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Current Biology: CB

Geng-Yuan Chen, Joseph M Cleary, Ana B Asenjo, Yalei Chen, Jacob A Mascaro, David F J Arginteanu, Hernando Sosa, William O Hancock
Besides sliding apart antiparallel microtubules during spindle elongation, the mitotic kinesin-5, Eg5, promotes microtubule polymerization, emphasizing its importance in mitotic spindle length control. Here, we characterize the Eg5 microtubule polymerase mechanism by assessing motor-induced changes in the longitudinal and lateral tubulin-tubulin bonds that form the microtubule lattice. Isolated Eg5 motor domains promote microtubule nucleation, growth, and stability; thus, crosslinking tubulin by pairs of motor heads is not necessary for polymerase activity...
June 29, 2019: Current Biology: CB
Miao Tian, Kazufumi Mochizuki, Josef Loidl
To preserve genome integrity, eukaryotic cells use small RNA-directed mechanisms to repress transposable elements (TEs). Paradoxically, in order to silence TEs, precursors of the small RNAs must be transcribed from TEs. However, it is still poorly understood how these precursors are transcribed from TEs under silenced conditions. In the otherwise transcriptionally silent germline micronucleus (MIC) of Tetrahymena, a burst of non-coding RNA (ncRNA) transcription occurs during meiosis. The transcripts are processed into small RNAs that serve to identify TE-related sequences for elimination...
June 28, 2019: Current Biology: CB
Jyoti Garg, Alejandro Saettone, Syed Nabeel-Shah, Matthew Cadorin, Marcelo Ponce, Susanna Marquez, Shuye Pu, Jack Greenblatt, Jean-Philippe Lambert, Ronald E Pearlman, Jeffrey Fillingham
Mediator is a large protein complex required for basal and regulated expression of most RNA polymerase II (RNAP II)-transcribed genes, in part due to its interaction with and phosphorylation of the conserved C-terminal domain (CTD) of Rpb1 [1, 2]. Mediator has been implicated in many aspects of gene expression including chromatin looping [3], higher-order chromatin folding [4], mRNA processing [5] and export [6], and transcriptional memory [7]. Mediator is thought to have played a major role during eukaryotic diversification [8, 9], although its function remains unknown in evolutionarily deep branching eukaryotes lacking canonical CTD heptad repeats...
June 28, 2019: Current Biology: CB
Ioanna Leontiou, Nitobe London, Karen M May, Yingrui Ma, Lucile Grzesiak, Bethan Medina-Pritchard, Priya Amin, A Arockia Jeyaprakash, Sue Biggins, Kevin G Hardwick
The spindle checkpoint monitors kinetochore-microtubule interactions and generates a "wait anaphase" delay when any defects are apparent [1-3]. This provides time for cells to correct chromosome attachment errors and ensure high-fidelity chromosome segregation. Checkpoint signals are generated at unattached chromosomes during mitosis. To activate the checkpoint, Mps1Mph1 kinase phosphorylates the kinetochore component KNL1Spc105/Spc7 on conserved MELT motifs to recruit Bub3-Bub1 complexes [4-6] via a direct Bub3 interaction with phospho-MELT motifs [7, 8]...
June 24, 2019: Current Biology: CB
José M Ramos-Sánchez, Paolo M Triozzi, Daniel Alique, Feng Geng, Mingjun Gao, Katja E Jaeger, Philip A Wigge, Isabel Allona, Mariano Perales
Day length is a key indicator of seasonal information that determines major patterns of behavior in plants and animals. Photoperiodism has been described in plants for about 100 years, but the underlying molecular mechanisms of day length perception and signal transduction in many systems are not well understood. In trees, photoperiod perception plays a major role in growth cessation during the autumn as well as activating the resumption of shoot growth in the spring, both processes controlled by FLOWERING LOCUS T2 (FT2) expression levels and critical for the survival of perennial plants over winter [1-4]...
June 24, 2019: Current Biology: CB
Yang Liu, Margarita Ramos-Womack, Clair Han, Patrick Reilly, Kelly LaRue Brackett, William Rogers, Thomas M Williams, Peter Andolfatto, David L Stern, Mark Rebeiz
Hox genes pattern the anterior-posterior axis of animals and are posited to drive animal body plan evolution, yet their precise role in evolution has been difficult to determine. Here, we identified evolutionary modifications in the Hox gene Abd-B that dramatically altered its expression along the body plan of Drosophila santomea. Abd-B is required for pigmentation in Drosophila yakuba, the sister species of D. santomea, and changes to Abd-B expression would be predicted to make large contributions to the loss of body pigmentation in D...
June 21, 2019: Current Biology: CB
Molly Z Liu, Leslie B Vosshall
Female Aedes aegypti mosquitoes use multiple sensory modalities to hunt human hosts and obtain a blood meal for egg production. Attractive cues include carbon dioxide (CO2 ), a major component of exhaled breath [1, 2]; heat elevated above ambient temperature, signifying warm-blooded skin [3, 4]; and dark visual contrast [5, 6], proposed to bridge long-range olfactory and short-range thermal cues [7]. Any of these sensory cues in isolation is an incomplete signal of a human host, and so a mosquito must integrate multimodal sensory information before committing to approaching and biting a person [8]...
June 20, 2019: Current Biology: CB
Juan Chen, Irene Sperandio, Molly J Henry, Melvyn A Goodale
Our visual system provides a distance-invariant percept of object size by integrating retinal image size with viewing distance (size constancy). Single-unit studies with animals have shown that some distance cues, especially oculomotor cues such as vergence and accommodation, can modulate the signals in the thalamus or V1 at the initial processing stage [1-7]. Accordingly, one might predict that size constancy emerges much earlier in time [8-10], even as visual signals are being processed in the thalamus. So far, the studies that have looked directly at size coding have either used fMRI (poor temporal resolution [11-13]) or relied on inadequate stimuli (pictorial illusions presented on a monitor at a fixed distance [11, 12, 14, 15])...
June 19, 2019: Current Biology: CB
Keegan M Melstrom, Randall B Irmis
Extinct crocodyliforms from the age of dinosaurs (Mesozoic Era) display an impressive range of skeletal morphologies, suggesting a diversity of ecological roles not found in living representatives [1-6]. In particular, unusual dental morphologies develop repeatedly through the evolutionary history of this group [2, 4-9]. Recent descriptions of fossil crocodyliforms and their unusual teeth provide the inferential basis for a wide range of feeding ecologies. However, tests of these hypotheses are hindered by the lack of directly comparable dental morphologies in living reptiles and mammals, thereby preventing an accurate ecosystem reconstruction...
June 19, 2019: Current Biology: CB
Dongjun He, Yingying Wang, Fang Fang
Crowding, the identification difficulty for a target in the presence of nearby flankers, is an essential bottleneck for object recognition and visual awareness [1, 2]. As suggested by multitudes of behavioral studies, crowding occurs because the visual system lacks the necessary resolution (e.g., small receptive field or high resolution of spatial attention) to isolate the target from flankers and therefore integrates them mistakenly [3-12]. However, this idea has rarely been tested with neuroscience methods directly...
June 18, 2019: Current Biology: CB
Olga V Alekseyenko, Yick-Bun Chan, Benjamin W Okaty, YoonJeung Chang, Susan M Dymecki, Edward A Kravitz
Pathological aggression is commonly associated with psychiatric and neurological disorders and can impose a substantial burden and cost on human society. Serotonin (5HT) has long been implicated in the regulation of aggression in a wide variety of animal species. In Drosophila, a small group of serotonergic neurons selectively modulates the escalation of aggression. Here, we identified downstream targets of serotonergic input-two types of neurons with opposing roles in aggression control. The dendritic fields of both neurons converge on a single optic glomerulus LC12, suggesting a key pathway linking visual input to the aggression circuitry...
June 18, 2019: Current Biology: CB
Marc Krasovec, Yusuke Kazama, Kotaro Ishii, Tomoko Abe, Dmitry A Filatov
The loss of functional genes from non-recombining sex-specific chromosomes [1, 2], such as the Y chromosomes in mammals [3] or W chromosomes in birds [4], should result in an imbalance of gene products for sex-linked genes [5]. Different chromosome-wide systems that rebalance gene expression are known to operate in organisms with relatively old sex chromosomes [6]; e.g., Drosophila overexpress X-linked genes in males [7], while mammals shut down one of the X chromosomes in females [8]. It is not known how long it takes for a chromosome-wide dosage compensation system to evolve...
June 14, 2019: Current Biology: CB
Amanda L Stansbury, Vincent M Janik
Vocal production learning is a rare communication skill and has only been found in selected avian and mammalian species [1-4]. Although humans use learned formants and voiceless sounds to encode most lexical information [5], evidence for vocal learning in other animals tends to focus on the modulation pattern of the fundamental frequency [3, 4]. Attempts to teach mammals to produce human speech sounds have largely been unsuccessful, most notably in extensive studies on great apes [5]. The limited evidence for formant copying in mammals raises the question whether advanced learned control over formant production is uniquely human...
June 14, 2019: Current Biology: CB
James M Jordan, Jonathan D Hibshman, Amy K Webster, Rebecca E W Kaplan, Abigail Leinroth, Ryan Guzman, Colin S Maxwell, Rojin Chitrakar, Elizabeth Anne Bowman, Amanda L Fry, E Jane Albert Hubbard, L Ryan Baugh
The roundworm C. elegans reversibly arrests larval development during starvation [1], but extended early-life starvation reduces reproductive success [2, 3]. Maternal dietary restriction (DR) buffers progeny from starvation as young larvae, preserving reproductive success [4]. However, the developmental basis of reduced fertility following early-life starvation is unknown, and it is unclear how maternal diet modifies developmental physiology in progeny. We show here that extended starvation in first-stage (L1) larvae followed by unrestricted feeding results in a variety of developmental abnormalities in the reproductive system, including proliferative germ-cell tumors and uterine masses that express neuronal and epidermal cell fate markers...
June 13, 2019: Current Biology: CB
Ashley J Thomas, Barbara W Sarnecka
For humans and other social species, social status matters: it determines who wins access to contested resources, territory, and mates [1-11]. Human infants are sensitive to dominance status cues [12, 13]. They expect conflicts to be won by larger individuals [14], those with more allies [15], and those with a history of winning [16-18]. But being sensitive to status cues is not enough; individuals must also use status information when deciding whom to approach and whom to avoid [19]. In many non-human species, low-status individuals avoid high-status individuals and in so doing avoid the threat of aggression [20-23]...
June 11, 2019: Current Biology: CB
Jonathan T Perelmuter, Anthony B Wilson, Joseph A Sisneros, Paul M Forlano
Dopamine is integral to attentional and motivational processes, but studies are largely restricted to the central nervous system. In mammals [1, 2] and fishes [3, 4], central dopaminergic neurons project to the inner ear and could modulate acoustic signals at the earliest stages of processing. Studies in rodents show dopamine inhibits cochlear afferent neurons and protects against noise-induced acoustic injury [5-10]. However, other functions for inner ear dopamine have not been investigated, and the effect of dopamine on peripheral auditory processing in non-mammalians remains unknown [11, 12]...
June 10, 2019: Current Biology: CB
Scott Schlossberg, Michael J Chase, Robert Sutcliffe
Botswana holds roughly one-third of Africa's remaining savannah elephants (Loxodonta africana) [1, 2] and will play a key role in the future conservation of this species. To date, Botswana has been one of the safest countries for elephants, with little poaching reported [3]. Here, we present evidence of a new outbreak of elephant poaching for ivory in northern Botswana. Comparing results from 2014 and 2018 aerial surveys, we found that elephant populations were stable, but numbers of elephant carcasses have increased, especially for newer carcasses dead for less than roughly 1 year...
June 10, 2019: Current Biology: CB
Jonathon Hannabuss, Manuel Lera-Ramirez, Nicholas I Cade, Franck J Fourniol, François Nédélec, Thomas Surrey
In anaphase spindles, antiparallel microtubules associate to form tight midzone bundles, as required for functional spindle architecture and correct chromosome segregation. Several proteins selectively bind to these overlaps to control cytokinesis. How midzone bundles assemble is poorly understood. Here, using an in vitro reconstitution approach, we demonstrate that minimal midzone bundles can reliably self-organize in solution from dynamic microtubules, the microtubule crosslinker PRC1, and the motor protein KIF4A...
June 7, 2019: Current Biology: CB
Chih-Yang Chen, Klaus-Peter Hoffmann, Claudia Distler, Ziad M Hafed
A defining feature of the primate visual system is its foveated nature. Processing of foveal retinal input is important not only for high-quality visual scene analysis but also for ensuring precise, albeit tiny, gaze shifts during high-acuity visual tasks. The representations of foveal retinal input in the primate lateral geniculate nucleus and early visual cortices have been characterized. However, how such representations translate into precise eye movements remains unclear. Here, we document functional and structural properties of the foveal visual representation of the midbrain superior colliculus...
June 6, 2019: Current Biology: CB
Preetham Ganupuru, Adam B Goldring, Rashed Harun, Timothy D Hanks
To understand the neural mechanisms that support decision making, it is critical to characterize the timescale of evidence evaluation. Recent work has shown that subjects can adaptively adjust the timescale of evidence evaluation across blocks of trials depending on context [1]. However, it's currently unknown if adjustments to evidence evaluation occur online during deliberations based on a single stream of evidence. To examine this question, we employed a change-detection task in which subjects report their level of confidence in judging whether there has been a change in a stochastic auditory stimulus...
June 5, 2019: Current Biology: CB
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