Journal of neurogenetics最新文献

The Drosophila light-activated Transient Receptor Potential (TRP) channel is the founding member of a large and diverse family of channel proteins. The Drosophila TRP (dTRP) channel, which generates the electrical response to light has been investigated in a great detail two decades before the first mammalian TRP channel was discovered. Thus, dTRP is unique among members of the TRP channel superfamily because its physiological role and the enzymatic cascade underlying its activation are established. In this article we outline the research leading to elucidation of dTRP as the light activated channel and focus on a major physiological property of the dTRP channel, which is indirect activation via a cascade of enzymatic reactions. These detailed pioneering studies, based on the genetic dissection approach, revealed that light activation of the Drosophila TRP channel is mediated by G-Protein-Coupled Receptor (GPCR)-dependent enzymatic cascade, in which phospholipase C β (PLC) is a crucial component. This physiological mechanism of Drosophila TRP channel activation was later found in mammalian TRPC channels. However, the initial studies on the mammalian TRPV1 channel indicated that it is activated directly by capsaicin, low pH and hot temperature (>42 °C). This mechanism of activation was apparently at odds with the activation mechanism of the TRPC channels in general and the Drosophila light activated TRP/TRPL channels in particular, which are target of a GPCR-activated PLC cascade. Subsequent studies have indicated that under physiological conditions TRPV1 is also target of a GPCR-activated PLC cascade in the generation of inflammatory pain. The Drosophila light-activated TRP channel is still a useful experimental paradigm because its physiological function as the light-activated channel is known, powerful genetic techniques can be applied to its further analysis, and signaling molecules involved in the activation of these channels are available.

The force-from-lipid (FFL) principle states that it is the lateral stretch force from the lipid membrane that ultimately opens mechanosensitive (MS) channels, not the external tether nor the internal cytoskeleton. Piezo channels for certain touch or proprioception and the hair-cell channels for hearing or balance apparently obey this principle, which is based on the idea that the lipid bilayer is an amphipathic compartment with a distinct internal force-distribution profile. Physical stretch or insertion of chemical impurities alters this profile, driving channel shape change to conform to the new environment. Thus, FFL governs all dynamic proteins embedded in membrane, including Kv's and TRPs. This article retraces the humble origin of the FFL concept. Paramecium research first created the mind set and the resources to electrically explore other microbial membranes. Patch clamp revealed MS-channel activities from yeast and E. coli spheroplasts. Despite formidable obstacles against interdisciplinary research, the E. coli MS-channel protein, MscL, was purified through fractionation by following its activity, much like enzyme purification. Reconstituted into a simple lipid bilayer, pure MscL retains mechanosensitivity, thus firmly establishing the FFL principle in 1994. The relatively simple MscL and its functional cousin MscS soon became ideal models for detailed analyses. Like the DNA-RNA-protein 'central dogma' or ATP synthesis, FFL is a fundamental principle, which appeared early in evolution, retained in all cellular life forms, and is expected to contribute to future molecular research on sensations, homeostasis, and embryonic development.

Previous studies have demonstrated the striking mutational effects of the Drosophila planar cell polarity gene prickle (pk) on larval motor axon microtubule-mediated vesicular transport and on adult epileptic behavior associated with neuronal circuit hyperexcitability. Mutant alleles of the prickle-prickle (pk^pk) and prickle-spiny-legs (pk^sple) isoforms (hereafter referred to as pk and sple alleles, respectively) exhibit differential phenotypes. While both pk and sple affect larval motor axon transport, only sple confers motor circuit and behavior hyperexcitability. However, mutations in the two isoforms apparently counteract to ameliorate adult motor circuit and behavioral hyperexcitability in heteroallelic pk^pk/pk^sple flies. We have further investigated the consequences of altered axonal transport in the development and function of the larval neuromuscular junction (NMJ). We uncovered robust dominant phenotypes in both pk and sple alleles, including synaptic terminal overgrowth (as revealed by anti-HRP and -Dlg immunostaining) and poor vesicle release synchronicity (as indicated by synaptic bouton focal recording). However, we observed recessive alteration of synaptic transmission only in pk/pk larvae, i.e. increased excitatory junctional potential (EJP) amplitude in pk/pk but not in pk/+ or sple/sple. Interestingly, for motor terminal excitability sustained by presynaptic Ca²⁺ channels, both pk and sple exerted strong effects to produce prolonged depolarization. Notably, only sple acted dominantly whereas pk/+ appeared normal, but was able to suppress the sple phenotypes, i.e. pk/sple appeared normal. Our observations contrast the differential roles of the pk and sple isoforms and highlight their distinct, variable phenotypic expression in the various structural and functional aspects of the larval NMJ.

Lesch-Nyhan disease (LND) is a neurodevelopmental disorder caused by variants in the HPRT1 gene, which encodes the enzyme hypoxanthine-guanine phosphoribosyl transferase (HGprt). HGprt deficiency provokes numerous metabolic changes which vary among different cell types, making it unclear which changes are most relevant for abnormal neural development. To begin to elucidate the consequences of HGprt deficiency for developing human neurons, neural stem cells (NSCs) were prepared from 6 induced pluripotent stem cell (iPSC) lines from individuals with LND and compared to 6 normal healthy controls. For all 12 lines, gene expression profiles were determined by RNA-seq and protein expression profiles were determined by shotgun proteomics. The LND lines revealed significant changes in expression of multiple genes and proteins. There was little overlap in findings between iPSCs and NSCs, confirming the impact of HGprt deficiency depends on cell type. For NSCs, gene expression studies pointed towards abnormalities in WNT signaling, which is known to play a role in neural development. Protein expression studies pointed to abnormalities in the mitochondrial F₀F₁ ATPase, which plays a role in maintaining cellular energy. These studies point to some mechanisms that may be responsible for abnormal neural development in LND.

Alzheimer's disease (AD) is the leading cause of dementia globally, but effective treatment is lacking. We aimed to explore lncRNA XIST role in AD and the mechanisms involved in the effect of changes in lncRNA XIST on the expression of Aβ-degrading enzymes. The mouse model of AD and the cell model induced by Aβ were established. LncRNA XIST, IDE, NEP, Plasmin, ACE, EZH2 expressions and distribution of XIST in the nucleus and cytoplasm were detected by qRT-PCR. Inflammatory cytokines IL-6, IL-1β, TNFα, IL-8, and Aβ42 levels were detected by ELISA. TUNEL was used to measure brain tissue damage. Cell proliferation was detected by CCK-8 assay. Flow cytometry detected cell apoptosis. RIP validated the combination of XIST and EZH2. ChIP verified that XIST recruits EZH2 to mediate enrichment of HEK27me3 in the NEP promoter region. The protein expression in brain tissues and cells was detected by Western blot. The expression of lncRNA XIST was increased in AD mice and cell models. Inflammation and injury of nerve cells occurred in AD mice and cell models. The knockdown of lncRNA XIST alleviated Aβ-induced neuronal inflammation and damage. LncRNA XIST affected the expression of Aβ-degrading enzyme NEP, and lncRNA XIST was negatively correlated with NEP expression in AD mice. LncRNA XIST regulated NEP expression partly through epigenetic regulation by binding with EZH2. LncRNA XIST mediated neuronal inflammation and injury through epigenetic regulation of NEP. Overall, our study found that lncRNA XIST induced Aβ accumulation and neuroinflammation by the epigenetic repression of NEP in AD.

Hypersynchronous neural activity is a characteristic feature of seizures. Although many Drosophila mutants of epilepsy-related genes display clear behavioral spasms and motor unit hyperexcitability, field potential measurements of aberrant hypersynchronous activity across brain regions during seizures have yet to be described. Here, we report a straightforward method to observe local field potentials (LFPs) from the Drosophila brain to monitor ensemble neural activity during seizures in behaving tethered flies. High frequency stimulation across the brain reliably triggers a stereotypic sequence of electroconvulsive seizure (ECS) spike discharges readily detectable in the dorsal longitudinal muscle (DLM) and coupled with behavioral spasms. During seizure episodes, the LFP signal displayed characteristic large-amplitude oscillations with a stereotypic temporal correlation to DLM flight muscle spiking. ECS-related LFP events were clearly distinct from rest- and flight-associated LFP patterns. We further characterized the LFP activity during different types of seizures originating from genetic and pharmacological manipulations. In the 'bang-sensitive' sodium channel mutant bangsenseless (bss), the LFP pattern was prolonged, and the temporal correlation between LFP oscillations and DLM discharges was altered. Following administration of the pro-convulsant GABA_A blocker picrotoxin, we uncovered a qualitatively different LFP activity pattern, which consisted of a slow (1-Hz), repetitive, waveform, closely coupled with DLM bursting and behavioral spasms. Our approach to record brain LFPs presents an initial framework for electrophysiological analysis of the complex brain-wide activity patterns in the large collection of Drosophila excitability mutants.