Thermogenetic stimulation of single neocortical pyramidal neurons transfected with TRPV1-L channels

Optogenetic and chemogenetic approaches for modeling neurological disorders in vivo

Animal models of human neurological disorders provide valuable experimental tools which enable us to study various aspects of disorder pathogeneses, ranging from structural abnormalities and disrupted metabolism and signaling to motor and mental deficits, and allow us to test novel therapies in preclinical studies. To be valid, these animal models should recapitulate complex pathological features at the molecular, cellular, tissue, and behavioral levels as closely as possible to those observed in human subjects. Pathological states resembling known human neurological disorders can be induced in animal species by toxins, genetic factors, lesioning, or exposure to extreme conditions. In recent years, novel animal models recapitulating neuropathologies in humans have been introduced. These animal models are based on synthetic biology approaches: opto- and chemogenetics. In this paper, we review recent opto- and chemogenetics-based animal models of human neurological disorders. These models allow for the creation of pathological states by disrupting specific processes at the cellular level. The artificial pathological states mimic a range of human neurological disorders, such as aging-related dementia, Alzheimer's and Parkinson's diseases, amyotrophic lateral sclerosis, epilepsy, and ataxias. Opto- and chemogenetics provide new opportunities unavailable with other animal models of human neurological disorders. These techniques enable researchers to induce neuropathological states varying in severity and ranging from acute to chronic. We also discuss future directions for the development and application of synthetic biology approaches for modeling neurological disorders.

Molecular Tools for Targeted Control of Nerve Cell Electrical Activity. Part II

In modern life sciences, the issue of a specific, exogenously directed manipulation of a cell's biochemistry is a highly topical one. In the case of electrically excitable cells, the aim of the manipulation is to control the cells' electrical activity, with the result being either excitation with subsequent generation of an action potential or inhibition and suppression of the excitatory currents. The techniques of electrical activity stimulation are of particular significance in tackling the most challenging basic problem: figuring out how the nervous system of higher multicellular organisms functions. At this juncture, when neuroscience is gradually abandoning the reductionist approach in favor of the direct investigation of complex neuronal systems, minimally invasive methods for brain tissue stimulation are becoming the basic element in the toolbox of those involved in the field. In this review, we describe three approaches that are based on the delivery of exogenous, genetically encoded molecules sensitive to external stimuli into the nervous tissue. These approaches include optogenetics (overviewed in Part I), as well as chemogenetics and thermogenetics (described here, in Part II), which is significantly different not only in the nature of the stimuli and structure of the appropriate effector proteins, but also in the details of experimental applications. The latter circumstance is an indication that these are rather complementary than competing techniques.

Genetically Encoded Tools for Research of Cell Signaling and Metabolism under Brain Hypoxia

Hypoxia is characterized by low oxygen content in the tissues. The central nervous system (CNS) is highly vulnerable to a lack of oxygen. Prolonged hypoxia leads to the death of brain cells, which underlies the development of many pathological conditions. Despite the relevance of the topic, different approaches used to study the molecular mechanisms of hypoxia have many limitations. One promising lead is the use of various genetically encoded tools that allow for the observation of intracellular parameters in living systems. In the first part of this review, we provide the classification of oxygen/hypoxia reporters as well as describe other genetically encoded reporters for various metabolic and redox parameters that could be implemented in hypoxia studies. In the second part, we discuss the advantages and disadvantages of the primary hypoxia model systems and highlight inspiring examples of research in which these experimental settings were combined with genetically encoded reporters.

Ion channel engineering for modulation and de novo generation of electrical excitability

Ion channels play essential roles in regulating electrical properties of excitable tissues. By leveraging various ion channel gating mechanisms, scientists have developed a versatile set of genetically encoded tools to modulate intrinsic tissue excitability under different experimental settings. In this article, we will review how ion channels activated by voltage, light, small chemicals, stretch, and temperature have been customized to enable control of tissue excitability both in vitro and in vivo. Advantages and limitations of each of these ion channel-engineering platforms will be discussed and notable applications will be highlighted. Furthermore, we will describe recent progress on de novo generation of excitable tissues via expression of appropriate sets of engineered voltage-gated ion channels and discuss potential therapeutic implications.