TY - JOUR AB - Orientation in space is represented in specialized brain circuits. Persistent head direction signals are transmitted from anterior thalamus to the presubiculum, but the identity of the presubicular target neurons, their connectivity and function in local microcircuits are unknown. Here, we examine how thalamic afferents recruit presubicular principal neurons and Martinotti interneurons, and the ensuing synaptic interactions between these cells. Pyramidal neuron activation of Martinotti cells in superficial layers is strongly facilitating such that high-frequency head directional stimulation efficiently unmutes synaptic excitation. Martinotti-cell feedback plays a dual role: precisely timed spikes may not inhibit the firing of in-tune head direction cells, while exerting lateral inhibition. Autonomous attractor dynamics emerge from a modelled network implementing wiring motifs and timing sensitive synaptic interactions in the pyramidal - Martinotti-cell feedback loop. This inhibitory microcircuit is therefore tuned to refine and maintain head direction information in the presubiculum. AU - Simonnet, Jean AU - Nassar, Mérie AU - Stella, Federico AU - Cohen, Ivan AU - Mathon, Bertrand AU - Boccara, Charlotte AU - Miles, Richard AU - Fricker, Desdemona ID - 514 JF - Nature Communications SN - 20411723 TI - Activity dependent feedback inhibition may maintain head direction signals in mouse presubiculum VL - 8 ER - TY - JOUR AB - The oxidative phosphorylation electron transport chain (OXPHOS-ETC) of the inner mitochondrial membrane is composed of five large protein complexes, named CI-CV. These complexes convert energy from the food we eat into ATP, a small molecule used to power a multitude of essential reactions throughout the cell. OXPHOS-ETC complexes are organized into supercomplexes (SCs) of defined stoichiometry: CI forms a supercomplex with CIII2 and CIV (SC I+III2+IV, known as the respirasome), as well as with CIII2 alone (SC I+III2). CIII2 forms a supercomplex with CIV (SC III2+IV) and CV forms dimers (CV2). Recent cryo-EM studies have revealed the structures of SC I+III2+IV and SC I+III2. Furthermore, recent work has shed light on the assembly and function of the SCs. Here we review and compare these recent studies and discuss how they have advanced our understanding of mitochondrial electron transport. AU - Letts, James A AU - Sazanov, Leonid A ID - 515 IS - 10 JF - Nature Structural and Molecular Biology SN - 15459993 TI - Clarifying the supercomplex: The higher-order organization of the mitochondrial electron transport chain VL - 24 ER - TY - JOUR AB - We present an experimental setup that creates a shear flow with zero mean advection velocity achieved by counterbalancing the nonzero streamwise pressure gradient by moving boundaries, which generates plane Couette-Poiseuille flow. We obtain experimental results in the transitional regime for this flow. Using flow visualization, we characterize the subcritical transition to turbulence in Couette-Poiseuille flow and show the existence of turbulent spots generated by a permanent perturbation. Due to the zero mean advection velocity of the base profile, these turbulent structures are nearly stationary. We distinguish two regions of the turbulent spot: the active turbulent core, which is characterized by waviness of the streaks similar to traveling waves, and the surrounding region, which includes in addition the weak undisturbed streaks and oblique waves at the laminar-turbulent interface. We also study the dependence of the size of these two regions on Reynolds number. Finally, we show that the traveling waves move in the downstream (Poiseuille) direction. AU - Klotz, Lukasz AU - Lemoult, Grégoire M AU - Frontczak, Idalia AU - Tuckerman, Laurette AU - Wesfreid, José ID - 513 IS - 4 JF - Physical Review Fluids TI - Couette-Poiseuille flow experiment with zero mean advection velocity: Subcritical transition to turbulence VL - 2 ER - TY - JOUR AB - Cyanobacteria are mostly engineered to be sustainable cell-factories by genetic manipulations alone. Here, by modulating the concentration of allosteric effectors, we focus on increasing product formation without further burdening the cells with increased expression of enzymes. Resorting to a novel 96-well microplate cultivation system for cyanobacteria, and using lactate-producing strains of Synechocystis PCC6803 expressing different l-lactate dehydrogenases (LDH), we titrated the effect of 2,5-anhydro-mannitol supplementation. The latter acts in cells as a nonmetabolizable analogue of fructose 1,6-bisphosphate, a known allosteric regulator of one of the tested LDHs. In this strain (SAA023), we achieved over 2-fold increase of lactate productivity. Furthermore, we observed that as carbon is increasingly deviated during growth toward product formation, there is an increased fixation rate in the population of spontaneous mutants harboring an impaired production pathway. This is a challenge in the development of green cell factories, which may be countered by the incorporation in biotechnological processes of strategies such as the one pioneered here. AU - Du, Wei AU - Angermayr, Andreas AU - Jongbloets, Joeri AU - Molenaar, Douwe AU - Bachmann, Herwig AU - Hellingwerf, Klaas AU - Branco Dos Santos, Filipe ID - 520 IS - 3 JF - ACS Synthetic Biology SN - 21615063 TI - Nonhierarchical flux regulation exposes the fitness burden associated with lactate production in Synechocystis sp. PCC6803 VL - 6 ER - TY - JOUR AB - Let X and Y be proper metric spaces. We show that a coarsely n-to-1 map f:X→Y induces an n-to-1 map of Higson coronas. This viewpoint turns out to be successful in showing that the classical dimension raising theorems hold in large scale; that is, if f:X→Y is a coarsely n-to-1 map between proper metric spaces X and Y then asdim(Y)≤asdim(X)+n−1. Furthermore we introduce coarsely open coarsely n-to-1 maps, which include the natural quotient maps via a finite group action, and prove that they preserve the asymptotic dimension. AU - Austin, Kyle AU - Virk, Ziga ID - 521 JF - Topology and its Applications SN - 01668641 TI - Higson compactification and dimension raising VL - 215 ER -