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Syria, slums, and health security

2017-04-27T10:26:36-07:00




News at a glance

2017-04-27T10:26:36-07:00




An unprecedented march for science

2017-04-27T10:26:36-07:00




Meet the science marchers

2017-04-27T10:26:36-07:00
















The vaccine wars

2017-04-27T10:26:36-07:00




The science of persuasion

2017-04-27T10:26:36-07:00




Vaccine myths

2017-04-27T10:26:36-07:00




Vaccines on trial

2017-04-27T10:26:36-07:00




The natural capital of city trees

2017-04-27T10:26:36-07:00







Linking stem cells to germ cells

2017-04-27T10:26:36-07:00




Extracting the contents of living cells

2017-04-27T10:26:36-07:00




H. Boyd Woodruff (1917-2017)

2017-04-27T10:26:36-07:00







What lies beneath

2017-04-27T10:26:36-07:00




A state of denial

2017-04-27T10:26:36-07:00







Mexico's invasive species plan in context

2017-04-27T10:26:36-07:00




Community network for deaf scientists

2017-04-27T10:26:36-07:00




Nature's treasure hunt

2017-04-27T10:26:36-07:00




Bridges, not walls?

2017-04-27T10:26:36-07:00







Forum's fight for science

2017-04-27T10:26:36-07:00




Aspiring to do better than one's parents

2017-04-27T10:26:36-07:00




Pattern formation in the brain

2017-04-27T10:26:36-07:00




Getting phosphorus into healthy shape

2017-04-27T10:26:36-07:00




Taking a look at fungal bioluminescence

2017-04-27T10:26:36-07:00




Imaging an atomic soliton train

2017-04-27T10:26:36-07:00




Zinc can compete with lithium

2017-04-27T10:26:36-07:00




Ancient genomics of horse domestication

2017-04-27T10:26:36-07:00




Sensitive and specific CRISPR diagnostics

2017-04-27T10:26:36-07:00




Thinking local about building

2017-04-27T10:26:36-07:00




Single-cell diversity in the brain

2017-04-27T10:26:36-07:00




Germ cells on demand

2017-04-27T10:26:36-07:00




An old cancer drug's degrading new look

2017-04-27T10:26:36-07:00




Solar heat helps harvest humidity

2017-04-27T10:26:36-07:00




Using quasar pairs to measure smoothness

2017-04-27T10:26:36-07:00




When forces depend on orientation

2017-04-27T10:26:36-07:00




Plant the right tree

2017-04-27T10:26:36-07:00




Interferon-independent antiviral defense

2017-04-27T10:26:36-07:00










A privileged status for animate objects

2017-04-27T10:26:36-07:00




The making of the human brain

2017-04-27T10:26:36-07:00




Planning for a rise

2017-04-27T10:26:36-07:00




Menstrual cycle on a chip

2017-04-27T10:26:36-07:00




Rise on the rise

2017-04-27T10:26:36-07:00




Delaying demise

2017-04-27T10:26:36-07:00




Virtues of splitting up water-splitting

2017-04-27T10:26:36-07:00




The fading American dream: Trends in absolute income mobility since 1940

2017-04-27T10:26:36-07:00

We estimated rates of "absolute income mobility"—the fraction of children who earn more than their parents—by combining data from U.S. Census and Current Population Survey cross sections with panel data from de-identified tax records. We found that rates of absolute mobility have fallen from approximately 90% for children born in 1940 to 50% for children born in the 1980s. Increasing Gross Domestic Product (GDP) growth rates alone cannot restore absolute mobility to the rates experienced by children born in the 1940s. However, distributing current GDP growth more equally across income groups as in the 1940 birth cohort would reverse more than 70% of the decline in mobility. These results imply that reviving the "American dream" of high rates of absolute mobility would require economic growth that is shared more broadly across the income distribution.




Pcdh{alpha}c2 is required for axonal tiling and assembly of serotonergic circuitries in mice

2017-04-27T10:26:36-07:00

Serotonergic neurons project their axons pervasively throughout the brain and innervate various target fields in a space-filling manner, leading to tiled arrangements of their axon terminals to allow optimal allocation of serotonin among target neurons. Here we show that conditional deletion of the mouse protocadherin α (Pcdhα) gene cluster in serotonergic neurons disrupts local axonal tiling and global assembly of serotonergic circuitries and results in depression-like behaviors. Genetic dissection and expression profiling revealed that this role is specifically mediated by Pcdhαc2, which is the only Pcdhα isoform expressed in serotonergic neurons. We conclude that, in contrast to neurite self-avoidance, which requires single-cell identity mediated by Pcdh diversity, a single cell-type identity mediated by the common C-type Pcdh isoform is required for axonal tiling and assembly of serotonergic circuitries.




Multicluster Pcdh diversity is required for mouse olfactory neural circuit assembly

2017-04-27T10:26:36-07:00

The vertebrate clustered protocadherin (Pcdh) cell surface proteins are encoded by three closely linked gene clusters (Pcdhα, Pcdhβ, and Pcdh). Here, we show that all three gene clusters functionally cooperate to provide individual mouse olfactory sensory neurons (OSNs) with the cell surface diversity required for their assembly into distinct glomeruli in the olfactory bulb. Although deletion of individual Pcdh clusters had subtle phenotypic consequences, the loss of all three clusters (tricluster deletion) led to a severe axonal arborization defect and loss of self-avoidance. By contrast, when endogenous Pcdh diversity is overridden by the expression of a single–tricluster gene repertoire (α and β and ), OSN axons fail to converge to form glomeruli, likely owing to contact-mediated repulsion between axons expressing identical combinations of Pcdh isoforms.




Rechargeable nickel-3D zinc batteries: An energy-dense, safer alternative to lithium-ion

2017-04-27T10:26:36-07:00

The next generation of high-performance batteries should include alternative chemistries that are inherently safer to operate than nonaqueous lithium-based batteries. Aqueous zinc-based batteries can answer that challenge because monolithic zinc sponge anodes can be cycled in nickel–zinc alkaline cells hundreds to thousands of times without undergoing passivation or macroscale dendrite formation. We demonstrate that the three-dimensional (3D) zinc form-factor elevates the performance of nickel–zinc alkaline cells in three fields of use: (i) >90% theoretical depth of discharge (DODZn) in primary (single-use) cells, (ii) >100 high-rate cycles at 40% DODZn at lithium-ion–commensurate specific energy, and (iii) the tens of thousands of power-demanding duty cycles required for start-stop microhybrid vehicles.




Measurement of the small-scale structure of the intergalactic medium using close quasar pairs

2017-04-27T10:26:36-07:00

The distribution of diffuse gas in the intergalactic medium (IGM) imprints a series of hydrogen absorption lines on the spectra of distant background quasars known as the Lyman-α forest. Cosmological hydrodynamical simulations predict that IGM density fluctuations are suppressed below a characteristic scale where thermal pressure balances gravity. We measured this pressure-smoothing scale by quantifying absorption correlations in a sample of close quasar pairs. We compared our measurements to hydrodynamical simulations, where pressure smoothing is determined by the integrated thermal history of the IGM. Our findings are consistent with standard models for photoionization heating by the ultraviolet radiation backgrounds that reionized the universe.




Formation of matter-wave soliton trains by modulational instability

2017-04-27T10:26:36-07:00

Nonlinear systems can exhibit a rich set of dynamics that are inherently sensitive to their initial conditions. One such example is modulational instability, which is believed to be one of the most prevalent instabilities in nature. By exploiting a shallow zero-crossing of a Feshbach resonance, we characterize modulational instability and its role in the formation of matter-wave soliton trains from a Bose-Einstein condensate. We examine the universal scaling laws exhibited by the system and, through real-time imaging, address a long-standing question of whether the solitons in trains are created with effectively repulsive nearest-neighbor interactions or rather evolve into such a structure.




A multifunctional catalyst that stereoselectively assembles prodrugs

2017-04-27T10:26:36-07:00

The catalytic stereoselective synthesis of compounds with chiral phosphorus centers remains an unsolved problem. State-of-the-art methods rely on resolution or stoichiometric chiral auxiliaries. Phosphoramidate prodrugs are a critical component of pronucleotide (ProTide) therapies used in the treatment of viral disease and cancer. Here we describe the development of a catalytic stereoselective method for the installation of phosphorus-stereogenic phosphoramidates to nucleosides through a dynamic stereoselective process. Detailed mechanistic studies and computational modeling led to the rational design of a multifunctional catalyst that enables stereoselectivity as high as 99:1.




Water harvesting from air with metal-organic frameworks powered by natural sunlight

2017-04-27T10:26:36-07:00

Atmospheric water is a resource equivalent to ~10% of all fresh water in lakes on Earth. However, an efficient process for capturing and delivering water from air, especially at low humidity levels (down to 20%), has not been developed. We report the design and demonstration of a device based on a porous metal-organic framework {MOF-801, [Zr6O4(OH)4(fumarate)6]} that captures water from the atmosphere at ambient conditions by using low-grade heat from natural sunlight at a flux of less than 1 sun (1 kilowatt per square meter). This device is capable of harvesting 2.8 liters of water per kilogram of MOF daily at relative humidity levels as low as 20% and requires no additional input of energy.




Direction-specific van der Waals attraction between rutile TiO2 nanocrystals

2017-04-27T10:26:36-07:00

Mutual lattice orientations dictate the types and magnitudes of forces between crystalline particles. When lattice polarizability is anisotropic, the van der Waals dispersion attraction can, in principle, contribute to this direction dependence. We report measurement of this attraction between rutile nanocrystals, as a function of their mutual orientation and surface hydration extent. At tens of nanometers of separation, the attraction is weak and shows no dependence on azimuthal alignment or surface hydration. At separations of approximately one hydration layer, the attraction is strongly dependent on azimuthal alignment and systematically decreases as intervening water density increases. Measured forces closely agree with predictions from Lifshitz theory and show that dispersion forces can generate a torque between particles interacting in solution and between grains in materials.




Nucleic acid detection with CRISPR-Cas13a/C2c2

2017-04-27T10:26:36-07:00

Rapid, inexpensive, and sensitive nucleic acid detection may aid point-of-care pathogen detection, genotyping, and disease monitoring. The RNA-guided, RNA-targeting clustered regularly interspaced short palindromic repeats (CRISPR) effector Cas13a (previously known as C2c2) exhibits a "collateral effect" of promiscuous ribonuclease activity upon target recognition. We combine the collateral effect of Cas13a with isothermal amplification to establish a CRISPR-based diagnostic (CRISPR-Dx), providing rapid DNA or RNA detection with attomolar sensitivity and single-base mismatch specificity. We use this Cas13a-based molecular detection platform, termed Specific High-Sensitivity Enzymatic Reporter UnLOCKing (SHERLOCK), to detect specific strains of Zika and Dengue virus, distinguish pathogenic bacteria, genotype human DNA, and identify mutations in cell-free tumor DNA. Furthermore, SHERLOCK reaction reagents can be lyophilized for cold-chain independence and long-term storage and be readily reconstituted on paper for field applications.




Ancient genomic changes associated with domestication of the horse

2017-04-27T10:26:36-07:00

The genomic changes underlying both early and late stages of horse domestication remain largely unknown. We examined the genomes of 14 early domestic horses from the Bronze and Iron Ages, dating to between ~4.1 and 2.3 thousand years before present. We find early domestication selection patterns supporting the neural crest hypothesis, which provides a unified developmental origin for common domestic traits. Within the past 2.3 thousand years, horses lost genetic diversity and archaic DNA tracts introgressed from a now-extinct lineage. They accumulated deleterious mutations later than expected under the cost-of-domestication hypothesis, probably because of breeding from limited numbers of stallions. We also reveal that Iron Age Scythian steppe nomads implemented breeding strategies involving no detectable inbreeding and selection for coat-color variation and robust forelimbs.




New Products

2017-04-27T10:26:36-07:00







Standing up to fear

2017-04-27T10:26:36-07:00




Intersection of diverse neuronal genomes and neuropsychiatric disease: The Brain Somatic Mosaicism Network

2017-04-27T10:26:36-07:00

Neuropsychiatric disorders have a complex genetic architecture. Human genetic population-based studies have identified numerous heritable sequence and structural genomic variants associated with susceptibility to neuropsychiatric disease. However, these germline variants do not fully account for disease risk. During brain development, progenitor cells undergo billions of cell divisions to generate the ~80 billion neurons in the brain. The failure to accurately repair DNA damage arising during replication, transcription, and cellular metabolism amid this dramatic cellular expansion can lead to somatic mutations. Somatic mutations that alter subsets of neuronal transcriptomes and proteomes can, in turn, affect cell proliferation and survival and lead to neurodevelopmental disorders. The long life span of individual neurons and the direct relationship between neural circuits and behavior suggest that somatic mutations in small populations of neurons can significantly affect individual neurodevelopment. The Brain Somatic Mosaicism Network has been founded to study somatic mosaicism both in neurotypical human brains and in the context of complex neuropsychiatric disorders.




Anticancer sulfonamides target splicing by inducing RBM39 degradation via recruitment to DCAF15

2017-04-27T10:26:36-07:00

Indisulam is an aryl sulfonamide drug with selective anticancer activity. Its mechanism of action and the basis for its selectivity have so far been unknown. Here we show that indisulam promotes the recruitment of RBM39 (RNA binding motif protein 39) to the CUL4-DCAF15 E3 ubiquitin ligase, leading to RBM39 polyubiquitination and proteasomal degradation. Mutations in RBM39 that prevent its recruitment to CUL4-DCAF15 increase RBM39 stability and confer resistance to indisulam’s cytotoxicity. RBM39 associates with precursor messenger RNA (pre-mRNA) splicing factors, and inactivation of RBM39 by indisulam causes aberrant pre-mRNA splicing. Many cancer cell lines derived from hematopoietic and lymphoid lineages are sensitive to indisulam, and their sensitivity correlates with DCAF15 expression levels. Two other clinically tested sulfonamides, tasisulam and chloroquinoxaline sulfonamide, share the same mechanism of action as indisulam. We propose that DCAF15 expression may be a useful biomarker to guide clinical trials of this class of drugs, which we refer to as SPLAMs (splicing inhibitor sulfonamides).




RETINOBLASTOMA RELATED1 mediates germline entry in Arabidopsis

2017-04-27T10:26:36-07:00

To produce seeds, flowering plants need to specify somatic cells to undergo meiosis. Here, we reveal a regulatory cascade that controls the entry into meiosis starting with a group of redundantly acting cyclin-dependent kinase (CDK) inhibitors of the KIP-RELATED PROTEIN (KRP) class. KRPs function by restricting CDKA;1–dependent inactivation of the Arabidopsis Retinoblastoma homolog RBR1. In rbr1 and krp triple mutants, designated meiocytes undergo several mitotic divisions, resulting in the formation of supernumerary meiocytes that give rise to multiple reproductive units per future seed. One function of RBR1 is the direct repression of the stem cell factor WUSCHEL (WUS), which ectopically accumulates in meiocytes of triple krp and rbr1 mutants. Depleting WUS in rbr1 mutants restored the formation of only a single meiocyte.