Lack of CaV3.1 channels causes severe motor coordination defects and an age-dependent cerebellar atrophy in a genetic model of essential tremor.

T-type Ca(2+) channels have been implicated in tremorogenesis and motor coordination. The α1 subunit of the Ca(V)3.1 T-type Ca(2+) channel is highly expressed in motor pathways in the brain, but knockout of the Ca(V)3.1 gene (α(1G)(-/-)) per se causes no motor defects in mice. Thus, the role of Ca(V)3.1 channels in motor control remains obscure in vivo. Here, we investigated the effect of the Ca(V)3.1 knockout in the null genetic background of α1 GABA(A) receptor (α1(-/-)) by generating the double mutants (α1(-/-)/α(1G)(-/-)). α1(-/-)/α(1G)(-/-) mice showed severer motor abnormalities than α1(-/-) mice as measured by potentiated tremor activities at 20Hz and impaired motor learning. Propranolol, an anti-ET drug that is known to reduce the pathologic tremor in α1(-/-) mice, was not effective for suppressing the potentiated tremor in α1(-/-)/α(1G)(-/-) mice. In addition, α1(-/-)/α(1G)(-/-) mice showed an age-dependent loss of cerebellar Purkinje neurons. These results suggest that α1(-/-)/α(1G)(-/-) mice are a novel mouse model for a distinct subtype of ET in human and that Ca(V)3.1 T-type Ca(2+) channels play a role in motor coordination under pathological conditions.

Diaminodiphenyl sulfone-induced parkin ameliorates age-dependent dopaminergic neuronal loss.

During normal aging, the number of dopaminergic (DA) neurons in the substantia nigra progressively diminishes, although massive DA neuronal loss is a hallmark sign of Parkinson's disease. Unfortunately, there is little known about the molecular events involved in age-related DA neuronal loss. In this study, we found that (1) the level of parkin was decreased in the cerebellum, brain stem, substantia nigra, and striatum of aged mice, (2) diaminodiphenyl sulfone (DDS) restored the level of parkin, (3) DDS prevented age-dependent DA neuronal loss, and (4) DDS protected SH-SY5Y cells from 1-methyl-4-phenylpyridinium and hydrogen peroxide. Furthermore, pretreatment and/or post-treatment of DDS in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinson's disease model attenuated DA neuronal loss and restored motor behavior. DDS transcriptionally activated parkin via protein kinase RNA-like endoplasmic reticulum kinase-activating transcription factor 4 signaling and DDS not only failed to induce parkin expression but also failed to rescue SH-SY5Y cells from 1-methyl-4-phenylpyridinium in the absence of ATF4. Herein, we demonstrated for the first time that DDS increased parkin level and served as a neuroprotective agent for age-dependent DA neuronal loss. Thus, DDS may be a potential therapeutic agent for age-related neurodegeneration.

Heterogeneity of tremor mechanisms assessed by tremor-related cortical potential in mice.

BACKGROUND: Identifying a neural circuit mechanism that is differentially involved in tremor would aid in the diagnosis and cure of such cases. Here, we demonstrate that tremor-related cortical potential (TRCP) is differentially expressed in two different mouse models of tremor. RESULTS: Hybrid tremor analysis of harmaline-induced and genetic tremor in mice revealed that two authentic tremor frequencies for each type of tremor were conserved and showed an opposite dependence on CaV3.1 T-type Ca(2+) channels. Electroencephalogram recordings revealed that α1(-/-);α1G(-/-) mice double-null for the GABA receptor α1 subunit (Gabra1) and CaV3.1 T-type Ca(2+) channels (Cacna1g), in which the tremor caused by the absence of Gabra1 is potentiated by the absence of Cacna1g, showed a coherent TRCP that exhibited an onset that preceded the initiation of behavioral tremor by 3 ms. However, harmaline-induced tremor, which is known to be abolished by α1G(-/-), showed no TRCP. CONCLUSIONS: Our results demonstrate that the α1(-/-);α1G(-/-) double-knockout tremor model is useful for studying cortical mechanisms of tremor.

Promotion of Remyelination by Sulfasalazine in a Transgenic Zebrafish Model of Demyelination.

Most of the axons in the vertebrate nervous system are surrounded by a lipid-rich membrane called myelin, which promotes rapid conduction of nerve impulses and protects the axon from being damaged. Multiple sclerosis (MS) is a chronic demyelinating disease of the CNS characterized by infiltration of immune cells and progressive damage to myelin and axons. One potential way to treat MS is to enhance the endogenous remyelination process, but at present there are no available treatments to promote remyelination in patients with demyelinating diseases. Sulfasalazine is an anti-inflammatory and immune-modulating drug that is used in rheumatology and inflammatory bowel disease. Its anti-inflammatory and immunomodulatory properties prompted us to test the ability of sulfasalazine to promote remyelination. In this study, we found that sulfasalazine promotes remyelination in the CNS of a transgenic zebrafish model of NTR/MTZ-induced demyelination. We also found that sulfasalazine treatment reduced the number of macrophages/microglia in the CNS of demyelinated zebrafish larvae, suggesting that the acceleration of remyelination is mediated by the immunomodulatory function of sulfasalazine. Our data suggest that temporal modulation of the immune response by sulfasalazine can be used to overcome MS by enhancing myelin repair and remyelination in the CNS.

Spatiotemporal control of fibroblast growth factor receptor signals by blue light.

Fibroblast growth factor receptors (FGFRs) regulate diverse cellular behaviors that should be exquisitely controlled in space and time. We engineered an optically controlled FGFR (optoFGFR1) by exploiting cryptochrome 2, which homointeracts upon blue light irradiation. OptoFGFR1 can rapidly and reversibly control intracellular FGFR1 signaling within seconds by illumination with blue light. At the subcellular level, localized activation of optoFGFR1 induced cytoskeletal reorganization. Utilizing the high spatiotemporal precision of optoFGFR1, we efficiently controlled cell polarity and induced directed cell migration. OptoFGFR1 provides an effective means to precisely control FGFR signaling and is an important optogenetic tool that can be used to study diverse biological processes both in vitro and in vivo.

Light-inducible receptor tyrosine kinases that regulate neurotrophin signalling.

Receptor tyrosine kinases (RTKs) are a family of cell-surface receptors that have a key role in regulating critical cellular processes. Here, to understand and precisely control RTK signalling, we report the development of a genetically encoded, photoactivatable Trk (tropomyosin-related kinase) family of RTKs using a light-responsive module based on Arabidopsis thaliana cryptochrome 2. Blue-light stimulation (488 nm) of mammalian cells harbouring these receptors robustly upregulates canonical Trk signalling. A single light stimulus triggers transient signalling activation, which is reversibly tuned by repetitive delivery of blue-light pulses. In addition, the light-provoked process is induced in a spatially restricted and cell-specific manner. A prolonged patterned illumination causes sustained activation of extracellular signal-regulated kinase and promotes neurite outgrowth in a neuronal cell line, and induces filopodia formation in rat hippocampal neurons. These light-controllable receptors are expected to create experimental opportunities to spatiotemporally manipulate many biological processes both in vitro and in vivo.

Small molecule-based reversible reprogramming of cellular lifespan.

Most somatic cells encounter an inevitable destiny, senescence. Little progress has been made in identifying small molecules that extend the finite lifespan of normal human cells. Here we show that the intrinsic 'senescence clock' can be reset in a reversible manner by selective modulation of the ataxia telangiectasia-mutated (ATM) protein and ATM- and Rad3-related (ATR) protein with a small molecule, CGK733. This compound was identified by a high-throughput phenotypic screen with automated imaging. Employing a magnetic nanoprobe technology, magnetism-based interaction capture (MAGIC), we identified ATM as the molecular target of CGK733 from a genome-wide screen. CGK733 inhibits ATM and ATR kinase activities and blocks their checkpoint signaling pathways with great selectivity. Consistently, siRNA-mediated knockdown of ATM and ATR induced the proliferation of senescent cells, although with lesser efficiency than CGK733. These results might reflect the specific targeting of the kinase activities of ATM and ATR by CGK733 without affecting any other domains required for cell proliferation.