Explore the vast range of titles available.

The basolateral amygdala (BLA) and ventral hippocampal CA1 (vCA1) are cellularly and functionally diverse along their anterior–posterior and superficial-deep axes. Here, we find that anterior BLA (aBLA) and posterior BLA (pBLA) innervate deep-layer calbindin1-negative (Calb1−) and superficial-layer calbindin1-positive neurons (Calb1+) in vCA1, respectively. Photostimulation of pBLA–vCA1 inputs has an anxiolytic effect in mice, promoting approach behaviours during conflict exploratory tasks. By contrast, stimulating aBLA–vCA1 inputs induces anxiety-like behaviour resulting in fewer approaches. During conflict stages of the elevated plus maze task vCA1 Calb1+ neurons are preferentially activated at the open-to-closed arm transition, and photostimulation of vCA1 Calb1+ neurons at decision-making zones promotes approach with fewer retreats. In the APP/PS1 mouse model of Alzheimer’s disease, which shows anxiety-like behaviour, photostimulating the pBLA–vCA1 Calb1+ circuit ameliorates the anxiety in a Calb1-dependent manner. These findings suggest the pBLA–vCA1 Calb1+ circuit from heterogeneous BLA–vCA1 connections drives approach behaviour to reduce anxiety-like behaviour. Projections from the anterior and posterior basolateral amygdala (pBLA) to the ventral hippocampus CA1 (vCA1) are heterogenous. Here the authors show that activating the pathway from pBLA to vCA1 calbindin 1 positive neurons has an anxiolytic effect in approach-avoidance tasks in mice.

Significance Ca ²⁺ ions serve as a key cellular signal and are tightly controlled. One mechanism to limit free Ca ²⁺ ions is buffering by Ca ²⁺-binding proteins, which are strongly expressed in sensory hair cells of the ear. Here we studied how genetic disruption of the Ca ²⁺-binding proteins parvalbumin-α, calbindin-D28k, and calretinin affects exocytosis and sound encoding at the synapses of mouse inner hair cells (IHCs) and spiral ganglion neurons (SGNs). Mutant IHCs showed increased exocytosis, but the sound-evoked spiking activity in SGNs was unaltered. Together with mathematical modeling, this finding indicates that a large fraction of exocytosis in mutant IHCs occurred outside synapses. We conclude that Ca ²⁺-binding proteins shape presynaptic Ca ²⁺ signals to restrict exocytosis to active zones, thus enabling metabolically efficient sound encoding. EF-hand Ca ²⁺-binding proteins are thought to shape the spatiotemporal properties of cellular Ca ²⁺ signaling and are prominently expressed in sensory hair cells in the ear. Here, we combined genetic disruption of parvalbumin-α, calbindin-D28k, and calretinin in mice with patch-clamp recording, in vivo physiology, and mathematical modeling to study their role in Ca ²⁺ signaling, exocytosis, and sound encoding at the synapses of inner hair cells (IHCs). IHCs lacking all three proteins showed excessive exocytosis during prolonged depolarizations, despite enhanced Ca ²⁺-dependent inactivation of their Ca ²⁺ current. Exocytosis of readily releasable vesicles remained unchanged, in accordance with the estimated tight spatial coupling of Ca ²⁺ channels and release sites (effective “coupling distance” of 17 nm). Substitution experiments with synthetic Ca ²⁺ chelators indicated the presence of endogenous Ca ²⁺ buffers equivalent to 1 mM synthetic Ca ²⁺-binding sites, approximately half of them with kinetics as fast as 1,2-Bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA). Synaptic sound encoding was largely unaltered, suggesting that excess exocytosis occurs extrasynaptically. We conclude that EF-hand Ca ²⁺ buffers regulate presynaptic IHC function for metabolically efficient sound coding.

Protein folding is governed by non-covalent interactions under the benefits and constraints of the covalent linkage of the backbone chain. In the current work we investigate the influence of loop length variation on the free energies of folding and ligand binding in a small globular single-domain protein containing two EF-hand subdomains—calbindin D 9k . We introduce a linker extension between the subdomains and vary its length between 1 to 16 glycine residues. We find a close to linear relationship between the linker length and the free energy of folding of the Ca 2+ -free protein. In contrast, the linker length has only a marginal effect on the Ca 2+ affinity and cooperativity. The variant with a single-glycine extension displays slightly increased Ca 2+ affinity, suggesting that the slightly extended linker allows optimized packing of the Ca 2+ -bound state. For the extreme case of disconnected subdomains, Ca 2+ binding becomes coupled to folding and assembly. Still, a high affinity between the EF-hands causes the non-covalent pair to retain a relatively high apparent Ca 2+ affinity. Our results imply that loop length variation could be an evolutionary option for modulating properties such as protein stability and turnover without compromising the energetics of the specific function of the protein.

Rabies virus (RABV) infection leads to a fatal neurological outcome in humans and animals and is associated with major alterations in cellular gene expression. In this study, we describe the effects of RABV infection on the mRNA expression levels of two genes, encoding the Ca2+-binding proteins (Ca-BPs) calbindin D-28K (Calb1) and calretinin (Calb2), in the brains of BALB/c mice. Sixty 4-week-old mice were divided into two test groups and one control group. Mice were inoculated intramuscularly with either a street rabies virus (SRV) strain or a challenge virus standard (CVS-11) strain and sacrificed at 3-day intervals up to day 18 postinfection. A direct fluorescent antibody test (DFAT) was used to verify the presence of RABV antigen in brain tissues, and real-time quantitative PCR (RT-PCR) was used to assess gene expression. Infection with both RABV strains resulted in significant (p < 0.05) increases in Calb1 and Calb2 expression in the test animals when compared with the controls at various time points in the study. Correlation analysis indicated very weak insignificant (p > 0.05) negative and positive relationships, respectively, between Calb1 expression (r = -0.04) and Calb2 expression (r = 0.08) with viral load (CVS-11 strain). Insignificant (p > 0.05) relationships were also observed Calb1 expression (r = -0.28) and Calb2 expression (r = 0.06) and viral load for the SRV strain.The observed alterations in Calb1 and Calb2 expression in this study indicate possible impairments in neuronal Ca2+ buffering and Ca2+ homeostasis as a result of RABV infection and, consequently, possible involvement of calbindin-D28K and calretinin in the neuropathogenesis of rabies.

The “non-specific” ventromedial thalamic nucleus (VM) has long been considered a candidate for mediating cortical arousal due to its diffuse, superficial projections, but direct evidence was lacking. Here, we show in mice that the activity of VM calbindin1-positive matrix cells is high in wake and REM sleep and low in NREM sleep, and increases before cortical activity at the sleep-to-wake transition. Optogenetic stimulation of VM cells rapidly awoke all mice from NREM sleep and consistently caused EEG activation during slow wave anesthesia, while arousal did not occur from REM sleep. Conversely, chemogenetic inhibition of VM decreased wake duration. Optogenetic activation of the “specific” ventral posteromedial nucleus (VPM) did not cause arousal from either NREM or REM sleep. Thus, matrix cells in VM produce arousal and broad cortical activation during NREM sleep and slow wave anesthesia in a way that accounts for the effects classically attributed to “non-specific” thalamic nuclei. The ventromedial thalamus (VM) is thought to control cortical arousal through its diffuse projections to cortex. Here the authors record and manipulate the activity of calbindin1-positive matrix cells in VM and show that they bidirectionally regulate the sleep-wake transition.

Little is known about how microcircuits are organized in layer 2 of the medial entorhinal cortex. We visualized principal cell microcircuits and determined cellular theta-rhythmicity in freely moving rats. Non–dentate-projecting, calbindin-positive pyramidal cells bundled dendrites together and formed patches arranged in a hexagonal grid aligned to layer 1 axons, parasubiculum, and cholinergic inputs. Calbindin-negative, dentate-gyrus–projecting stellate cells were distributed across layer 2 but avoided centers of calbindin-positive patches. Cholinergic drive sustained theta-rhythmicity, which was twofold stronger in pyramidal than in stellate neurons. Theta-rhythmicity was cell-type–specific but not distributed as expected from cell-intrinsic properties. Layer 2 divides into a weakly theta-locked stellate cell lattice and spatiotemporally highly organized pyramidal grid. It needs to be assessed how these two distinct principal cell networks contribute to grid cell activity.

The retinoic acid derivative fenretinide (FR) is capable of transdifferentiating cultured retinal pigment epithelial (RPE) cells towards a neuronal-like phenotype, but the underlying mechanisms are not understood. To identify genes involved in this process we performed a microarray analysis of RPE cells pre- and post-FR treatment, and observed a marked down-regulation of AnnexinA8 (AnxA8) in transdifferentiated cells. To determine whether AnxA8 plays a role in maintaining RPE cell phenotype we directly manipulated AnxA8 expression in cultured and primary RPE cells using siRNA-mediated gene suppression, and over-expression of AnxA8-GFP in conjunction with exposure to FR. Treatment of RPE cells with AnxA8 siRNA recapitulated exposure to FR, with cell cycle arrest, neuronal transdifferentiation, and concomitant up-regulation of the neuronal markers calretinin and calbindin, as assessed by real-time PCR and immunofluorescence. In contrast, AnxA8 transient over-expression in ARPE-19 cells prevented FR-induced differentiation. Ectopic expression of AnxA8 in AnxA8-depleted cells led to decreased neuronal marker staining, and normal cell growth as judged by phosphohistone H3 staining, cell counting and cleaved caspase-3 levels. These data show that down-regulation of AnxA8 is both necessary and sufficient for neuronal transdifferentiation of RPE cells and reveal an essential role for AnxA8 as a key regulator of RPE phenotype.

Most sensory information destined for the neocortex is relayed through the thalamus, where considerable transformation occurs 1 , 2 . One means of transformation involves interactions between excitatory thalamocortical neurons that carry data to the cortex and inhibitory neurons of the thalamic reticular nucleus (TRN) that regulate the flow of those data 3 – 6 . Although the importance of the TRN has long been recognised 7 – 9 , understanding of its cell types, their organization and their functional properties has lagged behind that of the thalamocortical systems they control. Here we address this by investigating the somatosensory and visual circuits of the TRN in mice. In the somatosensory TRN we observed two groups of genetically defined neurons that are topographically segregated and physiologically distinct, and that connect reciprocally with independent thalamocortical nuclei through dynamically divergent synapses. Calbindin-expressing cells—located in the central core—connect with the ventral posterior nucleus, the primary somatosensory thalamocortical relay. By contrast, somatostatin-expressing cells—which reside along the surrounding edges of the TRN—synapse with the posterior medial thalamic nucleus, a higher-order structure that carries both top-down and bottom-up information 10 – 12 . The two TRN cell groups process their inputs in pathway-specific ways. Synapses from the ventral posterior nucleus to central TRN cells transmit rapid excitatory currents that depress deeply during repetitive activity, driving phasic spike output. Synapses from the posterior medial thalamic nucleus to edge TRN cells evoke slower, less depressing excitatory currents that drive more persistent spiking. Differences in the intrinsic physiology of TRN cell types, including state-dependent bursting, contribute to these output dynamics. The processing specializations of these two somatosensory TRN subcircuits therefore appear to be tuned to the signals they carry—a primary central subcircuit tuned to discrete sensory events, and a higher-order edge subcircuit tuned to temporally distributed signals integrated from multiple sources. The structure and function of visual TRN subcircuits closely resemble those of the somatosensory TRN. These results provide insights into how subnetworks of TRN neurons may differentially process distinct classes of thalamic information. In the thalamic reticular nucleus there are two neuron types that are segregated into central and edge zones and receive inputs from different thalamocortical nuclei, creating subcircuits with distinct dynamics.

The incidence rates of light-induced retinopathies have increased significantly in the last decades because of continuous exposure to light from different electronic devices. Recent studies showed that exposure to blue light had been related to the pathogenesis of light-induced retinopathies. However, the pathophysiological mechanisms underlying changes induced by light exposure are not fully known yet. In the present study, the effects of exposure to light at different wavelengths with emission peaks in the blue light range (400–500 nm) on the localization of Calretinin-N18 (CaR-N18) and Calbindin-D28K (CaB-D28K) in adult zebrafish retina are studied using double immunofluorescence with confocal laser microscopy. CaB-D28K and CaR-N18 are two homologous cytosolic calcium-binding proteins (CaBPs) implicated in essential process regulation in central and peripheral nervous systems. CaB-D28K and CaR-N18 distributions are investigated to elucidate their potential role in maintaining retinal homeostasis under distinct light conditions and darkness. The results showed that light influences CaB-D28K and CaR-N18 distribution in the retina of adult zebrafish, suggesting that these CaBPs could be involved in the pathophysiology of retinal damage induced by the short-wavelength visible light spectrum.

Compelling evidence links age-related brain dysfunction and neurodegenerative processes to persistent disruptions in intracellular calcium (Ca 2+ ) signaling, a central hypothesis in the Ca 2+ theory of aging. Calbindin (CB), a classical Ca 2+ buffer, has been implicated in region-specific susceptibility to aging-related effects. Specifically, CB-immunopositive (CB + ) neurons have demonstrated an age-dependent decline in neuronal number across various cortical and subcortical regions. However, it remains unclear whether this decrease occur in the dorsal lateral geniculate nucleus (DLG), a crucial relay and modulatory center for visual processing. Additionally, the potential impact of aging on the cellular volume of CB + neurons in the DLG has not been fully elucidated, albeit an age-dependent neuronal hypertrophy of this region has been reported. To address these questions, we investigated CB + neurons in the DLG of six marmosets ( Callithrix jacchus ), aged between 29–143 months. Using design-based stereological techniques, we estimated the total number and somal volume of CB + neurons in DLG layers. Our results revealed no signs of CB + neuronal number loss and somal volumetric changes in aged DLG, particularly within the koniocellular layers, a stratum that primarily expresses CB and play a critical role in blue/yellow color vision. Altogether, our findings suggest a preserved neuronal number and cellular volume of the CB + population during aging process in the marmoset DLG. Moreover, they provide a valuable basis for future investigations into the neuroprotective role of CB in visual processing during aging and open avenues for strategies designed to preserve vulnerable neuronal populations in age-related neurodegenerative conditions.