Casein kinase I epsilon gene transfer into the suprachiasmatic nucleus via electroporation lengthens circadian periods of tau mutant hamsters

Gene Electrotransfer via Conductivity-Clamped Electric Field Focusing Pivots Sensori-Motor DNA Therapeutics: "A Spoonful of Sugar Helps the Medicine Go Down"

Viral vectors and lipofection-based gene therapies have dispersion-dependent transduction/transfection profiles that thwart precise targeting. The study describes the development of focused close-field gene electrotransfer (GET) technology, refining spatial control of gene expression. Integration of fluidics for precise delivery of "naked" plasmid deoxyribonucleic acid (DNA) in sucrose carrier within the focused electric field enables negative biasing of near-field conductivity ("conductivity-clamping"-CC), increasing the efficiency of plasma membrane molecular translocation. This enables titratable gene delivery with unprecedently low charge transfer. The clinic-ready bionics-derived CC-GET device achieved neurotrophin-encoding miniplasmid DNA delivery to the cochlea to promote auditory nerve regeneration; validated in deafened guinea pig and cat models, leading to improved central auditory tuning with bionics-based hearing. The performance of CC-GET is evaluated in the brain, an organ problematic for pulsed electric field-based plasmid DNA delivery, due to high required currents causing Joule-heating and damaging electroporation. Here CC-GET enables safe precision targeting of gene expression. In the guinea pig, reporter expression is enabled in physiologically critical brainstem regions, and in the striatum (globus pallidus region) delivery of a red-shifted channelrhodopsin and a genetically-encoded Ca2+ sensor, achieved photoactivated neuromodulation relevant to the treatment of Parkinson's Disease and other focal brain disorders.

A Critical Review of Electroporation as A Plasmid Delivery System in Mouse Skeletal Muscle

The gene delivery to skeletal muscles is a promising strategy for the treatment of both muscular disorders (by silencing or overexpression of specific gene) and systemic secretion of therapeutic proteins. The use of a physical method like electroporation with plate or needle electrodes facilitates long-lasting gene silencing in situ. It has been reported that electroporation enhances the expression of the naked DNA gene in the skeletal muscle up to 100 times and decreases the changeability of the intramuscular expression. Coelectransfer of reporter genes such as green fluorescent protein (GFP), luciferase or beta-galactosidase allows the observation of correctly performed silencing in the muscles. Appropriate selection of plasmid injection volume and concentration, as well as electrotransfer parameters, such as the voltage, the length and the number of electrical pulses do not cause long-term damage to myocytes. In this review, we summarized the electroporation methodology as well as the procedure of electrotransfer to the gastrocnemius, tibialis, soleus and foot muscles and compare their advantages and disadvantages.

NPAS2 Regulation of Anxiety-Like Behavior and GABAA Receptors

Abnormal circadian rhythms and circadian genes are strongly associated with several psychiatric disorders. Neuronal PAS Domain Protein 2 (NPAS2) is a core component of the molecular clock that acts as a transcription factor and is highly expressed in reward- and stress-related brain regions such as the striatum. However, the mechanism by which NPAS2 is involved in mood-related behaviors is still unclear. We measured anxiety-like behaviors in mice with a global null mutation in Npas2 (Npas2 null mutant mice) and found that Npas2 null mutant mice exhibit less anxiety-like behavior than their wild-type (WT) littermates (in elevated plus maze, light/dark box and open field assay). We assessed the effects of acute or chronic stress on striatal Npas2 expression, and found that both stressors increased levels of Npas2. Moreover, knockdown of Npas2 in the ventral striatum resulted in a similar reduction of anxiety-like behaviors as seen in the Npas2 null mutant mouse. Additionally, we identified Gabra genes as transcriptional targets of NPAS2, found that Npas2 null mutant mice exhibit reduced sensitivity to the GABAa positive allosteric modulator, diazepam and that knockdown of Npas2 reduced Gabra1 expression and response to diazepam in the ventral striatum. These results: (1) implicate Npas2 in the response to stress and the development of anxiety; and (2) provide functional evidence for the regulation of GABAergic neurotransmission by NPAS2 in the ventral striatum.

Low Current-driven Micro-electroporation Allows Efficient In Vivo Delivery of Nonviral DNA into the Adult Mouse Brain

Viral gene transfer or transgenic animals are commonly used technologies to alter gene expression in the adult brain, although these approaches lack spatial specificity and are time consuming. We delivered plasmid DNA locally into the brain of adult C57BL/6 mice in vivo by voltage- and current-controlled electroporation. The low current-controlled delivery of unipolar square wave pulses of 125 µA with microstimulation electrodes at the injection site gave 16 times higher transfection rates than a voltage-controlled electroporation protocol with plate electrodes resulting in currents of about 400 mA. Transfection was restricted to the target region and no damage due to the electric pulses was found. Our current-controlled electroporation protocol indicated that the use of very low currents resulting in applied voltages within the physiological range of the membrane potential, allows efficient transfection of nonviral plasmid DNA. In conclusion, low current-controlled electroporation is an excellent approach for electroporation in the adult brain, i.e., gene function can be influenced locally at a high level with no mortality and minimal tissue damage.

Endogenous casein kinase-1 modulates NMDA receptor activity of hypothalamic presympathetic neurons and sympathetic outflow in hypertension

KEY POINTS

Increased NMDA receptor activity and excitability of presympathetic neurons in the hypothalamus can increase sympathetic nerve discharges leading to hypertension. In this study, we determined how protein kinases and phosphatases are involved in regulating NMDA receptor activity and firing activity of presympathetic neurons in the hypothalamus in normotensive and hypertensive rats. We show that casein kinase-1 inhibition increases NMDA receptor activity and excitability of presympathetic neurons in the hypothalamus and augments sympathetic nerve discharges in normotensive, but not in hypertensive, rats. Our data indicate that casein kinase-1 tonically regulates NMDA receptor activity by interacting with casein kinase-2 and protein phosphatases in the hypothalamus and that imbalance of NMDA receptor phosphorylation can augment the excitability of hypothalamic presympathetic neurons and sympathetic nerve discharges in hypertension. These findings help us understand the neuronal mechanism of hypertension, and reducing the NMDA receptor phosphorylation level may be effective for treating neurogenic hypertension.

ABSTRACT

Increased N-methyl-d-aspartate receptor (NMDAR) activity in the paraventricular nucleus (PVN) of the hypothalamus is involved in elevated sympathetic outflow in hypertension. However, the molecular mechanisms underlying augmented NMDAR activity in hypertension remain unclear. In this study, we determined the role of casein kinase-1 (CK1) in regulating NMDAR activity in the PVN. NMDAR-mediated excitatory postsynaptic currents (EPSCs) and puff NMDA-elicited currents were recorded in spinally projecting PVN neurons in spontaneously hypertensive rats (SHRs) and Wistar-Kyoto (WKY) rats. The basal amplitudes of evoked NMDAR-EPSCs and puff NMDA currents were significantly higher in SHRs than in WKY rats. The CK1 inhibitor PF4800567 or PF670462 significantly increased the amplitude of NMDAR-EPSCs and puff NMDA currents in PVN neurons in WKY rats but not in SHRs. PF4800567 caused an NMDAR-dependent increase in the excitability of PVN neurons only in WKY rats. Also, the CK1ε protein level in the PVN was significantly lower in SHRs than in WKY rats. Furthermore, intracerebroventricular infusion of PF4800567 increased blood pressure and lumbar sympathetic nerve activity in WKY rats, and this effect was eliminated by microinjection of the NMDAR antagonist into the PVN. In addition, PF4800567 failed to increase NMDAR activity in brain slices of WKY rats pretreated with the protein phosphatase 1/2A, calcineurin, or casein kinase-2 inhibitor. Our findings suggest that CK1 tonically suppresses NMDAR activity in the PVN by reducing the NMDAR phosphorylation level. Diminished CK1 activity may contribute to potentiated glutamatergic synaptic input to PVN presympathetic neurons and elevated sympathetic vasomotor tone in neurogenic hypertension.

Circadian rhythms and addiction: mechanistic insights and future directions

Circadian rhythms are prominent in many physiological and behavioral functions. Circadian disruptions either by environmental or molecular perturbation can have profound health consequences, including the development and progression of addiction. Both animal and humans studies indicate extensive bidirectional relationships between the circadian system and drugs of abuse. Addicted individuals display disrupted rhythms, and chronic disruption or particular chronotypes may increase the risk for substance abuse and relapse. Moreover, polymorphisms in circadian genes and an evening chronotype have been linked to mood and addiction disorders, and recent efforts suggest an association with the function of reward neurocircuitry. Animal studies are beginning to determine how altered circadian gene function results in drug-induced neuroplasticity and behaviors. Many studies suggest a critical role for circadian rhythms in reward-related pathways in the brain and indicate that drugs of abuse directly affect the central circadian pacemaker. In this review, we highlight key findings demonstrating the importance of circadian rhythms in addiction and how future studies will reveal important mechanistic insights into the involvement of circadian rhythms in drug addiction.

Delivery of DNA into the central nervous system via electroporation

Electroporation of non-viral plasmid DNA is a valuable tool to alter gene expression in the adult central nervous system. It offers a number of advantages over viral gene delivery as non-viral plasmids can integrate larger inserts and reduce the risk of inducing unintended immunological responses. Generally, electroporation of the adult brain is accomplished in rodents by applying high-amplitude voltage-controlled pulses through the entire brain with plate electrodes surrounding the animal's head. Here, we describe an alternative electroporation protocol making use of current-controlled low-amplitude pulses that are delivered locally by means of needlelike electrodes in the brain of adult mice. This allows altering gene expression in very-well-defined areas of the brain while inducing minimal tissue damage.

shRNA-mediated gene knockdown in skeletal muscle

RNA interference appears as a promising tool for therapeutic gene silencing to block protein expression. A long-lived silencing is obtained through the in situ expression of shRNA. A safe approach is to use a physical method such as in vivo electropulsation with plate electrodes. This is presently validated in muscles by the in vivo coelectrotransfer of plasmids specifically coding for expression and silencing of a fluorescent protein. No long-lived tissue damage is observed by the proper choice of the electric pulsing parameters and the amount of injected plasmids. Using a noninvasive fluorescence imaging assay, electrodelivery in mouse muscles is observed to induce complete silencing over more than 2 months in a specific way. The proper choices of the plasmids (sequence, promoter, and relative amounts) appear as key parameters in the successful long-term silencing.

In vivo electroporation of the central nervous system: a non-viral approach for targeted gene delivery

Electroporation is a widely used technique for enhancing the efficiency of DNA delivery into cells. Application of electric pulses after local injection of DNA temporarily opens cell membranes and facilitates DNA uptake. Delivery of plasmid DNA by electroporation to alter gene expression in tissue has also been explored in vivo. This approach may constitute an alternative to viral gene transfer, or to transgenic or knock-out animals. Among the most frequently electroporated target tissues are skin, muscle, eye, and tumors. Moreover, different regions in the central nervous system (CNS), including the developing neural tube and the spinal cord, as well as prenatal and postnatal brain have been successfully electroporated. Here, we present a comprehensive review of the literature describing electroporation of the CNS with a focus on the adult brain. In addition, the mechanism of electroporation, different ways of delivering the electric pulses, and the risk of damaging the target tissue are highlighted. Electroporation has been successfully used in humans to enhance gene transfer in vaccination or cancer therapy with several clinical trials currently ongoing. Improving the knowledge about in vivo electroporation will pave the way for electroporation-enhanced gene therapy to treat brain carcinomas, as well as CNS disorders such as Alzheimer's disease, Parkinson's disease, and depression.

Physiology of circadian entrainment

Mammalian circadian rhythms are controlled by endogenous biological oscillators, including a master clock located in the hypothalamic suprachiasmatic nuclei (SCN). Since the period of this oscillation is of approximately 24 h, to keep synchrony with the environment, circadian rhythms need to be entrained daily by means of Zeitgeber ("time giver") signals, such as the light-dark cycle. Recent advances in the neurophysiology and molecular biology of circadian rhythmicity allow a better understanding of synchronization. In this review we cover several aspects of the mechanisms for photic entrainment of mammalian circadian rhythms, including retinal sensitivity to light by means of novel photopigments as well as circadian variations in the retina that contribute to the regulation of retinal physiology. Downstream from the retina, we examine retinohypothalamic communication through neurotransmitter (glutamate, aspartate, pituitary adenylate cyclase-activating polypeptide) interaction with SCN receptors and the resulting signal transduction pathways in suprachiasmatic neurons, as well as putative neuron-glia interactions. Finally, we describe and analyze clock gene expression and its importance in entrainment mechanisms, as well as circadian disorders or retinal diseases related to entrainment deficits, including experimental and clinical treatments.

Aging in the circadian system: considerations for health, disease prevention and longevity

The circadian system orchestrates internal physiology on a daily schedule to promote optimal health and maximize disease prevention. Chronic disruptions in circadian function are associated with an increase in a variety of disease states including, heart disease, ulcers and diabetes. With advanced age, the genes regulating circadian function at the cellular level become disorganized and the ability of the brain clock to entrain to local time diminishes. As a result, aged individuals exhibit a loss of temporal coordination among bodily systems, leading to deficits in homeostasis and sub-optimal functioning. Such disruptions in the circadian system appear to accelerate the aging process and contribute to senescence, with some systems being more vulnerable than others. This review explores aging-associated changes in circadian function and examines evidence linking such alterations to adverse health consequences in late life and promotion of the aging process.

Long-lasting In vivo Gene Silencing by Electrotransfer of shRNA Expressing Plasmid

RNA interference appears as a promising tool for therapeutic gene silencing. A key limit is the delivery of the siRNA. A safe approach is to use a physical method such as in vivo electropulsation with contact electrodes. Getting a long lived silencing can be better approached by using the in situ expression of shRNA. This is presently obtained by using co-electrotransfer of specific plasmids coding for expression and silencing of a fluorescent protein. Using a non invasive fluorescence imaging assay, electrodelivery in mouse muscles is observed to induce complete silencing over more than two months in a specific way. The proper choices of the plasmids (sequence and relative amounts) and of the electric pulsing conditions appear as key parameters in the successful silencing.