Survival of corticostriatal neurons by Rho/Rho-kinase signaling pathway

Change detection in the primate auditory cortex through feedback of prediction error signals

Although cortical feedback signals are essential for modulating feedforward processing, no feedback error signal across hierarchical cortical areas has been reported. Here, we observed such a signal in the auditory cortex of awake common marmoset during an oddball paradigm to induce auditory duration mismatch negativity. Prediction errors to a deviant tone presentation were generated as offset calcium responses of layer 2/3 neurons in the rostral parabelt (RPB) of higher-order auditory cortex, while responses to non-deviant tones were strongly suppressed. Within several hundred milliseconds, the error signals propagated broadly into layer 1 of the primary auditory cortex (A1) and accumulated locally on top of incoming auditory signals. Blockade of RPB activity prevented deviance detection in A1. Optogenetic activation of RPB following tone presentation nonlinearly enhanced A1 tone response. Thus, the feedback error signal is critical for automatic detection of unpredicted stimuli in physiological auditory processing and may serve as backpropagation-like learning.

Anatomical identification of a corticocortical top-down recipient inhibitory circuitry by enhancer-restricted transsynaptic tracing

Despite the importance of postsynaptic inhibitory circuitry targeted by mid/long-range projections (e.g., top-down projections) in cognitive functions, its anatomical properties, such as laminar profile and neuron type, are poorly understood owing to the lack of efficient tracing methods. To this end, we developed a method that combines conventional adeno-associated virus (AAV)-mediated transsynaptic tracing with a distal-less homeobox (Dlx) enhancer-restricted expression system to label postsynaptic inhibitory neurons. We called this method "Dlx enhancer-restricted Interneuron-SpECific transsynaptic Tracing" (DISECT). We applied DISECT to a top-down corticocortical circuit from the secondary motor cortex (M2) to the primary somatosensory cortex (S1) in wild-type mice. First, we injected AAV1-Cre into the M2, which enabled Cre recombinase expression in M2-input recipient S1 neurons. Second, we injected AAV1-hDlx-flex-green fluorescent protein (GFP) into the S1 to transduce GFP into the postsynaptic inhibitory neurons in a Cre-dependent manner. We succeeded in exclusively labeling the recipient inhibitory neurons in the S1. Laminar profile analysis of the neurons labeled via DISECT indicated that the M2-input recipient inhibitory neurons were distributed in the superficial and deep layers of the S1. This laminar distribution was aligned with the laminar density of axons projecting from the M2. We further classified the labeled neuron types using immunohistochemistry and in situ hybridization. This post hoc classification revealed that the dominant top-down M2-input recipient neuron types were somatostatin-expressing neurons in the superficial layers and parvalbumin-expressing neurons in the deep layers. These results demonstrate that DISECT enables the investigation of multiple anatomical properties of the postsynaptic inhibitory circuitry.

Actin-binding protein filamin-A drives tau aggregation and contributes to progressive supranuclear palsy pathology

While amyloid-β lies upstream of tau pathology in Alzheimer's disease, key drivers for other tauopathies, including progressive supranuclear palsy (PSP), are largely unknown. Various tau mutations are known to facilitate tau aggregation, but how the nonmutated tau, which most cases with PSP share, increases its propensity to aggregate in neurons and glial cells has remained elusive. Here, we identified genetic variations and protein abundance of filamin-A in the PSP brains without tau mutations. We provided in vivo biochemical evidence that increased filamin-A levels enhance the phosphorylation and insolubility of tau through interacting actin filaments. In addition, reduction of filamin-A corrected aberrant tau levels in the culture cells from PSP cases. Moreover, transgenic mice carrying human filamin-A recapitulated tau pathology in the neurons. Our data highlight that filamin-A promotes tau aggregation, providing a potential mechanism by which filamin-A contributes to PSP pathology.

Nuclear factor of activated T cells 4 in the prefrontal cortex is required for prophylactic actions of (R)-ketamine

(R, S)-ketamine has prophylactic antidepressant-like effects in rodents; however, the precise molecular mechanisms underlying its action remain unknown. Using RNA-sequencing analysis, we searched novel molecular target(s) that contribute to the prophylactic effects of (R)-ketamine, a more potent enantiomer of (R, S)-ketamine. Pretreatment with (R)-ketamine (10 mg/kg, 6 days before) significantly ameliorated body weight loss, splenomegaly, and increased immobility time of forced swimming test in lipopolysaccharide (LPS: 1.0 mg/kg)-treated mice. RNA-sequencing analysis of prefrontal cortex (PFC) and subsequent IPA (Ingenuity Pathway Analysis) revealed that the nuclear factor of activated T cells 4 (NFATc4) signaling might contribute to sustained prophylactic effects of (R)-ketamine. Quantitative RT-PCR confirmed that (R)-ketamine significantly attenuated the increased gene expression of NFATc4 signaling (Nfatc4, Cd4, Cd79b, H2-ab1, H2-aa) in the PFC of LPS-treated mice. Furthermore, pretreatment with NFAT inhibitors (i.e., NFAT inhibitor and cyclosporin A) showed prophylactic effects in the LPS-treated mice. Similar to (R)-ketamine, gene knockdown of Nfatc4 gene by bilateral injection of adeno-associated virus (AAV) into the mPFC could elicit prophylactic effects in the LPS-treated mice. In conclusion, our data implicate a novel NFATc4 signaling pathway in the PFC underlying the prophylactic effects of (R)-ketamine for inflammation-related depression.

Amygdala Underlies the Environment Dependency of Defense Responses Induced via Superior Colliculus

In our previous study, we showed that the defense responses induced by the selective optogenetic activation of the uncrossed output pathway from the deeper layer of the superior colliculus were environment dependent in the mouse. In a small closed box, the stimulus frequently induced flight (fast forward run away) responses, while in a large open field, the stimulus tended to induce backward retreat responses. We tested a hypothesis that the amygdala is involved in such environment dependency of the innate defense responses. For this purpose, we made a bilateral lesion of the amygdala induced by the ibotenic acid injections in male mice. As a result, in the mice with lesions of substantial portions of the basolateral and basomedial complex, the flight responses in the closed box disappeared and retreat responses were mainly induced. The retreat responses on the open platform were unchanged. Classically, the amygdala has been considered to be involved in the memory-dependent contextual modulation of the fear responses. In contrast, the present results suggest a novel view on the role of the amygdala in which the amygdala plays a key role in sensing the current environmental setting for making a quick decision of action upon emergency, which is critical for survival in the natural environment.

Direct evidence that KNDy neurons maintain gonadotropin pulses and folliculogenesis as the GnRH pulse generator

The gonadotropin-releasing hormone (GnRH) pulse is fundamental for mammalian reproduction: GnRH pulse regimens are needed as therapies for infertile women as continuous GnRH treatment paradoxically inhibits gonadotropin release. Circumstantial evidence suggests that the hypothalamic arcuate KNDy neurons expressing kisspeptin (encoded by Kiss1), neurokinin B (encoded by Tac3), and d ynorphin A serve as a GnRH pulse generator; however, no direct evidence is currently available. Here, we show that rescuing >20% KNDy neurons by transfecting Kiss1 inside arcuate Tac3 neurons, but not outside of these neurons, recovered folliculogenesis and luteinizing hormone (LH) pulses, an indicator of GnRH pulses, in female global Kiss1 knockout (KO) rats and that >90% conditional arcuate Kiss1 KO in newly generated Kiss1-floxed rats completely suppressed LH pulses. These results first provide direct evidence that KNDy neurons are the GnRH pulse generator, and at least 20% of KNDy neurons are sufficient to maintain folliculogenesis via generating GnRH/gonadotropin pulses.

Divergent Whole Brain Projections from the Ventral Midbrain in Macaques

To understand the connectome of the axonal arborizations of dopaminergic midbrain neurons, we investigated the anterograde spread of highly sensitive viral tracers injected into the ventral tegmental area (VTA) and adjacent areas in 3 macaques. In 2 monkeys, injections were centered on the lateral VTA with some spread into the substantia nigra, while in one animal the injection targeted the medial VTA with partial spread into the ventro-medial thalamus. Double-labeling with antibodies against transduced fluorescent proteins (FPs) and tyrosine hydroxylase indicated that substantial portions of transduced midbrain neurons were dopaminergic. Interestingly, cortical terminals were found either homogeneously in molecular layer I, or more heterogeneously, sometimes forming patches, in the deeper laminae II-VI. In the animals with injections in lateral VTA, terminals were most dense in somatomotor cortex and the striatum. In contrast, when the medial VTA was transduced, dense terminals were found in dorsal prefrontal and temporal cortices, while projections to striatum were sparse. In all monkeys, orbitofrontal and occipito-parietal cortex received strong and weak innervation, respectively. Thus, the dopaminergic ventral midbrain sends heterogeneous projections throughout the brain. Furthermore, our results suggest the existence of subgroups in meso-dopaminergic neurons depending on their location in the primate ventral midbrain.

Fast, cell-resolution, contiguous-wide two-photon imaging to reveal functional network architectures across multi-modal cortical areas

Fast and wide field-of-view imaging with single-cell resolution, high signal-to-noise ratio, and no optical aberrations have the potential to inspire new avenues of investigations in biology. However, such imaging is challenging because of the inevitable tradeoffs among these parameters. Here, we overcome these tradeoffs by combining a resonant scanning system, a large objective with low magnification and high numerical aperture, and highly sensitive large-aperture photodetectors. The result is a practically aberration-free, fast-scanning high optical invariant two-photon microscopy (FASHIO-2PM) that enables calcium imaging from a large network composed of ∼16,000 neurons at 7.5 Hz from a 9 mm² contiguous image plane, including more than 10 sensory-motor and higher-order areas of the cerebral cortex in awake mice. Network analysis based on single-cell activities revealed that the brain exhibits small-world rather than scale-free behavior. The FASHIO-2PM is expected to enable studies on biological dynamics by simultaneously monitoring macroscopic activities and their compositional elements.

Lentiviral vector-mediated expression of C3 transferase attenuates retinal ischemia and reperfusion injury in rats

AIMS

Our previous study showed that intravitreal delivery of self-complementary AAV2 (scAAV2)-mediated exoenzyme C3 transferase (C3) can attenuate retinal ischemia/reperfusion (I/R) injury. The current study investigated the neuroprotective effects of lentivirus (LV)-mediated C3 transgene expression on rat retinal I/R injury.

MAIN METHODS

The LV encoding C3 and green fluorescent protein (GFP) together (LV-C3-GFP) or GFP only (LV-GFP) was intravitreally injected to SPRAGUE-DAWLEY rats. On day 5 post-intravitreal injection, eyes were evaluated by slit-lamp examination. The GFP expression on retina was confirmed by in vivo and ex vivo assessments. RhoA GTPase expression in retina was examined by western blot. Retinal I/R injury was generated by transiently increasing intraocular pressure (110 mmHg, 90 min). Eyes were then enucleated, and retinas processed for morphological analysis and TdT-dUTP terminal nick-end labeling (TUNEL) assay.

KEY FINDINGS

No obvious inflammatory reactions or surgical complications were observed after intravitreal injection of LV vectors. There was a significant decrease of total RhoA GTPase level in the retina treated with LV-C3-GFP. Compared to the blank control group, LV-C3-GFP and LV-GFP did not affect the retinal thickness, cell density in ganglion cell layer (GCL), or numbers of apoptotic cells in retinal flat-mounts. In the LV-GFP-treated retinas, I/R decreased the retinal thickness and GCL cell density and increased apoptotic retinal cell numbers. LV-C3-GFP significantly protected against all these degenerative effects of I/R.

SIGNIFICANCE

This study indicated that LV-mediated C3 transgene expression exhibits neuroprotective effects on the retinal I/R injury and holds potential as a novel neuroprotective approach targeting certain retinopathies.

Double viral vector technology for selective manipulation of neural pathways with higher level of efficiency and safety

Pathway-selective gene delivery would be critical for future gene therapy against neuropsychiatric disorders, traumatic neuronal injuries, or neurodegenerative diseases, because the impaired functions depend on neural circuits affected by the insults. Pathway-selective gene delivery can be achieved by double viral vector techniques, which combine an injection of a retrograde transport viral vector into the projection area of the target neurons and that of an anterograde viral vector into their somas. In this study, we tested the efficiency of gene delivery with different combinations of viral vectors to the pathway extending from the ventral tegmental area (VTA) to the cortical motor regions in rats, considered to be critical in the promotion of motor recovery from neural injuries. It was found that retrograde recombinant adeno-associated virus 2-retro (rAAV2reto) combined with anterograde AAVDJ (type2/type4/type5/type8/type9/avian/bovine/caprine chimera) exhibited the highest transduction efficiency in the short term (3-6 weeks) but high toxicity in the long term (3 months). In contrast, the same rAAV2reto combined with anterograde AAV5 displayed moderate transduction efficiency in the short term but low toxicity in the long term. These data suggest that the combination of anterograde AAV5 and retrograde rAAV2retro is suitable for safe and efficient gene delivery to the VTA-cortical pathway.

Activation of ventral CA1 hippocampal neurons projecting to the lateral septum during feeding

A number of studies have reported the involvement of the ventral hippocampus (vHip) and the lateral septum (LS) in negative emotional responses. Besides these well‐documented functions, they are also thought to control feeding behavior. In particular, optogenetic and pharmacogenetic interventions to LS‐projecting vHip neurons have demonstrated that the vHip^→LS neural circuit exerts an inhibition on feeding behavior. However, there have been no reports of vHip neuronal activity during feeding. Here, we focused on LS‐projecting vCA1 neurons (vCA1^→LS) and monitored their activity during feeding behaviors in mice. vCA1^→LS neurons were retrogradely labeled with adeno‐associated virus carrying a ratiometric Ca²⁺ indicator and measured compound Ca²⁺ dynamics by fiber photometry. We first examined vCA1^→LS activity in random food‐exploring behavior and found that vCA1^→LS activation seemed to coincide with food intake; however, our ability to visually confirm this during freely moving behaviors was not sufficiently reliable. We next examined vCA1^→LS activity in a goal‐directed, food‐seeking lever‐press task which temporally divided the mouse state into preparatory, effort, and consummatory phases. We observed vCA1^→LS activation in the postprandial period during the consummatory phase. Such timing‐ and pathway‐specific activation was not observed from pan‐vCA1 neurons. In contrast, reward omission eliminated this activity, indicating that vCA1^→LS activation is contingent on the food reward. Sated mice pressed the lever significantly fewer times but still ate food; however, vCA1^→LS neurons were not activated, suggesting that vCA1^→LS neurons did not respond to habitual behavior. Combined, these results suggest that gastrointestinal interoception rather than food‐intake motions or external sensations are likely to coincide with vCA1^→LS activity. Accordingly, we propose that vCA1^→LS neurons discriminate between matched or unmatched predictive bodily states in which incoming food will satisfy an appetite. We also demonstrate that vCA1^→LS neurons are activated in aversive/anxious situations in an elevated plus maze and tail suspension test. Future behavioral tests utilizing anxious conflict and food intake may reconcile the multiple functions of vCA1^→LS neurons.

Focal loss of the paranodal domain protein Neurofascin155 in the internal capsule impairs cortically induced muscle activity in vivo

Paranodal axoglial junctions are essential for rapid nerve conduction and the organization of axonal domains in myelinated axons. Neurofascin155 (Nfasc155) is a glial cell adhesion molecule that is also required for the assembly of these domains. Previous studies have demonstrated that general ablation of Nfasc155 disorganizes these domains, reduces conduction velocity, and disrupts motor behaviors. Multiple sclerosis (MS), a typical disorder of demyelination in the central nervous system, is reported to have autoantibody to Nfasc. However, the impact of focal loss of Nfasc155, which may occur in MS patients, remains unclear. Here, we examined whether restricted focal loss of Nfasc155 affects the electrophysiological properties of the motor system in vivo. Adeno-associated virus type5 (AAV5) harboring EGFP-2A-Cre was injected into the glial-enriched internal capsule of floxed-Neurofascin (NfascFlox/Flox) mice to focally disrupt paranodal junctions in the cortico-fugal fibers from the motor cortex to the spinal cord. Electromyograms (EMGs) of the triceps brachii muscles in response to electrical stimulation of the motor cortex were successively examined in these awake mice. EMG analysis showed significant delay in the onset and peak latencies after AAV injection compared to control (Nfasc+/+) mice. Moreover, EMG half-widths were increased, and EMG amplitudes were gradually decreased by 13 weeks. Similar EMG changes have been reported in MS patients. These findings provide physiological evidence that motor outputs are obstructed by focal ablation of paranodal junctions in myelinated axons. Our findings may open a new path toward development of a novel biomarker for an early phase of human MS, as Nfasc155 detects microstructural changes in the paranodal junction.

In Vivo Assessment of Cell Death and Nigrostriatal Pathway Integrity Following Continuous Expression of C3 Transferase

The bacterial exoenzyme C3 transferase (C3) irreversibly inhibits RhoA GTPase leading to stimulation of axonal outgrowth in injured neurons. C3 has been used successfully in models of neurotrauma and shows promise as an option to support cell survival and axonal growth of dopaminergic (DA) neurons in Parkinson's disease (PD) cell therapy. Whether the continuous expression of C3 in DA neurons is well-tolerated is unknown. To assess the potential neurotoxicity of sustained expression of C3 in DA neurons, we generated Cre recombinase-dependent adeno-associated viral vectors (AAV) for targeted C3 delivery to DA neurons of the mouse substantia nigra pars compacta (SNc). The effect of continuous expression of C3 on DA neurons was assessed by immunohistochemistry and compared to that of Enhanced Yellow Fluorescent Protein (EYFP) as negative controls. We did not find significant reduction of tyrosine hydroxylase (TH) expression levels nor the presence of cleaved activated caspase 3. Astrocytic activation as determined by GFAP expression was comparable to EYFP controls. To evaluate the impact of C3 expression on striatal terminals of the nigrostriatal pathway, we compared the rotational behavior of wildtype mice injected unilaterally with either C3 or 6-hydroxydopamine (6-OHDA). Mice injected with C3 exhibited similar ipsiversive rotations to the site of injection in comparison to control mice injected with EYFP and significantly fewer ipsiversive rotations compared to 6-OHDA lesioned mice. Non-significant difference between C3 and EYFP controls in behavioral and histological analyses demonstrate that transduced DA neurons express C3 continuously without apparent adverse effects, supporting the use of C3 in efficacy studies targeting DA neurons.

Forelimb movements evoked by optogenetic stimulation of the macaque motor cortex

Optogenetics has become an indispensable tool for investigating brain functions. Although non-human primates are particularly useful models for understanding the functions and dysfunctions of the human brain, application of optogenetics to non-human primates is still limited. In the present study, we generate an effective adeno-associated viral vector serotype DJ to express channelrhodopsin-2 (ChR2) under the control of a strong ubiquitous CAG promoter and inject into the somatotopically identified forelimb region of the primary motor cortex in macaque monkeys. ChR2 is strongly expressed around the injection sites, and optogenetic intracortical microstimulation (oICMS) through a homemade optrode induces prominent cortical activity: Even single-pulse, short-duration oICMS evokes long-lasting repetitive firings of cortical neurons. In addition, oICMS elicits distinct forelimb movements and muscle activity, which are comparable to those elicited by conventional electrical ICMS. The present study removes obstacles to optogenetic manipulation of neuronal activity and behaviors in non-human primates.

Non-human primates are useful models for understanding the human brain but application of optogenetics to non-human primates is challenging. The authors used optogenetic intracortical microstimulation in the primary motor cortex of macaques to elicit distinct forelimb movements and muscle activity.

Structural dynamics and stability of corticocortical and thalamocortical axon terminals during motor learning

Synaptic plasticity is the cellular basis of learning and memory. When animals learn a novel motor skill, synaptic modifications are induced in the primary motor cortex (M1), and new postsynaptic dendritic spines relevant to motor memory are formed in the early stage of learning. However, it is poorly understood how presynaptic axonal boutons are formed, eliminated, and maintained during motor learning, and whether long-range corticocortical and thalamocortical axonal boutons show distinct structural changes during learning. In this study, we conducted two-photon imaging of presynaptic boutons of long-range axons in layer 1 (L1) of the mouse M1 during the 7-day learning of an accelerating rotarod task. The training-period-averaged rate of formation of boutons on axons projecting from the secondary motor cortical area increased, while the average rate of elimination of those from the motor thalamus (thalamic boutons) decreased. In particular, the elimination rate of thalamic boutons during days 4-7 was lower than that in untrained mice, and the fraction of pre-existing thalamic boutons that survived until day 7 was higher than that in untrained mice. Our results suggest that the late stabilization of thalamic boutons in M1 contributes to motor skill learning.

Gene delivery to cone photoreceptors by subretinal injection of rAAV2/6 in the mouse retina

Adeno-associated virus (AAV) has been studied as a safe delivery tool for gene therapy of retinal blinding diseases such as Leber's congenital amaurosis (LCA). The tropism of recombinant AAV (rAAV) including its specificity and efficiency in targeting retinal cell types has been studied with native or engineered capsids, along with specific promoters. However, one of the rAAV serotypes, rAAV2/6, has not been well-studied based on a report of low infection efficiency in the retina. We investigated the tropism of several rAAVs by subretinal injection in the adult mouse and found that rAAV2/6 predominantly infected cone photoreceptors including the main spectral type. Our data suggest that subretinal injection with rAAV2/6 may provide both an efficacious and specific means of gene delivery to cone photoreceptors in murine retinas.

GABAergic neurons in the olfactory cortex projecting to the lateral hypothalamus in mice

Olfaction guides goal-directed behaviours including feeding. To investigate how central olfactory neural circuits control feeding behaviour in mice, we performed retrograde tracing from the lateral hypothalamus (LH), an important feeding centre. We observed a cluster of retrogradely labelled cells distributed in the posteroventral region of the olfactory peduncle. Histochemical analyses revealed that the majority of these retrogradely labelled projection neurons expressed glutamic acid decarboxylase 65/67 (GAD65/67), but not vesicular glutamate transporter 1 (VGluT1). We named this region containing GABAergic projection neurons the ventral olfactory nucleus (VON) to differentiate it from the conventional olfactory peduncle. VON neurons were less immunoreactive for DARPP-32, a striatal neuron marker, compared to neurons in the olfactory tubercle and nucleus accumbens, which distinguished the VON from the ventral striatum. Fluorescent labelling confirmed putative synaptic contacts between VON neurons and olfactory bulb projection neurons. Rabies-virus-mediated trans-synaptic labelling revealed that VON neurons received synaptic inputs from the olfactory bulb, other olfactory cortices, horizontal limb of the diagonal band, and prefrontal cortex. Collectively, these results identify novel GABAergic projection neurons in the olfactory cortex that may integrate olfactory sensory and top-down inputs and send inhibitory output to the LH, which may modulate odour-guided LH-related behaviours.

Impaired cortico-striatal excitatory transmission triggers epilepsy

STXBP1 and SCN2A gene mutations are observed in patients with epilepsies, although the circuit basis remains elusive. Here, we show that mice with haplodeficiency for these genes exhibit absence seizures with spike-and-wave discharges (SWDs) initiated by reduced cortical excitatory transmission into the striatum. Mice deficient for Stxbp1 or Scn2a in cortico-striatal but not cortico-thalamic neurons reproduce SWDs. In Stxbp1 haplodeficient mice, there is a reduction in excitatory transmission from the neocortex to striatal fast-spiking interneurons (FSIs). FSI activity transiently decreases at SWD onset, and pharmacological potentiation of AMPA receptors in the striatum but not in the thalamus suppresses SWDs. Furthermore, in wild-type mice, pharmacological inhibition of cortico-striatal FSI excitatory transmission triggers absence and convulsive seizures in a dose-dependent manner. These findings suggest that impaired cortico-striatal excitatory transmission is a plausible mechanism that triggers epilepsy in Stxbp1 and Scn2a haplodeficient mice.

Spike and wave discharge (SWD) activity is seen during absence seizures and is thought to be thalamocortical in origin. Here, the authors show that SWDs are initiated through the impaired corticostriatal excitatory transmissions onto striatal fast spiking interneurons.

Opposing Roles of Dopamine Receptor D1- and D2-Expressing Neurons in the Anteromedial Olfactory Tubercle in Acquisition of Place Preference in Mice

Olfaction induces adaptive motivated behaviors. Odors associated with food induce attractive behavior, whereas those associated with dangers induce aversive behavior. We previously reported that learned odor-induced attractive and aversive behaviors accompany activation of the olfactory tubercle (OT) in a domain- and cell type-specific manner. Odor cues associated with a sugar reward induced attractive behavior and c-fos expression in the dopamine receptor D1-expressing neurons (D1 neurons) in the anteromedial OT. In contrast, odor cues associated with electrical shock induced aversive behavior and c-fos expression in the pamine receptor D2-expressing neurons (D2 neurons) in the anteromedial OT, as well as the D1 neurons in the lateral OT. Here, we investigated whether the D1 and D2 neurons in the anteromedial OT play distinct roles in attractive or aversive behaviors, using optogenetic stimulation and real-time place preference (RTPP) tests. Mice expressing ChETA (ChR2/E123T)-enhanced yellow fluorescent protein (EYFP) in the D1 neurons in the anteromedial OT spent a longer time in the photo-stimulation side of the place preference chamber than the control mice expressing EYFP. On the other hand, upon optogenetic stimulation of the D2 neurons in the anteromedial OT, the mice spent a shorter time in the photo-stimulation side than the control mice. Local neural activation in the anteromedial OT during the RTPP tests was confirmed by c-fos mRNA expression. These results suggest that the D1 and D2 neurons in the anteromedial OT play opposing roles in attractive and aversive behaviors, respectively.

Sensory nerve supports epithelial stem cell function in healing of corneal epithelium in mice: the role of trigeminal nerve transient receptor potential vanilloid 4

In order to understand the pathobiology of neurotrophic keratopathy, we established a mouse model by coagulating the first branch of the trigeminal nerve (V1 nerve). In our model, the sensory nerve in the central cornea disappeared and remaining fibers were sparse in the peripheral limbal region. Impaired corneal epithelial healing in the mouse model was associated with suppression of both cell proliferation and expression of stem cell markers in peripheral/limbal epithelium as well as a reduction of transient receptor potential vanilloid 4 (TRPV4) expression in tissue. TRPV4 gene knockout also suppressed epithelial repair in mouse cornea, although it did not seem to directly modulate migration of epithelium. In a co-culture experiment, TRPV4-introduced KO trigeminal ganglion upregulated nerve growth factor (NGF) in cultured corneal epithelial cells, but ganglion with a control vector did not. TRPV4 gene introduction into a damaged V1 nerve rescues the impairment of epithelial healing in association with partial recovery of the stem/progenitor cell markers and upregulation of cell proliferation and of NGF expression in the peripheral/limbal epithelium. Gene transfer of TRPV4 did not accelerate the regeneration of nerve fibers. Sensory nerve TRPV4 is critical to maintain stemness of peripheral/limbal basal cells, and is one of the major mechanisms of homeostasis maintenance of corneal epithelium.

Overexpression of miR-582-5p Inhibits the Apoptosis of Neuronal Cells after Cerebral Ischemic Stroke Through Regulating PAR-1/Rho/Rho Axis

OBJECTIVE

The purpose of this study was to explore the role of miR-582-5p/proteinase-activated receptors type I (PAR-1)/Rho/Rho in neuronal cell apoptosis after cerebral ischemic stroke (CIS).

METHODS

In vivo mouse model of CIS induced by middle cerebral artery occlusion and in vitro model induced by oxygen-glucose deprivation/reoxygenation (OGD/R) in N2A cells was established. The expressions of miR-582-5p, PAR-1, RhoA, and ROCKII in brain tissues and N2A cells were detected. Neuronal cell apoptosis was detected by flow cytometry.

RESULTS

We found that miR-582-5p expression was decreased and the expressions of PAR-1, RhoA, and ROCKII were increased in CIS mice and OGD/R model. Moreover, miR-582-5p negatively regulated PAR-1, and overexpression of miR-582-5p inhibited the activation of Rho/Rho pathway by downregulating PAR-1, thus reducing OGD/R-induced neuronal cell apoptosis.

CONCLUSIONS

Our results suggested that miR-582-5p overexpression could regulate Rho/Rho-kinase signaling pathway via targeting PAR-1, thereby governing the apoptosis of neuronal cells after CIS.

Super-wide-field two-photon imaging with a micro-optical device moving in post-objective space

Wide-field imaging of neural activity at a cellular resolution is a current challenge in neuroscience. To address this issue, wide-field two-photon microscopy has been developed; however, the field size is limited by the objective size. Here, we develop a micro-opto-mechanical device that rotates within the post-objective space between the objective and brain tissue. Two-photon microscopy with this device enables sub-second sequential calcium imaging of left and right mouse sensory forelimb areas 6 mm apart. When imaging the rostral and caudal motor forelimb areas (RFA and CFA) 2 mm apart, we found high pairwise correlations in spontaneous activity between RFA and CFA neurons and between an RFA neuron and its putative axons in CFA. While mice performed a sound-triggered forelimb-movement task, the population activity between RFA and CFA covaried across trials, although the field-averaged activity was similar across trials. The micro-opto-mechanical device in the post-objective space provides a novel and flexible design to clarify the correlation structure between distant brain areas at subcellular and population levels.

Dysregulation of schizophrenia-related aquaporin 3 through disruption of paranode influences neuronal viability

Myelinated axons segregate the axonal membrane into four defined regions: the node of Ranvier, paranode, juxtaparanode, and internode. The paranodal junction consists of specific component proteins, such as neurofascin155 (NF155) on the glial side, and Caspr and Contactin on the axonal side. Although paranodal junctions are thought to play crucial roles in rapid saltatory conduction and nodal assembly, the role of their interaction with neurons is not fully understood. In a previous study, conditional NF155 knockout in oligodendrocytes led to disorganization of the paranodal junctions. To examine if disruption of paranodal junctions affects neuronal gene expression, we prepared total RNA from the retina of NF155 conditional knockout, and performed expression analysis. We found that the expression level of 433 genes changed in response to paranodal junction ablation. Interestingly, expression of aquaporin 3 (AQP3) was significantly reduced in NF155 conditional knockout mice, but not in cerebroside sulfotransferase knockout (CST-KO) mice, whose paranodes are not originally formed during development. Copy number variations have an important role in the etiology of schizophrenia (SCZ). We observed rare duplications of AQP3 in SCZ patients, suggesting a correlation between abnormal AQP3 expression and SCZ. To determine if AQP3 over-expression in NF155 conditional knockout mice influences neuronal function, we performed adeno-associated virus (AAV)-mediated over-expression of AQP3 in the motor cortex of mice and found a significant increase in caspase 3-dependent neuronal apoptosis in AQP3-transduced cells. This study may provide new insights into therapeutic approaches for SCZ by regulating AQP3 expression, which is associated with paranodal disruption.

In vivo wide-field calcium imaging of mouse thalamocortical synapses with an 8 K ultra-high-definition camera

In vivo wide-field imaging of neural activity with a high spatio-temporal resolution is a challenge in modern neuroscience. Although two-photon imaging is very powerful, high-speed imaging of the activity of individual synapses is mostly limited to a field of approximately 200 µm on a side. Wide-field one-photon epifluorescence imaging can reveal neuronal activity over a field of ≥1 mm2 at a high speed, but is not able to resolve a single synapse. Here, to achieve a high spatio-temporal resolution, we combine an 8 K ultra-high-definition camera with spinning-disk one-photon confocal microscopy. This combination allowed us to image a 1 mm2 field with a pixel resolution of 0.21 µm at 60 fps. When we imaged motor cortical layer 1 in a behaving head-restrained mouse, calcium transients were detected in presynaptic boutons of thalamocortical axons sparsely labeled with GCaMP6s, although their density was lower than when two-photon imaging was used. The effects of out-of-focus fluorescence changes on calcium transients in individual boutons appeared minimal. Axonal boutons with highly correlated activity were detected over the 1 mm2 field, and were probably distributed on multiple axonal arbors originating from the same thalamic neuron. This new microscopy with an 8 K ultra-high-definition camera should serve to clarify the activity and plasticity of widely distributed cortical synapses.

Distinct Roles of Ventromedial versus Ventrolateral Striatal Medium Spiny Neurons in Reward-Oriented Behavior

The ventral striatum (VS) is a key brain center regulating reward-oriented behavior [1-4]. The VS can be anatomically divided into medial (VMS) and lateral (VLS) portions based on cortical input patterns. The VMS receives inputs from medial pallium-originated limbic structures (e.g., the medial prefrontal cortex [mPFC]), and the VLS receives inputs from the lateral pallium-originated areas (e.g., the insula) [5, 6]. This anatomical feature led us to hypothesize a functional segregation within the VS in terms of the regulation of reward-oriented behavior. Here, we engineered a fiber photometry system [4] and monitored population-level Ca²⁺ activities of dopamine D2-receptor-expressing medium spiny neurons (D2-MSNs), one of the major cell types in the striatum, during a food-seeking discrimination task. We found that VLS D2-MSNs were activated at the time of cue presentation. In stark contrast, VMS D2-MSNs were inhibited at this time point. Optogenetic counteraction of those changes in the VLS and VMS impaired action initiation and increased responding toward non-rewarded cues, respectively. During lever-press reversal training, VMS inhibition at the time of cue presentation temporarily ceased and optogenetic activation of VMS D2-MSNs facilitated acquisition of the new contingency. These data indicate that the opposing inhibition and excitation in VMS and VLS are important for selecting and initiating a proper action in a reward-oriented behavior. We propose distinct subregional roles within the VS in the execution of successful reward-oriented behavior.

Two-photon calcium imaging of the medial prefrontal cortex and hippocampus without cortical invasion

In vivo two-photon calcium imaging currently allows us to observe the activity of multiple neurons up to ~900 µm below the cortical surface without cortical invasion. However, many important brain areas are located deeper than this. Here, we used an 1100 nm laser that underfilled the back aperture of the objective together with red genetically encoded calcium indicators to establish two-photon calcium imaging of the intact mouse brain and detect neural activity up to 1200 μm from the cortical surface. This imaging was obtained from the medial prefrontal cortex (the prelimbic area) and the hippocampal CA1 region. We found that neural activity before water delivery repeated at a constant interval was higher in the prelimbic area than in layer 2/3 of the secondary motor area. Reducing the invasiveness of imaging is an important strategy to reveal the intact brain processes active in cognition and memory.

PTPRJ Inhibits Leptin Signaling, and Induction of PTPRJ in the Hypothalamus Is a Cause of the Development of Leptin Resistance

Leptin signaling in the hypothalamus plays a crucial role in the regulation of body weight. Leptin resistance, in which leptin signaling is disrupted, is a major obstacle to the improvement of obesity. We herein demonstrated that protein tyrosine phosphatase receptor type J (Ptprj) is expressed in hypothalamic neurons together with leptin receptors, and that PTPRJ negatively regulates leptin signaling by inhibiting the activation of JAK2, the primary tyrosine kinase in leptin signaling, through the dephosphorylation of Y813 and Y868 in JAK2 autophosphorylation sites. Leptin signaling is enhanced in Ptprj-deficient mice, and they exhibit lower weight gain than wild-type mice because of a reduced food intake. Diet-induced obesity and the leptin treatment up-regulated PTPRJ expression in the hypothalamus, while the overexpression of PTPRJ induced leptin resistance. Thus, the induction of PTPRJ is a factor contributing to the development of leptin resistance, and the inhibition of PTPRJ may be a potential strategy for improving obesity.

Pseudotyped Lentiviral Vectors for Retrograde Gene Delivery into Target Brain Regions

Gene transfer through retrograde axonal transport of viral vectors offers a substantial advantage for analyzing roles of specific neuronal pathways or cell types forming complex neural networks. This genetic approach may also be useful in gene therapy trials by enabling delivery of transgenes into a target brain region distant from the injection site of the vectors. Pseudotyping of a lentiviral vector based on human immunodeficiency virus type 1 (HIV-1) with various fusion envelope glycoproteins composed of different combinations of rabies virus glycoprotein (RV-G) and vesicular stomatitis virus glycoprotein (VSV-G) enhances the efficiency of retrograde gene transfer in both rodent and nonhuman primate brains. The most recently developed lentiviral vector is a pseudotype with fusion glycoprotein type E (FuG-E), which demonstrates highly efficient retrograde gene transfer in the brain. The FuG-E–pseudotyped vector permits powerful experimental strategies for more precisely investigating the mechanisms underlying various brain functions. It also contributes to the development of new gene therapy approaches for neurodegenerative disorders, such as Parkinson’s disease, by delivering genes required for survival and protection into specific neuronal populations. In this review article, we report the properties of the FuG-E–pseudotyped vector, and we describe the application of the vector to neural circuit analysis and the potential use of the FuG-E vector in gene therapy for Parkinson’s disease.