocks the Way

    • Dane Z. Hazelbaker,
    • Stephen Buratowski
    How do cells stop transcribing RNA Polymerase II to promote proper gene expression and prevent transcriptional havoc in the genome? In the case of Leishmania, a uniquely modified DNA base blocks RNA Polymerase II and suggests an interesting new model for transcription termination.
  • Organelle Biogenesis: En BLOC Exchange for RAB32 and RAB38

    • Michael S. Marks
    Prominent subtypes of the genetic disorder Hermansky–Pudlak syndrome result from defects in a mysterious protein complex, BLOC-3. New work identifies BLOC-3 as a guanine nucleotide exchange factor for two RAB GTPases previously implicated in lysosome-related organelle biogenesis.

Review

  • The Spindle Assembly Checkpoint

    • Pablo Lara-Gonzalez,
    • Frederick G. Westhorpe,
    • Stephen S. Taylor
    During mitosis and meiosis, the spindle assembly checkpoint acts to maintain genome stability by delaying cell division until accurate chromosome segregation can be guaranteed. Accuracy requires that chromosomes become correctly attached to the microtubule spindle apparatus via their kinetochores. When not correctly attached to the spindle, kinetochores activate the spindle assembly checkpoint network, which in turn blocks cell cycle progression. Once all kinetochores become stably attached to the spindle, the checkpoint is inactivated, which alleviates the cell cycle block and thus allows chromosome segregation and cell division to proceed.

Articles

  • Localized Tensional Forces on PECAM-1 Elicit a Global Mechanotransduction Response via the Integrin-RhoA Pathway

    • Caitlin Collins,
    • Christophe Guilluy,
    • Christopher Welch,
    • E. Timothy O’Brien,
    • Klaus Hahn,
    • Richard Superfine,
    • Keith Burridge,
    • Ellie Tzima
    Mechanical forces regulate cell behavior and function during development, differentiation, and tissue morphogenesis. In the vascular system, forces produced by blood flow are critical determinants not only of morphogenesis and function, but also of pathological states such as atherosclerosis. Endothelial cells (ECs) have numerous mechanotransducers, including platelet endothelial cell adhesion molecule-1 (PECAM-1) at cell-cell junctions and integrins at cell-matrix adhesions. However, the processes by which forces are transduced to biochemical signals and subsequently translated into downstream effects are poorly understood.
  • Neuronal Circuits Underlying Persistent Representations Despite Time Varying Activity

    • Shaul Druckmann,
    • Dmitri B. Chklovskii
    Our brains are capable of remarkably stable stimulus representations despite time-varying neural activity. For instance, during delay periods in working memory tasks, while stimuli are represented in working memory, neurons in the prefrontal cortex, thought to support the memory representation, exhibit time-varying neuronal activity. Since neuronal activity encodes the stimulus, its time-varying dynamics appears to be paradoxical and incompatible with stable network stimulus representations. Indeed, this finding raises a fundamental question: can stable representations only be encoded with stable neural activity, or, its corollary, is every change in activity a sign of change in stimulus representation?
  • Lipid Droplets Control the Maternal Histone Supply of Drosophila Embryos

    • Zhihuan Li,
    • Katharina Thiel,
    • Peter J. Thul,
    • Mathias Beller,
    • Ronald P. Kühnlein,
    • Michael A. Welte
    Histones are essential for chromatin packing, yet free histones not incorporated into chromatin are toxic. While in most cells multiple regulatory mechanisms prevent accumulation of excess histones, early Drosophila embryos contain massive extranuclear histone stores, thought to be essential for development. Excess histones H2A, H2B, and H2Av are bound to lipid droplets, ubiquitous fat storage organelles especially abundant in embryos. It has been proposed that sequestration on lipid droplets allows safe transient storage of supernumerary histones.
  • Two Dopaminergic Neurons Signal to the Dorsal Fan-Shaped Body to Promote Wakefulness in Drosophila

    • Qili Liu,
    • Sha Liu,
    • Lay Kodama,
    • Maria R. Driscoll,
    • Mark N. Wu
    The neuronal circuitry underlying sleep is poorly understood. Although dopamine (DA) is thought to play a key role in sleep/wake regulation, the identities of the individual DA neurons and their downstream targets required for this process are unknown.
  • Dendritic Filopodia, Ripped Pocket, NOMPC, and NMDARs Contribute to the Sense of Touch in Drosophila Larvae

    • Asako Tsubouchi,
    • Jason C. Caldwell,
    • W. Daniel Tracey
    Among the Aristotelian senses, the subcellular and molecular mechanisms involved in the sense of touch are the most poorly understood.

Reports

  • BLOC-3 Mutated in Hermansky-Pudlak Syndrome Is a Rab32/38 Guanine Nucleotide Exchange Factor

    • Andreas Gerondopoulos,
    • Lars Langemeyer,
    • Jin-Rui Liang,
    • Andrea Linford,
    • Francis A. Barr
    Hermansky-Pudlak syndrome (HPS) is a human disease characterized by partial loss of pigmentation and impaired blood clotting [1–3]. These symptoms are caused by defects in the biogenesis of melanosomes and platelet dense granules, often referred to as lysosome-related organelles [2]. Genes mutated in HPS encode subunits of the biogenesis of lysosome-related organelles complexes (BLOCs). BLOC-1 and BLOC-2, together with the AP-3 clathrin adaptor complex, act at early endosomes to sort components required for melanin formation and melanosome biogenesis away from the degradative lysosomal pathway toward early stage melanosomes [4–6].
  • Longer Life Span Evolves under High Rates of Condition-Dependent Mortality

    • Hwei-yen Chen,
    • Alexei A. Maklakov
    Aging affects nearly all organisms, but how aging evolves is still unclear [1–5]. The central prediction of classic theory is that high extrinsic mortality leads to accelerated aging and shorter intrinsic life span [6, 7]. However, this prediction considers mortality as a random process, whereas mortality in nature is likely to be condition dependent. Therefore, the novel theory maintains that condition dependence may dramatically alter, and even reverse, the classic pattern [2–4]. We present experimental evidence for the evolution of longer life span under high condition-dependent mortality.
  • An Asian Elephant Imitates Human Speech

    • Angela S. Stoeger,
    • Daniel Mietchen,
    • Sukhun Oh,
    • Shermin de Silva,
    • Christian T. Herbst,
    • Soowhan Kwon,
    • W. Tecumseh Fitch
    Vocal imitation has convergently evolved in many species, allowing learning and cultural transmission of complex, conspecific sounds, as in birdsong [1, 2]. Scattered instances also exist of vocal imitation across species, including mockingbirds imitating other species or parrots and mynahs producing human speech [3, 4]. Here, we document a male Asian elephant (Elephas maximus) that imitates human speech, matching Korean formants and fundamental frequency in such detail that Korean native speakers can readily understand and transcribe the imitations.
  • The First Stalk-Eyed Phosphatocopine Crustacean from the Lower Cambrian of China

    • Xi-guang Zhang,
    • Brian R. Pratt
    Exhibiting Orsten-type preservation, specimens of the phosphatocopine Dabashanella sp. from the Lower Cambrian Stage 3 (about 520 million years ago) of southern China possess a single-fold shield and a set of appendages of crustacean design. More significantly, a pair of stalked eyes—the earliest known visual structure in this group—is attached to an ocular segment analogous to the anterior sclerite of various stem-group arthropods [1, 2]. Accordingly, a unique visual system must have been present among some, if not all, early phosphatocopines.
  • Embryonic Learning of Vocal Passwords in Superb Fairy-Wrens Reveals Intruder Cuckoo Nestlings

    • Diane Colombelli-Négrel,
    • Mark E. Hauber,
    • Jeremy Robertson,
    • Frank J. Sulloway,
    • Herbert Hoi,
    • Matteo Griggio,
    • Sonia Kleindorfer
    How do parents recognize their offspring when the cost of making a recognition error is high [1–3]? Avian brood parasite-host systems have been used to address this question because of the high cost of parasitism to host fitness. We discovered that superb fairy-wren (Malurus cyaneus) females call to their eggs, and upon hatching, nestlings produce begging calls with key elements from their mother’s “incubation call.” Cross-fostering experiments showed highest similarity between foster mother and nestling calls, intermediate similarity with genetic mothers, and least similarity with parasitic Horsfield's bronze-cuckoo (Chalcites basalis) nestlings.
  • Deuterostomic Development in the Protostome Priapulus caudatus

    • José M. Martín-Durán,
    • Ralf Janssen,
    • Sofia Wennberg,
    • Graham E. Budd,
    • Andreas Hejnol
    The fate of the blastopore during development in the bilaterian ancestor is currently not well understood. In deuterostomes, the blastopore forms the anus, but its fate in protostome groups is variable [1]. This variability, combined with an absence of information from key taxa, hampers the reconstruction of the ancestral developmental mode of the Protostomia and the Bilateria. The blastopore fate of the bilaterian ancestor plays a crucial role in understanding the transition from radial to bilateral symmetric organisms [2, 3].
  • Simplification and Desexualization of Gene Expression in Self-Fertile Nematodes

    • Cristel G. Thomas,
    • Renhua Li,
    • Harold E. Smith,
    • Gavin C. Woodruff,
    • Brian Oliver,
    • Eric S. Haag
    Evolutionary transitions between sexual modes could be potent forces in genome evolution [1, 2]. Several Caenorhabditis nematode species have evolved self-fertile hermaphrodites from the obligately outcrossing females of their ancestors [3]. We explored the relationship between sexual mode and global gene expression by comparing two selfing species, C. elegans and C. briggsae, with three phylogenetically informative outcrossing relatives, C. remanei, C. brenneri, and C. japonica. Adult transcriptome assemblies from the selfing species are consistently and strikingly smaller than those of the outcrossing species.
  • Organelle Size Equalization by a Constitutive Process

    • William B. Ludington,
    • Linda Z. Shi,
    • Qingyuan Zhu,
    • Michael W. Berns,
    • Wallace F. Marshall
    How cells control organelle size is an elusive problem. Two predominant models for size control can be distinguished: (1) induced control, where organelle genesis, maintenance, and disassembly are three separate programs that are activated in response to size change [1, 2], and (2) constitutive control, where stable size results from the balance between continuous organelle assembly and disassembly [3, 4]. The problem has been studied in Chlamydomonas reinhardtii because the flagella are easy to measure, their size changes only in the length dimension, and the genetics are comparable to yeast [5].
  • Substrate-Borne Vibratory Communication during Courtship in Drosophila melanogaster

    • Caroline C.G. Fabre,
    • Berthold Hedwig,
    • Graham Conduit,
    • Peter A. Lawrence,
    • Stephen F. Goodwin,
    • José Casal
    Courtship in Drosophila melanogaster has become an iconic example of an innate and interactive series of behaviors [1–11]. The female signals her acceptance of copulation by becoming immobile in response to a male's display of stereotyped actions. The male and female communicate via vision, air-borne sounds, and pheromones [1, 2], but what triggers the female's immobility is undetermined. Here, we describe an overlooked and important component of Drosophila courtship. Video recordings and laser vibrometry show that the male abdomen shakes (“quivers”), generating substrate-borne vibrations at about six pulses per second.

Erratum

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