Structural basis of substrate recognition by a polypeptide processing and secretion transporter
The peptidase-containing ATP-binding cassette transporters (PCATs) are unique members of the ABC transporter family that proteolytically process and export peptides and proteins. Each PCAT contains two peptidase domains that cleave off the secretion signal, two transmembrane domains forming a translocation pathway, and two nucleotide-binding domains that hydrolyze ATP. Previously the crystal structures of a PCAT fromClostridium thermocellum (PCAT1) were determined in the absence and presence of ATP, revealing how ATP binding regulates the protease activity and access to the translocation pathway. However, how the substrate...
Source: eLife - January 14, 2020 Category: Biomedical Science Tags: Structural Biology and Molecular Biophysics Source Type: research

TTBK2 and primary cilia are essential for the connectivity and survival of cerebellar Purkinje neurons
Primary cilia are vital signaling organelles that extend from most types of cells, including neurons and glia. These structures are essential for the development of many tissues and organs, however, their function in adult tissues, particularly neurons in the brain, remains largely unknown. Tau tubulin kinase 2 (TTBK2) is a critical regulator of ciliogenesis, and is also mutated in a hereditary neurodegenerative disorder, spinocerebellar ataxia type 11 (SCA11). Here, we show that conditional knockout ofTtbk2 in adult mice results in degenerative cerebellar phenotypes that recapitulate aspects of SCA11 including motor coord...
Source: eLife - January 14, 2020 Category: Biomedical Science Tags: Cell Biology Neuroscience Source Type: research

< i > Midkine < /i > is a dual regulator of wound epidermis development and inflammation during the initiation of limb regeneration
Formation of a specialized wound epidermis is required to initiate salamander limb regeneration. Yet little is known about the roles of the early wound epidermis during the initiation of regeneration and the mechanisms governing its development into the apical epithelial cap (AEC), a signaling structure necessary for outgrowth and patterning of the regenerate. Here, we elucidate the functions of the early wound epidermis, and further revealmidkine (mk) as a dual regulator of both AEC development and inflammation during the initiation of axolotl limb regeneration. Through loss- and gain-of-function experiments, we demonstra...
Source: eLife - January 14, 2020 Category: Biomedical Science Tags: Developmental Biology Stem Cells and Regenerative Medicine Source Type: research

Degradation of engulfed mitochondria is rate-limiting in Optineurin-mediated mitophagy in neurons
Mitophagy, the selective removal of damaged mitochondria, is thought to be critical to maintain neuronal homeostasis. Mutations of proteins in the pathway cause neurodegenerative diseases, suggesting defective mitochondrial turnover contributes to neurodegeneration. In primary rat hippocampal neurons, we developed a mitophagy induction paradigm where mild oxidative stress induced low levels of mitochondrial damage. Mitophagy-associated proteins were sequentially recruited to depolarized mitochondria followed by sequestration into autophagosomes. The localization of these mitophagy events had a robust somal bias. In basal a...
Source: eLife - January 14, 2020 Category: Biomedical Science Tags: Cell Biology Neuroscience Source Type: research

In vitro reconstitution of branching microtubule nucleation
Eukaryotic cell division requires the mitotic spindle, a microtubule (MT)-based structure which accurately aligns and segregates duplicated chromosomes. The dynamics of spindle formation are determined primarily by correctly localising the MT nucleator, γ-TubulinRingComplex ( γ-TuRC), within the cell. A conserved MT-associated protein complex, Augmin, recruits γ-TuRC to pre-existing spindle MTs, amplifying their number, in an essential cellular phenomenon termed ‘branching’ MT nucleation. Here, we purify endogenous, GFP-tagged Augmin and γ-TuRC fromDrosophila embryos to near homogeneity ...
Source: eLife - January 14, 2020 Category: Biomedical Science Tags: Cell Biology Source Type: research

Biochemical reconstitution of branching microtubule nucleation
Microtubules are nucleated from specific locations at precise times in the cell cycle. However, the factors that constitute these microtubule nucleation pathways and their mode of action still need to be identified. Using purifiedXenopus laevis proteins we biochemically reconstitute branching microtubule nucleation, which is critical for chromosome segregation. We found that besides the microtubule nucleator gamma-tubulin ring complex ( γ-TuRC), the branching effectors augmin and TPX2 are required to efficiently nucleate microtubules from pre-existing microtubules. TPX2 has the unexpected capacity to directly recruit...
Source: eLife - January 14, 2020 Category: Biomedical Science Tags: Biochemistry and Chemical Biology Cell Biology Source Type: research

Imp/IGF2BP levels modulate individual neural stem cell growth and division through < i > myc < /i > mRNA stability
The numerous neurons and glia that form the brain originate from tightly controlled growth and division of neural stem cells, regulated systemically by important known stem cell-extrinsic signals. However, the cell-intrinsic mechanisms that control the distinctive proliferation rates of individual neural stem cells are unknown. Here, we show that the size and division rates ofDrosophilaneural stem cells (neuroblasts) are controlled by the highly conserved RNA binding protein Imp (IGF2BP), via one of its top binding targets in the brain,mycmRNA. We show that Imp stabilisesmycmRNA leading to increased Myc protein levels, lar...
Source: eLife - January 14, 2020 Category: Biomedical Science Tags: Developmental Biology Neuroscience Source Type: research

Stepping down
As Eve Marder stands down as a Deputy Editor ofeLife, she reflects on the need for journals to change and respond to their environment (Source: eLife)
Source: eLife - January 14, 2020 Category: Biomedical Science Source Type: research

Disease-modifying effects of natural Δ9-tetrahydrocannabinol in endometriosis-associated pain
Endometriosis is a chronic painful disease highly prevalent in women that is defined by growth of endometrial tissue outside the uterine cavity and lacks adequate treatment. Medical use of cannabis derivatives is a current hot topic and it is unknown whether phytocannabinoids may modify endometriosis symptoms and development. Here we evaluate the effects of repeated exposure to Δ9-tetrahydrocannabinol (THC) in a mouse model of surgically-induced endometriosis. In this model, female mice develop mechanical hypersensitivity in the caudal abdomen, mild anxiety-like behavior and substantial memory deficits associated wit...
Source: eLife - January 14, 2020 Category: Biomedical Science Tags: Human Biology and Medicine Neuroscience Source Type: research

Nanopore direct RNA sequencing maps the complexity of Arabidopsis mRNA processing and m < sup > 6 < /sup > A modification
Understanding genome organization and gene regulation requires insight into RNA transcription, processing and modification. We adapted nanopore direct RNA sequencing to examine RNA from a wild-type accession of the model plantArabidopsis thaliana and a mutant defective in mRNA methylation (m6A). Here we show that m6A can be mapped in full-length mRNAs transcriptome-wide and reveal the combinatorial diversity of cap-associated transcription start sites, splicing events, poly(A) site choice and poly(A) tail length. Loss of m6A from 3 ’ untranslated regions is associated with decreased relative transcript abundance and ...
Source: eLife - January 14, 2020 Category: Biomedical Science Tags: Chromosomes and Gene Expression Computational and Systems Biology Source Type: research

TRF1 averts chromatin remodelling, recombination and replication dependent-Break Induced Replication at mouse telomeres
Telomeres are a significant challenge to DNA replication and are prone to replication stress and telomere fragility. The shelterin component TRF1 facilitates telomere replication but the molecular mechanism remains uncertain. By interrogating the proteomic composition of telomeres, we show that mouse telomeres lacking TRF1 undergo protein composition reorganisation associated with the recruitment of DNA damage response and chromatin remodellers. Surprisingly, mTRF1 suppresses the accumulation of promyelocytic leukemia (PML) protein, BRCA1 and the SMC5/6 complex at telomeres, which is associated with increased Homologous Re...
Source: eLife - January 14, 2020 Category: Biomedical Science Tags: Cell Biology Chromosomes and Gene Expression Source Type: research

Flower-like patterns in multi-species bacterial colonies
Diverse interactions among species within bacterial colonies lead to intricate spatiotemporal dynamics, which can affect their growth and survival. Here, we describe the emergence of complex structures in a colony grown from mixtures of motile and non-motile bacterial species on a soft agar surface. Time-lapse imaging shows that non-motile bacteria 'hitchhike' on the motile bacteria as the latter migrate outward. The non-motile bacteria accumulate at the boundary of the colony and trigger an instability that leaves behind striking flower-like patterns. The mechanism of the front instability governing this pattern formation...
Source: eLife - January 14, 2020 Category: Biomedical Science Tags: Physics of Living Systems Source Type: research

Duodenum Intestine-Chip for preclinical drug assessment in a human relevant model
Induction of intestinal drug metabolizing enzymes can complicate the development of new drugs, owing to the potential to cause drug-drug interactions (DDIs) leading to changes in pharmacokinetics, safety and efficacy. The development of a human-relevant model of the adult intestine that accurately predicts CYP450 induction could help address this challenge as species differences preclude extrapolation from animals. Here, we combined organoids and Organs-on-Chips technology to create a human Duodenum Intestine-Chip that emulates intestinal tissue architecture and functions, that are relevant for the study of drug transport,...
Source: eLife - January 14, 2020 Category: Biomedical Science Tags: Cell Biology Source Type: research

NINscope, a versatile miniscope for multi-region circuit investigations
Miniaturized fluorescence microscopes (miniscopes) have been instrumental to monitor neural signals during unrestrained behavior and their open-source versions have made them affordable. Often, the footprint and weight of open-source miniscopes is sacrificed for added functionality. Here, we present NINscope: a light-weight miniscope with a small footprint that integrates a high-sensitivity image sensor, an inertial measurement unit and an LED driver for an external optogenetic probe. We use it to perform the first concurrent cellular resolution recordings from cerebellum and cerebral cortex in unrestrained mice, demonstra...
Source: eLife - January 14, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

< i > MYC < /i > and < i > Twist1 < /i > cooperate to drive metastasis by eliciting crosstalk between cancer and innate immunity
Metastasis is a major cause of cancer mortality. We generated an autochthonous transgenic mouse model whereby conditional expression ofMYC andTwist1 enables hepatocellular carcinoma (HCC) to metastasize in>90% of mice.MYC andTwist1 cooperate and their sustained expression is required to elicit a transcriptional program associated with the activation of innate immunity, through secretion of a cytokinome that elicits recruitment and polarization of tumor associated macrophages (TAMs). Systemic treatment with Ccl2 and Il13 inducedMYC-HCCs to metastasize; whereas, blockade of Ccl2 and Il13 abrogatedMYC/Twist1-HCC metastasis...
Source: eLife - January 14, 2020 Category: Biomedical Science Tags: Cancer Biology Source Type: research

Cytomegalovirus protein m154 perturbs the adaptor protein-1 compartment mediating broad-spectrum immune evasion
Cytomegaloviruses (CMVs) are ubiquitous pathogens known to employ numerous immunoevasive strategies that significantly impair the ability of the immune system to eliminate the infected cells. Here, we report that the single mouse CMV (MCMV) protein, m154, downregulates multiple surface molecules involved in the activation and costimulation of the immune cells. We demonstrate that m154 uses its cytoplasmic tail motif, DD, to interfere with the adaptor protein-1 (AP-1) complex, implicated in intracellular protein sorting and packaging. As a consequence of the perturbed AP-1 sorting, m154 promotes lysosomal degradation of sev...
Source: eLife - January 13, 2020 Category: Biomedical Science Tags: Immunology and Inflammation Microbiology and Infectious Disease Source Type: research

The structure of species discrimination signals across a primate radiation
Discriminating conspecifics from heterospecifics can help avoid costly interactions between closely related sympatric species. The guenons, a recent primate radiation, exhibit high degrees of sympatry and form multi-species groups. Guenons have species-specific colorful face patterns hypothesized to function in species discrimination. Here, we use a machine learning approach to identify face regions most essential for species classification across fifteen guenon species. We validate these computational results using experiments with live guenons, showing that facial traits critical for accurate classification influence sel...
Source: eLife - January 13, 2020 Category: Biomedical Science Tags: Evolutionary Biology Source Type: research

Structural basis for COMPASS recognition of an H2B-ubiquitinated nucleosome
We report here the cryo-EM structure of a six-protein core COMPASS subcomplex, which can methylate H3K4 and be stimulated by H2B-Ub, bound to a ubiquitinated nucleosome. Our structure shows that COMPASS spans the face of the nucleosome, recognizing ubiquitin on one face of the nucleosome and methylating H3 on the opposing face. As compared to the structure of the isolated core complex, Set1 undergoes multiple structural rearrangements to cement interactions with the nucleosome and with ubiquitin. The critical Set1 RxxxRR motif adopts a helix that mediates bridging contacts between the nucleosome, ubiquitin and COMPASS. The...
Source: eLife - January 10, 2020 Category: Biomedical Science Tags: Chromosomes and Gene Expression Structural Biology and Molecular Biophysics Source Type: research

Two forms of Opa1 cooperate to complete fusion of the mitochondrial inner-membrane
Mitochondrial membrane dynamics is a cellular rheostat that relates metabolic function and organelle morphology. Using anin vitro reconstitution system, we describe a mechanism for how mitochondrial inner-membrane fusion is regulated by the ratio of two forms of Opa1. We found that the long-form of Opa1 (l-Opa1) is sufficient for membrane docking, hemifusion and low levels of content release. However, stoichiometric levels of the processed, short form of Opa1 (s-Opa1) work together with l-Opa1 to mediate efficient and fast membrane pore opening. Additionally, we found that excess levels of s-Opa1 inhibit fusion activity, a...
Source: eLife - January 10, 2020 Category: Biomedical Science Tags: Structural Biology and Molecular Biophysics Source Type: research

Metabolic signature in nucleus accumbens for anti-depressant-like effects of acetyl-L-carnitine
Emerging evidence suggests that hierarchical status provide vulnerability to develop stress-induced depression. Energy metabolic changes in the nucleus accumbens (NAc) were recently related to hierarchical status and vulnerability to develop depression-like behavior. Acetyl-L-carnitine (LAC), a mitochondria-boosting supplement, has shown promising antidepressant-like effects opening therapeutic opportunities for restoring energy balance in depressed patients. We investigated the metabolic impact in the NAc of antidepressant LAC treatment in chronically-stressed mice using1H-magnetic resonance spectroscopy (1H-MRS). High ra...
Source: eLife - January 10, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

Point of View: Open Exploration
Arguments in support of open science tend to focus on confirmatory research practices. Here we argue that exploratory research should also be encouraged within the framework of open science. We lay out the benefits of 'open exploration' and propose two complementary ways to implement this with little infrastructural change. (Source: eLife)
Source: eLife - January 9, 2020 Category: Biomedical Science Source Type: research

Coordination of humoral immune factors dictates compatibility between < i > Schistosoma mansoni < /i > and < i > Biomphalaria glabrata < /i >
Immune factors in snails of the genusBiomphalaria are critical for combatingSchistosoma mansoni, the predominant cause of human intestinal schistosomiasis. Independently, many of these factors play an important role in, but do not fully define, the compatibility between the model snailB. glabrata, andS. mansoni. Here, we demonstrate association between four previously characterized humoral immune molecules;BgFREP3,BgTEP1,BgFREP2 and Biomphalysin. We also identify unique immune determinants in the plasma ofS. mansoni-resistantB. glabrata that associate with the incompatible phenotype. These factors coordinate to initiate ha...
Source: eLife - January 9, 2020 Category: Biomedical Science Tags: Microbiology and Infectious Disease Source Type: research

Robust perisomatic GABAergic self-innervation inhibits basket cells in the human and mouse supragranular neocortex
Inhibitory autapses are self-innervating synaptic connections in GABAergic interneurons in the brain. Autapses in neocortical layers have not been systematically investigated, and their function in different mammalian species and specific interneuron types is poorly known. We investigated GABAergic parvalbumin-expressing basket cells (pvBCs) in layer 2/3 (L2/3) in human neocortical tissue resected in deep-brain surgery, and in mice as control. Most pvBCs showed robust GABAAR-mediated self-innervation in both species, but autapses were rare in nonfast-spiking GABAergic interneurons. Light- and electron microscopy analyses r...
Source: eLife - January 9, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

Distinct cytoskeletal proteins define zones of enhanced cell wall synthesis in < i > Helicobacter pylori < /i >
Helical cell shape is necessary for efficient stomach colonization byHelicobacter pylori, but the molecular mechanisms for generating helical shape remain unclear. The helical centerline pitch and radius of wild-typeH. pylori cells dictate surface curvatures of considerably higher positive and negative Gaussian curvatures than those present in straight- or curved-rodH. pylori. Quantitative 3D microscopy analysis of short pulses with eitherN-acetylmuramic acid or D-alanine metabolic probes showed that cell wall growth is enhanced at both sidewall curvature extremes. Immunofluorescence revealed MreB is most abundant at negat...
Source: eLife - January 9, 2020 Category: Biomedical Science Tags: Microbiology and Infectious Disease Source Type: research

Origin and role of the cerebrospinal fluid bidirectional flow in the central canal
Circulation of the cerebrospinal fluid (CSF) contributes to body axis formation and brain development. Here, we investigated the unexplained origins of the CSF flow bidirectionality in the central canal of the spinal cord of 30 hpf zebrafish embryos and its impact on development. Experiments combined with modeling and simulations demonstrate that the CSF flow is generated locally by caudally-polarized motile cilia along the ventral wall of the central canal. The closed geometry of the canal imposes the average flow rate to be null, explaining the reported bidirectionality. We also demonstrate that at this early stage, moti...
Source: eLife - January 9, 2020 Category: Biomedical Science Tags: Physics of Living Systems Source Type: research

A processive rotary mechanism couples substrate unfolding and proteolysis in the ClpXP degradation machinery
The ClpXP degradation machine consists of a hexameric AAA+ unfoldase (ClpX) and a pair of heptameric serine protease rings (ClpP) that unfold, translocate, and subsequently degrade client proteins. ClpXP is an important target for drug development against infectious diseases. Although structures are available for isolated ClpX and ClpP rings, it remains unknown how symmetry mismatched ClpX and ClpP work in tandem for processive substrate translocation into the ClpP proteolytic chamber. Here we present cryo-EM structures of the substrate-bound ClpXP complex fromNeisseria meningitidisat 2.3 to 3.3 Å resolution. The str...
Source: eLife - January 9, 2020 Category: Biomedical Science Tags: Structural Biology and Molecular Biophysics Source Type: research

Cardiac ryanodine receptor distribution is dynamic and changed by auxiliary proteins and post-translational modification
The effects of the immunophilins, FKBP12 and FKBP12.6, and phosphorylation on type II ryanodine receptor (RyR2) arrangement and function were examined using correlation microscopy (line scan confocal imaging of Ca2+sparks and dual-tilt electron tomography) and dSTORM imaging of permeabilized Wistar rat ventricular myocytes. Saturating concentrations (10 µmol/L) of either FKBP12 or 12.6 significantly reduced the frequency, spread, amplitude and Ca2+ spark mass relative to control, while the tomograms revealed both proteins shifted the tetramers into a largely side-by-side configuration. Phosphorylation of immunophilin...
Source: eLife - January 9, 2020 Category: Biomedical Science Tags: Cell Biology Source Type: research

Cell type specific control of basolateral amygdala neuronal circuits via entorhinal cortex-driven feedforward inhibition
The basolateral amygdala (BLA) plays a vital role in associating sensory stimuli with salient valence information. Excitatory principal neurons (PNs) undergo plastic changes to encode this association; however, local BLA inhibitory interneurons (INs) gate PN plasticity via feedforward inhibition (FFI). Despite literature implicating parvalbumin expressing (PV+) INs in FFI in cortex and hippocampus, prior anatomical experiments in BLA implicate somatostatin expressing (Sst+) INs. The lateral entorhinal cortex (LEC) projects to BLA where it drives FFI. In the present study, we explored the role of interneurons in this circui...
Source: eLife - January 9, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

Defining murine monocyte differentiation into colonic and ileal macrophages
Monocytes are circulating short-lived macrophage precursors that are recruited on demand from the blood to sites of inflammation and challenge. In steady state, classical monocytes give rise to vasculature-resident cells that patrol the luminal side of the endothelium. In addition, classical monocytes feed macrophage compartments of selected organs, including barrier tissues, such as the skin and intestine, as well as the heart. Monocyte differentiation under conditions of inflammation has been studied in considerable detail. In contrast, monocyte differentiation under non-inflammatory conditions remains less well understo...
Source: eLife - January 8, 2020 Category: Biomedical Science Tags: Immunology and Inflammation Source Type: research

YAP regulates cell size and growth dynamics via non-cell autonomous mediators
The Hippo pathway regulates organ size, regeneration, and cell growth by controlling the stability of the transcription factor, YAP (Yorkie in Drosophila). When there is tissue damage, YAP is activated allowing the restoration of homeostatic tissue size. The exact signals by which YAP is activated are still not fully understood, but its activation is known to affect both cell size and cell number. Here we used cultured cells to examine the coordinated regulation of cell size and number under the control of YAP. Our experiments in isogenic HEK293 cells reveal that YAP can affect cell size and number by independent circuits....
Source: eLife - January 8, 2020 Category: Biomedical Science Tags: Cell Biology Source Type: research

A genome-wide view of the de-differentiation of central nervous system endothelial cells in culture
In this report, we compare transcriptional and accessible chromatin landscapes of acutely isolated mouse CNS ECs versus mouse CNS ECs in short-term in vitro culture. We observe that standard culture conditions are associated with a rapid and selective loss of BBB transcripts and chromatin features, as well as a greatly reduced level of beta-catenin signaling. Interestingly, forced expression of a stabilized derivative of beta-catenin, which in vivo leads to a partial conversion of non-BBB CNS ECs to a BBB-like state, has little or no effect on gene expression or chromatin accessibility in vitro. (Source: eLife)
Source: eLife - January 8, 2020 Category: Biomedical Science Tags: Genetics and Genomics Neuroscience Source Type: research

Comprehensive transcriptome analysis of cochlear spiral ganglion neurons at multiple ages
Inner ear cochlear spiral ganglion neurons (SGNs) transmit auditory information to the brainstem. Recent single cell RNA-Seq studies have revealed heterogeneities within SGNs. Nonetheless, much remains unknown about the transcriptome of SGNs, especially which genes are specifically expressed in SGNs. To address these questions we needed a deeper and broader gene coverage than that in previous studies. We performed bulk RNA-Seq on mouse SGNs at five ages, and on two reference cell types (hair cells and glia). Their transcriptome comparison identified genes previously unknown to be specifically expressed in SGNs. To validate...
Source: eLife - January 8, 2020 Category: Biomedical Science Tags: Developmental Biology Neuroscience Source Type: research

How nitric oxide helps update memories
Some dopaminergic neurons release both dopamine and nitric oxide to increase the flexibility of olfactory memories. (Source: eLife)
Source: eLife - January 8, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

Two roles for the yeast transcription coactivator SAGA and a set of genes redundantly regulated by TFIID and SAGA
Deletions within genes coding for subunits of the transcription coactivator SAGA caused strong genome-wide defects in transcription and SAGA-mediated chromatin modifications. In contrast, rapid SAGA depletion produced only modest transcription defects at 13% of protein-coding genes – genes that are generally more sensitive to rapid TFIID depletion. However, transcription of these 'coactivator-redundant' genes is strongly affected by rapid depletion of both factors, showing the overlapping functions of TFIID and SAGA at this gene set. We suggest that this overlapping function is linked to TBP-DNA recruitment. The rema...
Source: eLife - January 8, 2020 Category: Biomedical Science Tags: Chromosomes and Gene Expression Source Type: research

Purinergic signaling in cochlear supporting cells reduces hair cell excitability by increasing the extracellular space
Neurons in developing sensory pathways exhibit spontaneous bursts of electrical activity that are critical for survival, maturation and circuit refinement. In the auditory system, intrinsically generated activity arises within the cochlea, but the molecular mechanisms that initiate this activity remain poorly understood. We show that burst firing of mouse inner hair cells prior to hearing onset requires P2RY1 autoreceptors expressed by inner supporting cells. P2RY1 activation triggers K+ efflux and depolarization of hair cells, as well as osmotic shrinkage of supporting cells that dramatically increased the extracellular s...
Source: eLife - January 8, 2020 Category: Biomedical Science Tags: Developmental Biology Neuroscience Source Type: research

Casposase structure and the mechanistic link between DNA transposition and spacer acquisition by CRISPR-Cas
Key to CRISPR-Cas adaptive immunity is maintaining an ongoing record of invading nucleic acids, a process carried out by the Cas1-Cas2 complex that integrates short segments of foreign genetic material (spacers) into the CRISPR locus. It is hypothesized that Cas1 evolved from casposases, a novel class of transposases. We show here that theMethanosarcina mazei casposase can integrate varied forms of the casposon end in vitro, and recapitulates several properties of CRISPR-Cas integrases including site-specificity. The X-ray structure of the casposase bound to DNA representing the product of integration reveals a tetramer wi...
Source: eLife - January 8, 2020 Category: Biomedical Science Tags: Structural Biology and Molecular Biophysics Source Type: research

What about faculty?
After two heart attacks in three years, an associate professor discusses the challenges of faculty life. (Source: eLife)
Source: eLife - January 8, 2020 Category: Biomedical Science Source Type: research

STRIPAK directs PP2A activity toward MAP4K4 to promote oncogenic transformation of human cells
Alterations involving serine-threonine phosphatase PP2A subunits occur in a range of human cancers and partial loss of PP2A function contributes to cell transformation. Displacement of regulatory B subunits by the SV40 Small T antigen (ST) or mutation/deletion of PP2A subunits alters the abundance and types of PP2A complexes in cells, leading to transformation. Here we show that ST not only displaces common PP2A B subunits but also promotes A-C subunit interactions with alternative B subunits (B', striatins) that are components of the Striatin-interacting phosphatase and kinase (STRIPAK) complex. We found that STRN4, a mem...
Source: eLife - January 8, 2020 Category: Biomedical Science Tags: Cancer Biology Source Type: research

Presynaptic developmental plasticity allows robust sparse wiring of the < i > Drosophila < /i > mushroom body
In order to represent complex stimuli, principle neurons of associative learning regions receive combinatorial sensory inputs. Density of combinatorial innervation is theorized to determine the number of distinct stimuli that can be represented and distinguished from one another, with sparse innervation thought to optimize the complexity of representations in networks of limited size. How the convergence of combinatorial inputs to principle neurons of associative brain regions is established during development is unknown. Here, we explore the developmental patterning of sparse olfactory inputs to Kenyon cells of theDrosoph...
Source: eLife - January 8, 2020 Category: Biomedical Science Tags: Developmental Biology Neuroscience Source Type: research

Resolving multisensory and attentional influences across cortical depth in sensory cortices
In our environment our senses are bombarded with a myriad of signals, only a subset of which is relevant for our goals. Using sub-millimeter-resolution fMRI at 7T we resolved BOLD-response and activation patterns across cortical depth in early sensory cortices to auditory, visual and audiovisual stimuli under auditory or visual attention. In visual cortices, auditory stimulation induced widespread inhibition irrespective of attention, whereas auditory relative to visual attention suppressed mainly central visual field representations. In auditory cortices, visual stimulation suppressed activations, but amplified responses ...
Source: eLife - January 8, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

Cell-type specific regulation of neuronal intrinsic excitability by macroautophagy
The basal ganglia are a group of subcortical nuclei that contribute to action selection and reinforcement learning. The principal neurons of the striatum, spiny projection neurons of the direct (dSPN) and indirect (iSPN) pathways, maintain low intrinsic excitability, requiring convergent excitatory inputs to fire. Here, we examined the role of autophagy in mouse SPN physiology and animal behavior by generating conditional knockouts of Atg7 in either dSPNs or iSPNs. Loss of autophagy in either SPN population led to changes in motor learning but distinct effects on cellular physiology. dSPNs, but not iSPNs, required autophag...
Source: eLife - January 8, 2020 Category: Biomedical Science Tags: Cell Biology Neuroscience Source Type: research

Vangl2 acts at the interface between actin and N-cadherin to modulate mammalian neuronal outgrowth
Dynamic mechanical interactions between adhesion complexes and the cytoskeleton are essential for axon outgrowth and guidance. Whether planar cell polarity (PCP) proteins, which regulate cytoskeleton dynamics and appear necessary for some axon guidance, also mediate interactions with membrane adhesion is still unclear. Here we show that Vangl2 controls growth cone velocity by regulating the internal retrograde actin flow in an N-cadherin-dependent fashion. Single molecule tracking experiments show that the loss ofVangl2 decreased fast-diffusing N-cadherin membrane molecules and increased confined N-cadherin trajectories. U...
Source: eLife - January 7, 2020 Category: Biomedical Science Tags: Cell Biology Developmental Biology Source Type: research

Nucleotide inhibition of the pancreatic ATP-sensitive K < sup > + < /sup > channel explored with patch-clamp fluorometry
Pancreatic ATP-sensitive K+ channels (KATP) comprise four inward rectifier subunits (Kir6.2), each associated with a sulphonylurea receptor (SUR1). ATP/ADP binding to Kir6.2 shuts KATP. Mg-nucleotide binding to SUR1 stimulates KATP. In the absence of Mg2+, SUR1 increases the apparent affinity for nucleotide inhibition at Kir6.2 by an unknown mechanism. We simultaneously measured channel currents and nucleotide binding to Kir6.2. Fits to combined data sets suggest that KATP closes with only one nucleotide molecule bound. A Kir6.2 mutation (C166S) that increases channel activity did not affect nucleotide binding, but greatly...
Source: eLife - January 7, 2020 Category: Biomedical Science Tags: Structural Biology and Molecular Biophysics Source Type: research

Compartmentalized < i > oskar < /i > degradation in the germ plasm safeguards germline development
Partitioning of mRNAs into ribonucleoprotein (RNP) granules supports diverse regulatory programs within the crowded cytoplasm. At least two types of RNP granules populate the germ plasm, a cytoplasmic domain at the posterior of theDrosophila oocyte and embryo. Germ granules deliver mRNAs required for germline development to pole cells, the germ cell progenitors. A second type of RNP granule, here named founder granules, containsoskar mRNA, which encodes the germ plasm organizer. Whereasoskar mRNA is essential for germ plasm assembly during oogenesis, we show that it is toxic to pole cells. Founder granules mediate compartm...
Source: eLife - January 7, 2020 Category: Biomedical Science Tags: Developmental Biology Source Type: research

The genetic basis of aneuploidy tolerance in wild yeast
Aneuploidy is highly detrimental during development yet common in cancers and pathogenic fungi – what gives rise to differences in aneuploidy tolerance remains unclear. We previously showed that wild isolates ofSaccharomyces cerevisiae tolerate chromosome amplification while laboratory strains used as a model for aneuploid syndromes do not. Here, we mapped the genetic basis to Ssd1, an RNA-binding translational regulator that is functional in wild aneuploids but defective in laboratory strain W303. Loss ofSSD1 recapitulates myriad aneuploidy signatures previously taken as eukaryotic responses. We show that aneuploidy...
Source: eLife - January 7, 2020 Category: Biomedical Science Tags: Chromosomes and Gene Expression Source Type: research

The challenges of maintaining genetic privacy
Two studies suggest that a determined adversary may be able to obtain genetic information without permission from some genealogy databases. (Source: eLife)
Source: eLife - January 7, 2020 Category: Biomedical Science Tags: Evolutionary Biology Genetics and Genomics Source Type: research

Counting the Minutes
A newly discovered mechanism that causes the 'Minute' phenotype in fruit flies can explain how organisms are able to eliminate the mutant cells that arise occasionally during development. (Source: eLife)
Source: eLife - January 7, 2020 Category: Biomedical Science Tags: Developmental Biology Source Type: research

The GTPase Nog1 co-ordinates assembly, maturation and quality control of distant ribosomal functional centers
Eukaryotic ribosome precursors acquire translation competence in the cytoplasm through stepwise release of bound assembly factors, and proofreading of their functional centers. In case of the pre-60S, these steps include removal of placeholders Rlp24, Arx1 and Mrt4 that prevent premature loading of the ribosomal protein eL24, the protein-folding machinery at the polypeptide exit tunnel (PET), and the ribosomal stalk, respectively. Here, we reveal that sequential ATPase and GTPase activities license release factors Rei1 and Yvh1 to trigger Arx1 and Mrt4 removal. Drg1-ATPase activity removes Rlp24 from the GTPase Nog1 on the...
Source: eLife - January 7, 2020 Category: Biomedical Science Tags: Biochemistry and Chemical Biology Source Type: research

Decreasing human body temperature in the United States since the industrial revolution
In the US, the normal, oral temperature of adults is, on average, lower than the canonical 37 °C established in the 19th century. We postulated that body temperature has decreased over time. Using measurements from three cohorts--the Union Army Veterans of the Civil War (N = 23,710; measurement years 1860 –1940), the National Health and Nutrition Examination Survey I (N = 15,301; 1971–1975), and the Stanford Translational Research Integrated Database Environment (N = 150,280; 2007–2017)--we determined that mean body temperature in men and women, after adjusting for age, height, weight and, in s ome mo...
Source: eLife - January 7, 2020 Category: Biomedical Science Tags: Human Biology and Medicine Source Type: research

Roles of C/EBP class bZip proteins in the growth and cell competition of < i > Rp < /i > ( ‘Minute’) mutants in < i > Drosophila < /i >
Reduced copy number of ribosomal protein (Rp) genes adversely affects both flies and mammals.Xrp1 encodes a reportedlyDrosophila-specific AT-hook, bZIP protein responsible for many of the effects including the elimination ofRp mutant cells by competition with wild type cells. Irbp18, an evolutionarily conserved bZIP gene, heterodimerizes with Xrp1 and with another bZip protein, dATF4. We show that Irbp18 is required for the effects of Xrp1, whereas dATF4 does not share the same phenotype, indicating that Xrp1/Irbp18 is the complex active inRp mutant cells, independently of other complexes that share Irbp18. Xrp1 and Irbp18...
Source: eLife - January 7, 2020 Category: Biomedical Science Tags: Developmental Biology Source Type: research