Reciprocal Connections between Parvalbumin-Expressing Cells and Adjacent Pyramidal Cells Are Regulated by Clustered Protocadherin γ.

Functional neural circuits in the cerebral cortex are established through specific neural connections between excitatory and various inhibitory cell types. However, the molecular mechanisms underlying synaptic partner recognition remain unclear. In this study, we examined the impact of clustered protocadherin-γ () gene deletion in parvalbumin-positive (PV) cells on intralaminar and translaminar neural circuits formed between PV and pyramidal (Pyr) cells in the primary visual cortex (V1) of male and female mice.

Visualization of homophilic interaction of clustered protocadherin in neurons.

Clustered protocadherin (Pcdh) functions as a cell recognition molecule through the homophilic interaction in the central nervous system. However, its interactions have not yet been visualized in neurons. We previously reported PcdhγB2-Förster resonance energy transfer (FRET) probes to be applicable only to cell lines.

Microglia enable cross-modal plasticity by removing inhibitory synapses.

Cross-modal plasticity is the repurposing of brain regions associated with deprived sensory inputs to improve the capacity of other sensory modalities. The functional mechanisms of cross-modal plasticity can indicate how the brain recovers from various forms of injury and how different sensory modalities are integrated. Here, we demonstrate that rewiring of the microglia-mediated local circuit synapse is crucial for cross-modal plasticity induced by visual deprivation (monocular deprivation [MD]).

CTCF loss induces giant lamellar bodies in Purkinje cell dendrites.

CCCTC-binding factor (CTCF) has a key role in higher-order chromatin architecture that is important for establishing and maintaining cell identity by controlling gene expression. In the mature cerebellum, CTCF is highly expressed in Purkinje cells (PCs) as compared with other cerebellar neurons. The cerebellum plays an important role in motor function by regulating PCs, which are the sole output neurons, and defects in PCs cause motor dysfunction.

Time-resolved neurotransmitter detection in mouse brain tissue using an artificial intelligence-nanogap.

The analysis of neurotransmitters in the brain helps to understand brain functions and diagnose Parkinson's disease. Pharmacological inhibition experiments, electrophysiological measurement of action potentials, and mass analysers have been applied for this purpose; however, these techniques do not allow direct neurotransmitter detection with good temporal resolution by using nanometre-sized electrodes. Hence, we developed a method for direct observation of a single neurotransmitter molecule with a gap width of ≤ 1 nm and on the millisecond time scale.

miR-124 dosage regulates prefrontal cortex function by dopaminergic modulation.

MicroRNA-124 (miR-124) is evolutionarily highly conserved among species and one of the most abundantly expressed miRNAs in the developing and mature central nervous system (CNS). Previous studies reported that miR-124 plays a role in CNS development, such as neuronal differentiation, maturation, and survival. However, the role of miR-124 in normal brain function has not yet been revealed.

Clustered Protocadherins Are Required for Building Functional Neural Circuits.

Neuronal identity is generated by the cell-surface expression of clustered protocadherin (Pcdh) isoforms. In mice, 58 isoforms from three gene clusters, αβ, and γ, are differentially expressed in neurons. Since -heteromeric Pcdh oligomers on the cell surface interact homophilically with that in other neurons , it has been thought that the Pcdh isoform repertoire determines the binding specificity of synapses.

Establishment of high reciprocal connectivity between clonal cortical neurons is regulated by the Dnmt3b DNA methyltransferase and clustered protocadherins.

Background: The specificity of synaptic connections is fundamental for proper neural circuit function. Specific neuronal connections that underlie information processing in the sensory cortex are initially established without sensory experiences to a considerable extent, and then the connections are individually refined through sensory experiences. Excitatory neurons arising from the same single progenitor cell are preferentially connected in the postnatal cortex, suggesting that cell lineage contributes to the initial wiring of neurons.

Ni(2+)-sensitive T-type Ca(2+) channel currents are regulated in parallel with synaptic and visual response plasticity in visual cortex.

Visual cortical neurons undergo depression and potentiation of their visual responses to stimulation of the deprived and non-deprived eyes, respectively, after monocular deprivation. This modification occurs predominantly during an early postnatal period in normal development, and this critical period is postponed until adulthood in animals reared in darkness from birth. We have proposed that Ni(2+)-sensitive T-type Ca(2+) channel-dependent long-term potentiation (T-LTP) mediates the potentiation of non-deprived eye responses.

Developmental epigenetic modification regulates stochastic expression of clustered protocadherin genes, generating single neuron diversity.

In the brain, enormous numbers of neurons have functional individuality and distinct circuit specificities. Clustered Protocadherins (Pcdhs), diversified cell-surface proteins, are stochastically expressed by alternative promoter choice and affect dendritic arborization in individual neurons. Here we found that the Pcdh promoters are differentially methylated by the de novo DNA methyltransferase Dnmt3b during early embryogenesis.

NMDAR-regulated dynamics of layer 4 neuronal dendrites during thalamocortical reorganization in neonates.

Thalamocortical (TC) connectivity is reorganized by thalamic inputs during postnatal development; however, the dynamic characteristics of TC reorganization and the underlying mechanisms remain unexplored. We addressed this question using dendritic refinement of layer 4 (L4) stellate neurons in mouse barrel cortex (barrel cells) as a model; dendritic refinement of L4 neurons is a critical component of TC reorganization through which postsynaptic L4 neurons acquire their dendritic orientation toward presynaptic TC axon termini. Simultaneous labeling of TC axons and individual barrel cell dendrites allowed in vivo time-lapse imaging of dendritic refinement in the neonatal cortex.

Distinct cerebellar engrams in short-term and long-term motor learning.

Cerebellar motor learning is suggested to be caused by long-term plasticity of excitatory parallel fiber-Purkinje cell (PF-PC) synapses associated with changes in the number of synaptic AMPA-type glutamate receptors (AMPARs). However, whether the AMPARs decrease or increase in individual PF-PC synapses occurs in physiological motor learning and accounts for memory that lasts over days remains elusive. We combined quantitative SDS-digested freeze-fracture replica labeling for AMPAR and physical dissector electron microscopy with a simple model of cerebellar motor learning, adaptation of horizontal optokinetic response (HOKR) in mouse.

CTCF is required for neural development and stochastic expression of clustered Pcdh genes in neurons.

The CCCTC-binding factor (CTCF) is a key molecule for chromatin conformational changes that promote cellular diversity, but nothing is known about its role in neurons. Here, we produced mice with a conditional knockout (cKO) of CTCF in postmitotic projection neurons, mostly in the dorsal telencephalon. The CTCF-cKO mice exhibited postnatal growth retardation and abnormal behavior and had defects in functional somatosensory mapping in the brain.

Native GABA(B) receptors are heteromultimers with a family of auxiliary subunits.

GABA(B) receptors are the G-protein-coupled receptors for gamma-aminobutyric acid (GABA), the main inhibitory neurotransmitter in the brain. They are expressed in almost all neurons of the brain, where they regulate synaptic transmission and signal propagation by controlling the activity of voltage-gated calcium (Ca(v)) and inward-rectifier potassium (K(ir)) channels. Molecular cloning revealed that functional GABA(B) receptors are formed by the heteromeric assembly of GABA(B1) with GABA(B2) subunits.

Input-specific intrasynaptic arrangements of ionotropic glutamate receptors and their impact on postsynaptic responses.

To examine the intrasynaptic arrangement of postsynaptic receptors in relation to the functional role of the synapse, we quantitatively analyzed the two-dimensional distribution of AMPA and NMDA receptors (AMPARs and NMDARs, respectively) using SDS-digested freeze-fracture replica labeling (SDS-FRL) and assessed the implication of distribution differences on the postsynaptic responses by simulation. In the dorsal lateral geniculate nucleus, corticogeniculate (CG) synapses were twice as large as retinogeniculate (RG) synapses but expressed similar numbers of AMPARs. Two-dimensional views of replicas revealed that AMPARs form microclusters in both synapses to a similar extent, resulting in larger AMPAR-lacking areas in the CG synapses.

Dendritic Ih ensures high-fidelity dendritic spike responses of motion-sensitive neurons in rat superior colliculus.

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels that generate I(h) currents are widely distributed in the brain and have been shown to contribute to various neuronal functions. In the present study, we investigated the functions of I(h) in the motion-sensitive projection neurons [wide field vertical (WFV) cells] of the superior colliculus, a pivotal visual center for detection of and orientating to salient objects. Combination of whole cell recordings and immunohistochemical investigations suggested that HCN1 channels dominantly contribute to the I(h) in WFV cells among HCN isoforms expressed in the superficial superior colliculus and mainly located on their expansive dendritic trees.

Number and density of AMPA receptors in individual synapses in the rat cerebellum as revealed by SDS-digested freeze-fracture replica labeling.

The number of AMPA receptor (AMPAR) is the major determinant of synaptic strength at glutamatergic synapses, but little is known about the absolute number and density of AMPARs in individual synapses. Using SDS-digested freeze-fracture replica labeling, which has high detection efficiency comparable with electrophysiological noise analysis for functional AMPAR, we analyzed three kinds of excitatory synapses in the molecular layer of the adult rat cerebellum. In parallel fiber (PF)-Purkinje cell (PC) synapses, we found large variability in the number (38.

Number and density of AMPA receptors in single synapses in immature cerebellum.

The number of ionotropic receptors in synapses is an essential factor for determining the efficacy of fast transmission. We estimated the number of functional AMPA receptors at single postsynaptic sites by a combination of two-photon uncaging of glutamate and the nonstationary fluctuation analysis in immature rat Purkinje cells (PCs), which receive a single type of excitatory input from climbing fibers. Areas of postsynaptic membrane specialization at the recorded synapses were measured by reconstruction of serial ultrathin sections.