Bio-Med Roundup

This month in Bio-Med Roundup:
  • King-Casas et al. investigated the neural mechanisms underlying the breakdown of cooperative behavior in patients with borderline personality disorder.
  • Gardner et al. reported how a rare cell type in peripheral lymphoid tissues may act as a safety net in eliminating autoreactive immune cells.
  • Wang et al. and Vásquez et al. shed light on the gating mechanism of the bacterial mechanosensitive ion channel, MscS.
  • Dimos et al. showed that induced pluripotent stem cells generated from patients with ALS can be differentiated into motor neurons.
  • Brouns et al. described a bacterial defense system based on small RNA molecules that match short sequences in phage DNA.
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BIOCHEMISTRY
 
Evidence of Global Chlorophyll d (1 August 2008)
Y. Kashiyama et al.
A survey of chlorophyll d, used by a cyanobacterium for harvesting infrared light, implies that this microbe inhabits a much wider range than previously thought.

Crystal Structure of the Termination Module of a Nonribosomal Peptide Synthetase (1 August 2008)
A. Tanovic, S. A. Samel, L.-O. Essen, M. A. Marahiel
A large enzyme complex assembles peptide natural products without ribosomal participation by successive catalytic steps at the end of a flexible, substrate-loaded arm.

The Crystal Structure of a Sodium Galactose Transporter Reveals Mechanistic Insights into Na+/Sugar Symport (8 August 2008)
S. Faham et al.
The structure of a sugar transporter suggests how these proteins may rearrange to permit the sugar to enter and leave the binding site on opposite sides of the membrane.
See related Perspective.

The Structure of an Open Form of an E. coli Mechanosensitive Channel at 3.45 Å Resolution (29 August 2008)
W. Wang et al.
Circularly arrayed transmembrane helices in the bacterial mechanosensitive ion channel, MscS, expand like the iris of a camera to open the channel and allow ion efflux.
See related Perspective.

Solution Structure of the Integral Human Membrane Protein VDAC-1 in Detergent Micelles (29 August 2008)
S. Hiller et al.
A channel that allows diffusion of metabolites across the mitochondrial outer membrane forms an unusual 19-stranded β barrel with a pore size of about 25 angstroms.

A Structural Mechanism for MscS Gating in Lipid Bilayers (29 August 2008)
V. Vásquez, M. Sotomayor, J. Cordero-Morales, K. Schulten, E. Perozo
Electron paramagnetic resonance measurements reveal that tilting of transmembrane helices facilitates the opening of a bacterial mechanosensitive channel in a lipid bilayer.
See related Perspective.


IMMUNOLOGY

Regulation of CD45 Alternative Splicing by Heterogeneous Ribonucleoprotein, hnRNPLL (1 August 2008)
S. Oberdoerffer et al.
A ribonucleoprotein directs the splicing of the transcript for CD45, a transmembrane tyrosine phosphatase that initiates signaling through antigen receptors.
See related Perspective.

Pyogenic Bacterial Infections in Humans with MyD88 Deficiency (1 August 2008)
H. von Bernuth et al.
Although a key immune gene is necessary for mice to fight off a broad range of pathogens, in humans it is only required to protect against a few specialized bacteria.

Censoring of Autoreactive B Cell Development by the Pre-B Cell Receptor (1 August 2008)
R. A. Keenan et al.
A protein that helps newly rearranged antibody chains arrive at the cell surface of immature immune cells is found to help delete cells with potential autoreactivity.

Deletional Tolerance Mediated by Extrathymic Aire-Expressing Cells (8 August 2008)
J. M. Gardner et al.
Cells in the spleen and lymph nodes express self-antigens to detect and remove circulating self-reactive immune cells that have escaped deletion by the thymus.
See related Perspective.

In Vivo Imaging Reveals an Essential Role for Neutrophils in Leishmaniasis Transmitted by Sand Flies (15 August 2008)
N. C. Peters et al.
Visualization of the area around a bite from a parasite-infected sand fly shows that the first immune cells to arrive engulf and unexpectedly protect the invading parasite.
See related Perspective.

Variability and Robustness in T Cell Activation from Regulated Heterogeneity in Protein Levels (22 August 2008)
O. Feinerman, J. Veiga, J. R. Dorfman, R. N. Germain, G. Altan-Bonnet
Variations in component levels of the antigen-induced signaling pathway affect the final response of activated immune cells, conferring flexibility on the system.


NEUROSCIENCE/PSYCHOLOGY

The Cell and Molecular Basis of Mechanical, Cold, and Inflammatory Pain (1 August 2008)
B. Abrahamsen et al.
Pain neurons containing a particular sodium channel respond only to cold, mechanical, and inflammatory pain, not to all painful stimuli as previously assumed.

The Rupture and Repair of Cooperation in Borderline Personality Disorder (8 August 2008)
B. King-Casas et al.
In a game, patients with personality disorder cannot build trust with normal partners, possibly because they cannot distinguish between trusting and distrusting acts in others.
See related Perspective.

Dichotomous Dopaminergic Control of Striatal Synaptic Plasticity (8 August 2008)
W. Shen, M. Flajolet, P. Greengard, D. J. Surmeier
Contrary to previous assumptions, dopamine helps both strengthen and weaken synapses made by cortical cells onto cells of the subcortical striatum.

Dynamic Shifts of Limited Working Memory Resources in Human Vision (8 August 2008)
P. M. Bays and M. Husain
Working memory is a flexibly allocated, but finite, resource; more attention given to an object means it is remembered more precisely, whereas other objects are remembered less well.

The Contribution of Single Synapses to Sensory Representation in Vivo (15 August 2008)
A. Arenz, R. A. Silver, A. T. Schaefer, T. W. Margrie
Only 100 synapses are required to accurately code for the animals’ velocity in the mouse cerebellum; the charge transfer into neurons is linearly related to acceleration.

Grueneberg Ganglion Cells Mediate Alarm Pheromone Detection in Mice (22 August 2008)
J. Brechbühl, M. Klaey, M.-C. Broillet
A mysterious ganglion at the tip of the nose is an olfactory subsystem that senses alarm pheromones in mice.

Automatic Mental Associations Predict Future Choices of Undecided Decision-Makers (22 August 2008)
S. Galdi, L. Arcuri, B. Gawronski
Unexpectedly, consciously expressed voting choices predict later unconscious preferences, showing that unconscious and conscious cognition is a two-way street.
See related Perspective.

Amyloid-β Dynamics Correlate with Neurological Status in the Injured Human Brain (29 August 2008)
D. L. Brody et al.
After brain injury of normal people, the amount of an Alzheimer’s disease peptide decreases in the extracellular fluid of the brain, returning to normal with recovery.


CELL/DEVELOPMENTAL BIOLOGY

Essential Cytoplasmic Translocation of a Cytokine Receptor–Assembled Signaling Complex (1 August 2008)
A. Matsuzawa et al.
Degradation of one member of a protein complex that forms when a cytokine receptor is activated causes the complex to move to the cytoplasm, triggering the downstream pathway.
See related Perspective.

Generation of Pluripotent Stem Cells from Adult Mouse Liver and Stomach Cells (1 August 2008)
T. Aoi et al.
Induced pluripotent stem cells are generated by direct reprogramming of adult liver and stomach cells.

Control of the Reversibility of Cellular Quiescence by the Transcriptional Repressor HES1 (22 August 2008)
L. Sang, H. A. Coller, J. M. Roberts
For quiescent cells to periodically divide and then rest, a member of the Notch signaling pathway HES1 must be present; this protein is also activated in some tumors.

Induced Pluripotent Stem Cells Generated from Patients with ALS Can Be Differentiated into Motor Neurons (29 August 2008)
J. T. Dimos et al.
Skin cells from elderly individuals with a mutation that causes amyotrophic lateral sclerosis (ALS) were used to derive stem cells that could then be differentiated.
See related Perspective.


MOLECULAR BIOLOGY
 
A Global View of Gene Activity and Alternative Splicing by Deep Sequencing of the Human Transcriptome (15 August 2008)
M. Sultan et al.
Shotgun sequencing of 27–base pair segments of messenger RNA from human kidney and immune cells identifies previously undescribed transcriptional units and splice functions.

Small CRISPR RNAs Guide Antiviral Defense in Prokaryotes (15 August 2008)
S. J. J. Brouns et al.
Some bacterial genomes contain remnant sequences from previous viral infections, which are transcribed into RNA to guide inactivation of the virus in subsequent infections.
See related Perspective.

Suppression of the MicroRNA Pathway by Bacterial Effector Proteins (15 August 2008)
L. Navarro, F. Jay, K. Nomura, S. Y. He, O. Voinnet
Upon bacterial infection, Arabidopsis mounts a microRNA-mediated innate immune defense, which is inhibited by proteins of the bacteria, allowing other infections.

Heterochromatin Integrity Affects Chromosome Reorganization After Centromere Dysfunction (22 August 2008)
K. Ishii et al.
When the centromere is removed from a yeast chromosome, a new one forms near the end of the chromosome, over a cluster of poorly expressed genes.


MICROBIOLOGY/VIROLOGY

The Global Stoichiometry of Litter Nitrogen Mineralization (1 August 2008)
S. Manzoni, R. B. Jackson, J. A. Trofymow, A. Porporato
A global data set shows that the decomposition rate of plant litter is primarily controlled by its nitrogen content, which affects the rate of microbial activity.

Arsenic(III) Fuels Anoxygenic Photosynthesis in Hot Spring Biofilms from Mono Lake, California (15 August 2008)
T. R. Kulp et al.
A primitive form of photosynthesis in which arsenic is the electron donor occurs in purple bacteria in a California lake, perhaps a relic of early life forms.

Targeting QseC Signaling and Virulence for Antibiotic Development (22 August 2008)
D. A. Rasko et al.
A small, nontoxic antibiotic candidate interferes with bacterial detection of the host and inhibits infection, in a therapeutic approach that may avoid development of resistance.

Adenovirus Small e1a Alters Global Patterns of Histone Modification (22 August 2008)
G. A. Horwitz et al.
Epigenetic Reprogramming by Adenovirus e1a (22 August 2008)
R. Ferrari et al.
Upon infection, an adenovirus protein causes global epigenetic changes in the host that repress antiviral responses and differentiation and activate cell-cycle genes.

Redox-Active Antibiotics Control Gene Expression and Community Behavior in Divergent Bacteria (29 August 2008)
L. E. P. Dietrich, T. K. Teal, A. Price-Whelan, D. K. Newman
In addition to an antiseptic function, phenazines—pigmented antibiotics made by bacteria—organize colony structure by activating a superoxidative stress regulator.


MEDICINE

Human CHN1 Mutations Hyperactivate α2-Chimaerin and Cause Duane’s Retraction Syndrome (8 August 2008)
N. Miyake et al.
A signaling protein that helps nerve fibers find their correct target muscles is required for innervation of the eye muscles and, if defective, causes an eye movement disorder.

Tumor Regression in Cancer Patients by Very Low Doses of a T Cell–Engaging Antibody (15 August 2008)
R. Bargou et al.
Tested in a small group of patients, a therapeutic antibody binds to both tumor cells and immune cells, increasing the local concentration and effectiveness of the immune cells.


PLANT SCIENCE

A Conserved Mutation in an Ethylene Biosynthesis Enzyme Leads to Andromonoecy in Melons (8 August 2008)
A. Boualem et al.
Melon plants have both hermaphroditic and male flowers, a mating system that results from a mutation involved in ethylene synthesis that is still under positive selection.

Plant Immunity Requires Conformational Charges of NPR1 via S-Nitrosylation and Thioredoxins (15 August 2008)
Y. Tada et al.
After a pathogen invades a plant, a protein, usually kept in a multimeric state by S-nitrosylation, is dissociated by thioredoxin, freeing the monomers for defense responses.

Field Experiments with Transformed Plants Reveal the Sense of Floral Scents (29 August 2008)
D. Kessler, K. Gase, I. T. Baldwin
Genetic manipulation of wild tobacco plants balances the use of scent to attract pollinators and toxin to limit nectar consumption in order to optimize reproduction.
See related Perspective.