Heterogeneous side effects of cortical inactivation in behaving animals.

Cortical inactivation represents a key causal manipulation allowing the study of cortical circuits and their impact on behavior. A key assumption in inactivation studies is that the neurons in the target area become silent while the surrounding cortical tissue is only negligibly impacted. However, individual neurons are embedded in complex local circuits composed of excitatory and inhibitory cells with connections extending hundreds of microns.

Pathogenic STX3 variants affecting the retinal and intestinal transcripts cause an early-onset severe retinal dystrophy in microvillus inclusion disease subjects.

Biallelic STX3 variants were previously reported in five individuals with the severe congenital enteropathy, microvillus inclusion disease (MVID). Here, we provide a significant extension of the phenotypic spectrum caused by STX3 variants. We report ten individuals of diverse geographic origin with biallelic STX3 loss-of-function variants, identified through exome sequencing, single-nucleotide polymorphism array-based homozygosity mapping, and international collaboration.

The SNARE regulator Complexin3 is a target of the cone circadian clock.

BMAL1 is a core component of the mammalian circadian clockwork. Removal of BMAL1 from the retina significantly affects visual information processing in both rod and cone pathways. To identify potential pathways and/or molecules through which BMAL1 alters signal transmission at the cone pedicle, we performed an RNA-seq differential expression analysis between cone-specific Bmal1 knockout cones (cone-Bmal1 ) and wild-type (WT) cones.

Simultaneous Release of Multiple Vesicles from Rods Involves Synaptic Ribbons and Syntaxin 3B.

First proposed as a specialized mode of release at sensory neurons possessing ribbon synapses, multivesicular release has since been described throughout the central nervous system. Many aspects of multivesicular release remain poorly understood. We explored mechanisms underlying simultaneous multivesicular release at ribbon synapses in salamander retinal rod photoreceptors.

Integration of cortical population signals for visual perception.

Visual stimuli evoke heterogeneous responses across nearby neural populations. These signals must be locally integrated to contribute to perception, but the principles underlying this process are unknown. Here, we exploit the systematic organization of orientation preference in macaque primary visual cortex (V1) and perform causal manipulations to examine the limits of signal integration.

Extending the Time Domain of Neuronal Silencing with Cryptophyte Anion Channelrhodopsins.

Optogenetic inhibition of specific neuronal types in the brain enables analysis of neural circuitry and is promising for the treatment of a number of neurological disorders. Anion channelrhodopsins (ACRs) from the cryptophyte alga generate larger photocurrents than other available inhibitory optogenetic tools, but more rapid channels are needed for temporally precise inhibition, such as single-spike suppression, of high-frequency firing neurons. Faster ACRs have been reported, but their potential advantages for time-resolved inhibitory optogenetics have not so far been verified in neurons.

Two Pools of Vesicles Associated with Synaptic Ribbons Are Molecularly Prepared for Release.

Neurons that form ribbon-style synapses are specialized for continuous exocytosis. To this end, their synaptic terminals contain numerous synaptic vesicles, some of which are ribbon associated, that have difference susceptibilities for undergoing Ca-dependent exocytosis. In this study, we probed the relationship between previously defined vesicle populations and determined their fusion competency with respect to SNARE complex formation.

The Expanding Family of Natural Anion Channelrhodopsins Reveals Large Variations in Kinetics, Conductance, and Spectral Sensitivity.

Natural anion channelrhodopsins (ACRs) discovered in the cryptophyte alga Guillardia theta generate large hyperpolarizing currents at membrane potentials above the Nernst equilibrium potential for Cl and thus can be used as efficient inhibitory tools for optogenetics. We have identified and characterized new ACR homologs in different cryptophyte species, showing that all of them are anion-selective, and thus expanded this protein family to 20 functionally confirmed members. Sequence comparison of natural ACRs and engineered Cl-conducting mutants of cation channelrhodopsins (CCRs) showed radical differences in their anion selectivity filters.

NEUROSCIENCE. Natural light-gated anion channels: A family of microbial rhodopsins for advanced optogenetics.

Light-gated rhodopsin cation channels from chlorophyte algae have transformed neuroscience research through their use as membrane-depolarizing optogenetic tools for targeted photoactivation of neuron firing. Photosuppression of neuronal action potentials has been limited by the lack of equally efficient tools for membrane hyperpolarization. We describe anion channel rhodopsins (ACRs), a family of light-gated anion channels from cryptophyte algae that provide highly sensitive and efficient membrane hyperpolarization and neuronal silencing through light-gated chloride conduction.

Phosphorylation of syntaxin 3B by CaMKII regulates the formation of t-SNARE complexes.

Ribbon synapses in the retina lack the t-SNARE (target-soluble N-ethylmaleimide-sensitive factor attachment protein receptor) syntaxin 1A that is found in conventional synapses of the nervous system, but instead contain the related isoform syntaxin 3B. Previous studies have demonstrated that syntaxin 3B is essential for synaptic vesicle exocytosis in ribbon synapses, but syntaxin 3B is less efficient than syntaxin 1A in binding the t-SNARE protein SNAP-25 and catalyzing vesicle fusion. We demonstrate here that syntaxin 3B is localized mainly on the presynaptic membrane of retinal ribbon synapses and that a subset of syntaxin 3B is localized in close proximity to the synaptic ribbon.

Characterization of a highly efficient blue-shifted channelrhodopsin from the marine alga Platymonas subcordiformis.

Rhodopsin photosensors of phototactic algae act as light-gated cation channels when expressed in animal cells. These proteins (channelrhodopsins) are extensively used for millisecond scale photocontrol of cellular functions (optogenetics). We report characterization of PsChR, one of the phototaxis receptors in the alga Platymonas (Tetraselmis) subcordiformis.

SV2 acts via presynaptic calcium to regulate neurotransmitter release.

Synaptic vesicle 2 (SV2) proteins, critical for proper nervous system function, are implicated in human epilepsy, yet little is known about their function. We demonstrate, using direct approaches, that loss of the major SV2 isoform in a central nervous system nerve terminal is associated with an elevation in both resting and evoked presynaptic Ca(2+) signals. This increase is essential for the expression of the SV2B(-/-) secretory phenotype, characterized by changes in synaptic vesicle dynamics, synaptic plasticity, and synaptic strength.

Physical and functional interaction between the dopamine transporter and the synaptic vesicle protein synaptogyrin-3.

Uptake through the dopamine transporter (DAT) represents the primary mechanism used to terminate dopaminergic transmission in brain. Although it is well known that dopamine (DA) taken up by the transporter is used to replenish synaptic vesicle stores for subsequent release, the molecular details of this mechanism are not completely understood. Here, we identified the synaptic vesicle protein synaptogyrin-3 as a DAT interacting protein using the split ubiquitin system.

Glycosylated SV2A and SV2B mediate the entry of botulinum neurotoxin E into neurons.

Botulinum neurotoxin E (BoNT/E) can cause paralysis in humans and animals by blocking neurotransmitter release from presynaptic nerve terminals. How this toxin targets and enters neurons is not known. Here we identified two isoforms of the synaptic vesicle protein SV2, SV2A and SV2B, as the protein receptors for BoNT/E.

Syntaxin 3b is a t-SNARE specific for ribbon synapses of the retina.

Previous studies have demonstrated that ribbon synapses in the retina do not contain the t-SNARE (target-soluble N-ethylmaleimide-sensitive factor attachment protein receptor) syntaxin 1A that is found in conventional synapses of the nervous system. In contrast, ribbon synapses of the retina contain the related isoform syntaxin 3. In addition to its localization in ribbon synapses, syntaxin 3 is also found in nonneuronal cells, where it has been implicated in the trafficking of transport vesicles to the apical plasma membrane of polarized cells.

SV2 is the protein receptor for botulinum neurotoxin A.

How the widely used botulinum neurotoxin A (BoNT/A) recognizes and enters neurons is poorly understood. We found that BoNT/A enters neurons by binding to the synaptic vesicle protein SV2 (isoforms A, B, and C). Fragments of SV2 that harbor the toxin interaction domain inhibited BoNT/A from binding to neurons.

Role of efficient neurotransmitter release in barrel map development.

Cortical maps are remarkably precise, with organized arrays of thalamocortical afferents (TCAs) that project into distinct neuronal modules. Here, we present evidence for the involvement of efficient neurotransmitter release in mouse cortical barrel map development using barrelless mice, a loss-of-function mutant of calcium/calmodulin-activated adenylyl cyclase I (AC1), and mice with a mutation in Rab3-interacting molecule 1alpha (RIM1alpha), an active zone protein that regulates neurotransmitter release. We demonstrate that release efficacy is substantially decreased in barrelless TCAs.

SV2A and SV2C are not vesicular Ca2+ transporters but control glucose-evoked granule recruitment.

Synaptic vesicle protein 2 (SV2) is expressed in neuroendocrine cells as three homologous isoforms, SV2A, SV2B and SV2C. Ca2+-dependent function in exocytosis has been attributed to SV2A and SV2B, without elucidation of the mechanism. The role of SV2C has not yet been addressed.

Genetic evidence for a protein-kinase-A-mediated presynaptic component in NMDA-receptor-dependent forms of long-term synaptic potentiation.

The synaptic vesicle protein Rab3A is a small GTP-binding protein that interacts with rabphilin and RIM1alpha, two presynaptic substrates of protein kinase A (PKA). Mice lacking RIM1alpha and Rab3A have a defect in PKA-dependent and NMDA receptor (NMDAR)-independent presynaptic long-term potentiation (LTP) at hippocampal mossy-fiber and cerebellar parallel-fiber synapses. In contrast, the NMDAR-dependent and PKA-independent early phase of LTP at hippocampal CA3-CA1 synapses does not require these presynaptic proteins.

SV2B regulates synaptotagmin 1 by direct interaction.

SV2 proteins are abundant synaptic vesicle proteins expressed in two major (SV2A and SV2B) and one minor (SV2C) isoform. SV2A and SV2B have been shown to be involved in the regulation of synaptic vesicle exocytosis. Previous studies found that SV2A, but not SV2B, can interact with the cytoplasmic domain of synaptotagmin 1, a Ca2+ sensor for synaptic vesicle exocytosis.

Characterization of synaptogyrin 3 as a new synaptic vesicle protein.

Synaptogyrins comprise a family of tyrosine-phosphorylated proteins with two neuronal (synaptogyrins 1 and 3) and one ubiquitous (cellugyrin) isoform. Previous studies have indicated that synaptogyrins are involved in the regulation of neurotransmitter release. Synaptogyrin 1 is a synaptic vesicle protein; cellugyrin, by contrast, is absent from synaptic vesicles.

Adenylyl cyclase I regulates AMPA receptor trafficking during mouse cortical 'barrel' map development.

Cortical map formation requires the accurate targeting, synaptogenesis, elaboration and refinement of thalamocortical afferents. Here we demonstrate the role of Ca2+/calmodulin-activated type-I adenylyl cyclase (AC1) in regulating the strength of thalamocortical synapses through modulation of AMPA receptor (AMPAR) trafficking using barrelless mice, a mutant without AC1 activity or cortical 'barrel' maps. Barrelless synapses are stuck in an immature state that contains few functional AMPARs that are rarely silent (NMDAR-only).

Differential distribution and developmental expression of synaptic vesicle protein 2 isoforms in the mouse retina.

Synaptic vesicle protein 2 (SV2), a ubiquitous synaptic vesicle protein, is known to participate in the regulation of Ca(2+)-mediated synaptic transmission, although its precise function has not been established. Three SV2 isoforms (SV2A, SV2B, SV2C) have been identified recently, each of which has a unique distribution in brain, suggesting synapse-specific functions. To determine if SV2A, -B, and -C are differentially distributed among synapses in the retina and the sequence of their development, we examined their distribution and expression patterns immunocytochemically in adult and developing mouse retina.