optogenetics

In contrast to their near-disappearance in the adult neocortex, Cajal-Retzius cells have been suggested to persist longer in the hippocampus. A distinctive feature of the mature hippocampus, not maintained by other cortical areas, is its ability to sustain adult neurogenesis. Here, we have investigated whether environmental manipulations affecting hippocampal postnatal neurogenesis have a parallel impact on Cajal-Retzius cells. We used multiple mouse reporter lines to unequivocally identify Cajal-Retzius cells and quantify their densities during postnatal development...

During bone remodelling, osteoclasts induce chemotaxis of osteoblasts and yet maintain spatial segregation. We show that osteoclasts express the repulsive guidance factor Semaphorin 4D and induce contact inhibition of locomotion (CIL) in osteoblasts through its receptor Plexin-B1. To examine causality and elucidate how localized Plexin-B1 stimulation may spatiotemporally coordinate its downstream targets in guiding cell migration, we develop an optogenetic tool for Plexin-B1 designated optoPlexin. Precise optoPlexin activation at the leading edge of migrating osteoblasts readily induces local retraction and, unexpectedly, distal protrusions to steer cells away...

BACKGROUND: Preclinical neuroimaging allows for the assessment of brain anatomy, connectivity and function in laboratory animals, such as mice and rats. Most of these studies are performed under anesthesia to avoid movement during the scanning sessions. METHOD: Due to the limitations associated with anesthetized imaging, recent efforts have been made to conduct rodent imaging studies in awake animals, habituated to the restraint systems used in these instances. As of now, only one such system is commercially available for mouse scanning (Animal Imaging Research, Boston, MA, USA) integrating the radiofrequency coil electronics with the restraining element, an approach which, although effective in reducing head motion during awake imaging, has some limitations...

The ellipsoid body (EB) in the Drosophila brain is a central complex (CX) substructure that harbors circumferentially laminated ring (R) neuron axons and mediates multifaceted sensory integration and motor coordination functions. However, what regulates R axon lamination and how lamination affects R neuron function remain unknown. We show here that the EB is sequentially innervated by small-field and large-field neurons, and that early-developing EB neurons play an important regulatory role in EB laminae formation...

We examined seizure-susceptibility in a Drosophila model of human epilepsy using optogenetic stimulation of ReaChR opsin. Photostimulation of the seizure-sensitive mutant para(bss1) causes behavioral paralysis that resembles paralysis caused by mechanical stimulation, in many aspects. Electrophysiology shows that photostimulation evokes abnormal seizure-like neuronal firing in para(bss1) followed by a quiescent period resembling synaptic failure and apparently responsible for paralysis. The pattern of neuronal activity concludes with seizure-like activity just prior to recovery (recovery)...

Striatal cholinergic interneurons (CIN) are pivotal for the regulation of the striatal network. Acetylcholine (ACh) released by CIN is centrally involved in reward behavior as well as locomotor or cognitive functions. Recently, BAC transgenic mice expressing channelrhodopsin-2 (ChR2) protein under the control of the choline acetyltransferase (ChAT) promoter (ChAT-ChR2) and displaying almost 50 extra copies of the VAChT gene were used to dissect cholinergic circuit connectivity and function using optogenetic approaches...

Optogenetics promises precise spatiotemporal control of neural processes using light. However, the spatial extent of illumination within the brain is difficult to control and cannot be adjusted using standard fiber optics. We demonstrate that optical fibers with tapered tips can be used to illuminate either spatially restricted or large brain volumes. Remotely adjusting the light input angle to the fiber varies the light-emitting portion of the taper over several millimeters without movement of the implant...

Stress-induced hyperglycemia is a fundamental adaptive response that mobilizes energy stores in response to threats. Here, our examination of the contributions of the central catecholaminergic (CA) neuronal system to this adaptive response revealed that CA neurons in the ventrolateral medulla (VLM) control stress-induced hyperglycemia. Ablation of VLM CA neurons abolished the hyperglycemic response to both physical and psychological stress, whereas chemogenetic activation of these neurons was sufficient to induce hyperglycemia...

Sensory processing must be sensitive enough to encode faint signals near the noise floor but selective enough to differentiate between similar stimuli. Here we describe a layer 6 corticothalamic (L6 CT) circuit in the mouse auditory forebrain that alternately biases sound processing toward hypersensitivity and improved behavioral sound detection or dampened excitability and enhanced sound discrimination. Optogenetic activation of L6 CT neurons could increase or decrease the gain and tuning precision in the thalamus and all layers of the cortical column, depending on the timing between L6 CT activation and sensory stimulation...

BACKGROUND: Negative reinforcement theories of drug addiction posit that addicts use drugs to alleviate negative mood states. In a preclinical model developed in our laboratory, rats exhibit negative affect to a normally rewarding taste cue when it predicts impending but delayed cocaine. The emergence of this state is accompanied by a reduction in dopamine concentration in the rostral nucleus accumbens shell. However, the rostral and caudal regions of the shell have been implicated in promoting opposing appetitive and aversive states, respectively...

The Drosophila melanogaster heart has become a principal model in which to study cardiac physiology and development. While the morphology of the heart in Drosophila and mammals is different, many of the molecular mechanisms that underlie heart development and function are similar and function can be assessed by similar physiological measurements, such as cardiac output, rate, and time in systole or diastole. Here, we have utilized an intact, optogenetic approach to assess the neural influence on heart rate in the third instar larvae...

Key mitochondrial functions such as ATP production, Ca(2+) uptake and release, and substrate accumulation depend on the proton electrochemical gradient (ΔμH(+)) across the inner membrane. Although several drugs can modulate ΔμH(+), their effects are hardly reversible, and lack cellular specificity and spatial resolution. Although channelrhodopsins are widely used to modulate the plasma membrane potential of excitable cells, mitochondria have thus far eluded optogenetic control. Here we describe a toolkit of optometabolic constructs based on selective targeting of channelrhodopsins with distinct functional properties to the inner mitochondrial membrane of intact cells...

The conversion of light energy into ion gradients across biological membranes is one of the most fundamental reactions in primary biological energy transduction. Recently, the structure of the first light-activated Na(+) pump, Krokinobacter eikastus rhodopsin 2 (KR2), was resolved at atomic resolution [Kato HE, et al. (2015) Nature 521:48-53]. To elucidate its molecular mechanism for Na(+) pumping, we perform here extensive classical and quantum molecular dynamics (MD) simulations of transient photocycle states...

We genetically encoded three new caged tyrosine analogues with improved photochemical properties by using an engineered pyrrolysyl-tRNA synthetase/tRNACUA pair in bacterial and mammalian cells. We applied the new tyrosine analogues to the photoregulation of firefly luciferase by caging its key tyrosine residue, Tyr340, and observed excellent off-to-on light switching. This reporter was then used to evaluate the activation rates of the different light-removable protecting groups in live cells. We identified the nitropiperonyl caging group as an excellent compromise between incorporation efficiency and photoactivation properties...

Cytoskeletal mechanics regulates cell morphodynamics and many physiological processes. While contractility is known to be largely RhoA-dependent, the process by which localized biochemical signals are translated into cell-level responses is poorly understood. Here we combine optogenetic control of RhoA, live-cell imaging and traction force microscopy to investigate the dynamics of actomyosin-based force generation. Local activation of RhoA not only stimulates local recruitment of actin and myosin but also increased traction forces that rapidly propagate across the cell via stress fibres and drive increased actin flow...

Recent discoveries of striatal GABAergic interneurons require a new conceptualization of the organization of intrastriatal circuitry and their cortical and thalamic inputs. We investigated thalamic inputs to the two populations of striatal neuropeptide Y (NPY) interneurons, plateau low threshold spike (PLTS) and NPY-neurogliaform (NGF) cells. Optogenetic activation of parafascicular inputs evokes suprathreshold monosynaptic glutamatergic excitation in NGF interneurons and a disynaptic, nicotinic excitation through cholinergic interneurons...

Nociception is an evolutionarily conserved mechanism to encode and process harmful environmental stimuli. Like most animals, Drosophila melanogaster larvae respond to a variety of nociceptive stimuli, including noxious touch and temperature, with stereotyped escape responses through activation of multimodal nociceptors. How behavioral responses to these different modalities are processed and integrated by the downstream network remains poorly understood. By combining trans-synaptic labeling, ultrastructural analysis, calcium imaging, optogenetics and behavioral analyses, we uncovered a circuit specific for mechanonociception but not thermonociception...

The mechanisms for acute pain regulation in the brain are not well understood. The prefrontal cortex (PFC) provides top-down control of emotional processes, and it projects to the nucleus accumbens (NAc). This corticostriatal projection forms an important regulatory pathway within the brain's reward system. Recently, this projection has been suggested to control both sensory and affective phenotypes specifically associated with chronic pain. As this projection is also known to play a role in the transition from acute to chronic pain, we hypothesized that this corticostriatal circuit can also exert a modulatory function in the acute pain state...

Ventral midbrain dopamine (DA) is unambiguously involved in motivation and behavioral arousal, yet the contributions of other DA populations to these processes are poorly understood. Here, we demonstrate that the dorsal raphe nucleus DA neurons are critical modulators of behavioral arousal and sleep-wake patterning. Using simultaneous fiber photometry and polysomnography, we observed time-delineated dorsal raphe nucleus dopaminergic (DRN(DA)) activity upon exposure to arousal-evoking salient cues, irrespective of their hedonic valence...

Conventional deep brain stimulation (DBS) of basal ganglia uses high-frequency regular electrical pulses to treat Parkinsonian motor symptoms and has a series of limitations. Relatively new and not yet clinically tested optogenetic stimulation is an effective experimental stimulation technique to affect pathological network dynamics. We compared the effects of electrical and optogenetic stimulation of the basal ganglia on the pathological parkinsonian rhythmic neural activity. We studied the network response to electrical stimulation and excitatory and inhibitory optogenetic stimulations...