Showing 1 - 6 of 6 results
Imaging of Morphological and Biochemical Hallmarks of Apoptosis with Optimized Optogenetic Actuators.
The creation of optogenetic switches for specific activation of cell-death pathways can provide insights into apoptosis and could also form a basis for non-invasive, next-generation therapeutic strategies. Previous work has demonstrated that cryptochrome 2 (Cry2)/CIB, a blue light–activated protein–protein dimerization module from the plant Arabidopsis thaliana together with BCL2-associated X apoptosis regulator (BAX), an outer mitochondrial membrane (OMM)-targeting pro-apoptotic protein, can be used for light-mediated initiation of mitochondrial outer-membrane permeabilization (MOMP) and downstream apoptosis. In this work, we further developed the original light-activated Cry2–BAX system (henceforth referred to as OptoBAX) by improving the photophysical properties and light-independent interactions of this optogenetic switch. The resulting optogenetic constructs significantly reduced the frequency of light exposure required for the membrane permeabilization activation and also decreased dark-state cytotoxicity. We used OptoBAX in a series of experiments in Neuro-2a and HEK293T cells to measure the timing of the dramatic morphological and biochemical changes occurring in cells after light-induced MOMP. In these experiments, we used OptoBAX in tandem with fluorescent reporters for imaging key events in early apoptosis, including membrane inversion, caspase cleavage, and actin redistribution. We then used these data to construct a timeline of biochemical and morphological events in early apoptosis, demonstrating a direct link between MOMP-induced redistribution of actin and apoptosis progression. In summary, we have created a next-generation Cry2/CIB–BAX system requiring less frequent light stimulation and established a timeline of critical apoptotic events, providing detailed insights into key steps in early apoptosis.
Optical induction of autophagy via Transcription factor EB (TFEB) reduces pathological tau in neurons.
Aggregation and accumulation of microtubule associated protein tau in neurons is major neuropathological hallmark of Alzheimer’s disease (AD) and related tauopathies. Attempts have been made to promote clearance of pathological tau (p-Tau) from neurons via autophagy. Over expression of transcription factor EB (TFEB), has shown to clear pTau from neurons via autophagy. However, sustained TFEB activation and/or autophagy can create burden on cellular bioenergetics and can be deleterious. Thus, we engineered a minimally invasive optical system that could transiently alter autophagic flux. We optimized and testedan optogenetic gene expression system derived from apreviouslyengineered bacterial transcription factor, EL222. For the first time, our group utilized this system not only to spatial-temporally control nuclear TFEB expression, we also show light-induced TFEB has the capacity to reduce p-Tau burden in AD patient-derived human iPSC-neurons. Together, these results suggest that optically-regulatable gene expression of TFEB unlocks opto-therapeutics to treat AD and other dementias.
Near-infrared light-controlled gene expression and protein targeting in neurons and non-neuronal cells.
Near-infrared (NIR) light-inducible binding of bacterial phytochrome BphP1 to its engineered partner QPAS1 is used for optical protein regulation in mammalian cells. However, there are no data on the application of the BphP1-QPAS1 pair in cells derived from various mammalian tissues. Here, we tested functionality of two BphP1-QPAS1-based optogenetic tools, such as an NIR and blue light-sensing system for control of protein localization (iRIS) and an NIR light-sensing system for transcription activation (TA), in several cell types including cortical neurons. We found that the performance of these optogenetic tools often rely on physiological properties of a specific cell type, such as nuclear transport, which may limit applicability of blue light-sensitive component of iRIS. In contrast, the NIR-light-sensing part of iRIS performed well in all tested cell types. The TA system showed the best performance in HeLa, U-2 OS and HEK-293 cells. Small size of the QPAS1 component allows designing AAV viral particles, which were applied to deliver the TA system to neurons.
Smartphone-controlled optogenetically engineered cells enable semiautomatic glucose homeostasis in diabetic mice.
With the increasingly dominant role of smartphones in our lives, mobile health care systems integrating advanced point-of-care technologies to manage chronic diseases are gaining attention. Using a multidisciplinary design principle coupling electrical engineering, software development, and synthetic biology, we have engineered a technological infrastructure enabling the smartphone-assisted semiautomatic treatment of diabetes in mice. A custom-designed home server SmartController was programmed to process wireless signals, enabling a smartphone to regulate hormone production by optically engineered cells implanted in diabetic mice via a far-red light (FRL)-responsive optogenetic interface. To develop this wireless controller network, we designed and implanted hydrogel capsules carrying both engineered cells and wirelessly powered FRL LEDs (light-emitting diodes). In vivo production of a short variant of human glucagon-like peptide 1 (shGLP-1) or mouse insulin by the engineered cells in the hydrogel could be remotely controlled by smartphone programs or a custom-engineered Bluetooth-active glucometer in a semiautomatic, glucose-dependent manner. By combining electronic device-generated digital signals with optogenetically engineered cells, this study provides a step toward translating cell-based therapies into the clinic.
Regulation of neural gene transcription by optogenetic inhibition of the RE1-silencing transcription factor.
Optogenetics provides new ways to activate gene transcription; however, no attempts have been made as yet to modulate mammalian transcription factors. We report the light-mediated regulation of the repressor element 1 (RE1)-silencing transcription factor (REST), a master regulator of neural genes. To tune REST activity, we selected two protein domains that impair REST-DNA binding or recruitment of the cofactor mSin3a. Computational modeling guided the fusion of the inhibitory domains to the light-sensitive Avena sativa light-oxygen-voltage-sensing (LOV) 2-phototrophin 1 (AsLOV2). By expressing AsLOV2 chimeras in Neuro2a cells, we achieved light-dependent modulation of REST target genes that was associated with an improved neural differentiation. In primary neurons, light-mediated REST inhibition increased Na(+)-channel 1.2 and brain-derived neurotrophic factor transcription and boosted Na(+) currents and neuronal firing. This optogenetic approach allows the coordinated expression of a cluster of genes impinging on neuronal activity, providing a tool for studying neuronal physiology and correcting gene expression changes taking place in brain diseases.
Optical control of mammalian endogenous transcription and epigenetic states.
The dynamic nature of gene expression enables cellular programming, homeostasis and environmental adaptation in living systems. Dissection of causal gene functions in cellular and organismal processes therefore necessitates approaches that enable spatially and temporally precise modulation of gene expression. Recently, a variety of microbial and plant-derived light-sensitive proteins have been engineered as optogenetic actuators, enabling high-precision spatiotemporal control of many cellular functions. However, versatile and robust technologies that enable optical modulation of transcription in the mammalian endogenous genome remain elusive. Here we describe the development of light-inducible transcriptional effectors (LITEs), an optogenetic two-hybrid system integrating the customizable TALE DNA-binding domain with the light-sensitive cryptochrome 2 protein and its interacting partner CIB1 from Arabidopsis thaliana. LITEs do not require additional exogenous chemical cofactors, are easily customized to target many endogenous genomic loci, and can be activated within minutes with reversibility. LITEs can be packaged into viral vectors and genetically targeted to probe specific cell populations. We have applied this system in primary mouse neurons, as well as in the brain of freely behaving mice in vivo to mediate reversible modulation of mammalian endogenous gene expression as well as targeted epigenetic chromatin modifications. The LITE system establishes a novel mode of optogenetic control of endogenous cellular processes and enables direct testing of the causal roles of genetic and epigenetic regulation in normal biological processes and disease states.