Biology subjects

Chow, C. H.

Publications and source records attributed to Chow, C. H..

5 recordsLinked to original sources

bioRxiv2023

SNAP-25, but not SNAP-23, is essential for photoreceptor function and survival in mice

Vesicular transport plays critical roles in photopigment delivery at photoreceptor outer segments and glutamate exocytosis at photoreceptor synapses. Previous studies into the role of photoreceptor SNAP proteins are limited in their characterizations into only gene/protein expression and do not delve further into their functional role. Here, we examine the expression and localization of SNAP-23 and SNAP-25 mRNA and protein. Using SNAP-23 and SNAP-25 conditional knockout mice, we further evaluated the morphological and functional consequences that the absence of these proteins has on vision. Although we found that the ubiquitously expressed SNAP-23 showed weak mRNA expression in photoreceptors, removal of SNAP-23 did not result in any observable phenotype. We found that neuronal SNAP-25 is developmentally regulated and SNAP-25 mRNA undergoes mRNA trafficking to the photoreceptor inner segments coinciding with the development of photoreceptor outer segments. Removal of SNAP-25 in photoreceptor cells led to changes in both outer segment protein trafficking and synaptic integrity, resulting in a complete loss of vision in SNAP-25 cKO mice. Our results conclude that SNAP-25, but not SNAP-23, is the essential isoform for photoreceptor survival and function.

neuroscience↗

bioRxiv2023

Mouse model of multiple sclerosis induced by disrupting vesicular transport in oligodendrocytes

Multiple Sclerosis is an autoimmune demyelination disorder with unknown etiology. Despite the myelin damage, the roles of myelinating oligodendrocytes in driving disease progression remain unknown. We hypothesize that disrupting vesicular transport in oligodendrocytes during adolescence will disrupt myelin integrity and causes neuroinflammation. By creating a mouse model of SNAP-23 conditional knockout in mature oligodendrocytes, we showed that impairment in vesicular trafficking in oligodendrocytes causes demyelination. Neuroinflammation with infiltration of peripheral immune T cells into the central nervous system was observed accompanied by demyelination. Mechanistically, SNAP-23 removal in oligodendrocytes caused abnormal axon-myelin structures and impaired myelin protein trafficking, both can contribute to autoimmune activation and demyelination. With our novel animal model, we propose that oligodendrocyte injury is an endogenous early event in triggering Multiple Sclerosis. One-Sentence SummaryImpaired vesicular transport in oligodendrocytes in adults caused demyelination and inflammation driving Multiple Sclerosis

neuroscience↗

bioRxiv2023

Differential Regulation of Excitatory vs Inhibitory Synaptic Release by Complexin/CPX-1 and CAPS/UNC-31 at the C. elegans Neuromuscular Junctions

The excitation and inhibition (E/I) balance at neuromuscular junctions plays a crucial role in coordinating animal motor behavior. Prominent synaptic vesicle secretory regulatory proteins, specifically complexin and CAPS (Calcium-dependent Activator Protein for Secretion), have not garnered sufficient attention for E/I balance regulation. Here, we investigate the roles of complexin/CPX-1 and CAPS/UNC-31 in excitatory vs inhibitory synapses of C. elegans neuromuscular junctions. In our study, cpx-1 null mutants displayed remarkable reduction evoked release in both excitatory and inhibitory synapses. Intriguingly, these mutants exhibited an enhanced level of spontaneous release, particularly within the context of excitatory synapse. This enhancement aligns with its "clamp" role that preventing SV from fusing with the presynaptic membrane. Additionally, a clamping-specific knockin mutant cpx-1({Delta}12), which displayed no alterations in evoked release at either type of synapse, also revealed a biased substantial increase in excitatory spontaneous release. In contrast, unc-31 null mutation, with normal spontaneous release, led to a more pronounced decreased evoked release in the excitatory synapse independent of dense-core vesicle regulation. Intriguingly, we found that the enhanced excitatory spontaneous release observed in cpx-1 mutants was abolished by unc-31 in a Ca2+-dependent manner, implying that UNC-31 is essential for maintaining a high level of spontaneous fusion events. Collectively, our findings unveil a distinct regulatory pattern governing excitatory and inhibitory synaptic release, orchestrated by the interplay of CPX-1 and UNC-31. Notably, we uncover an unforeseen role of UNC-31 in influencing CPX-1s "clamp" function, further adding complexity to the neural dynamics, which may underlie complex behavioral phenotypes observed in C. elegans.

neuroscience↗

bioRxiv2023

Double open syntaxin and UNC-18 P334A mutation leads to excitatory-inhibitory imbalance and impairs multiple aspects of C. elegans behavior

SNARE and Sec/Munc18 proteins are essential in synaptic vesicle exocytosis. Open form t-SNARE syntaxin and UNC-18 P334A are well-studied exocytosis-enhancing mutants. Here we investigate the interrelationship between the two mutations by generating double mutants in various genetic backgrounds in C. elegans. While each single mutation rescued the motility of CAPS/unc-31 and synaptotagmin/snt-1 mutants significantly, double mutations unexpectedly worsened motility or lost their rescuing effects. Electrophysiological analyses revealed that simultaneous mutations of open syntaxin and gain-of-function P334A UNC-18 induces a strong imbalance of excitatory over inhibitory transmission. In liposome fusion assays performed with mammalian proteins, the enhancement of fusion caused by the two mutations individually was abolished when the two mutations were introduced simultaneously, consistent with what we observed in C. elegans. We conclude that open syntaxin and P334A UNC-18 do not have additive beneficial effects, and this extends to C. elegans characteristics such as motility, growth, offspring bared, body size, and exocytosis, as well as liposome fusion in vitro. Our results also reveal unexpected differences between the regulation of exocytosis in excitatory versus inhibitory synapses.

neuroscience↗

bioRxiv2022

Neuronal SNAP-23 scales hippocampal synaptic plasticity and memory

Soluble NSF Attachment protein REceptor (SNARE)-mediated membrane fusion plays a crucial role not only in presynaptic vesicle exocytosis but also in postsynaptic receptor delivery. The latter is considered particularly important for long-term synaptic plasticity and learning and memory, yet underlying mechanisms including the identity of the key SNARE proteins remain elusive. Here, we investigate the role of neuronal Synaptosomal-Associated Protein-23 (SNAP-23) by analyzing pyramidal-neuron specific SNAP-23 conditional knockout (cKO) mice. SNAP-23 immunostaining in postsynaptic spines was effectively decreased in the SNAP-23 cKO hippocampus. Electrophysiological analysis of SNAP-23 deficient neurons using acute hippocampal slices showed normal basal neurotransmission in CA3-CA1 synapses with unchanged AMPA and NMDA currents. Nevertheless, we found theta-burst stimulation induced long-term potentiation (LTP) was vastly diminished in SNAP-23 cKO. Moreover, unlike syntaxin-4 cKO mice in which both basal neurotransmission and LTP decrease manifested changes in a broad set of behavioral tasks, deficits of SNAP-23 cKO is more limited to spatial memory. Our data reveal that neuronal SNAP-23 is selectively crucial for synaptic plasticity and spatial memory without affecting basal glutamate receptor function.

neuroscience↗