Visualization of a blue light transmission area in living animals using light-induced nuclear translocation of fluorescent proteins

Camouflage Nanoparticles Enable in Situ Bioluminescence-Driven Optogenetic Therapy of Retinoblastoma

Optogenetic therapy has emerged as a promising technique for the treatment of ocular diseases; however, most optogenetic tools rely on external blue light to activate the photoswitch, whose relatively strong phototoxicity may induce retinal damage. Herein, we present the demonstration of camouflage nanoparticle-based vectors for in situ bioluminescence-driven optogenetic therapy of retinoblastoma. In biomimetic vectors, the photoreceptor CRY2 and its interacting partner CIB1 plasmid are camouflaged with folic acid ligands and luciferase NanoLuc-modified macrophage membranes. To conduct proof-of-concept research, this study employs a mouse model of retinoblastoma. In comparison to external blue light irradiation, the developed system enables an in situ bioluminescence-activated apoptotic pathway to inhibit tumor growth with greater therapeutic efficacy, resulting in a significant reduction in ocular tumor size. Furthermore, unlike external blue light irradiation, which causes retinal damage and corneal neovascularization, the camouflage nanoparticle-based optogenetic system maintains retinal structural integrity while avoiding corneal neovascularization.

Nanobody-based RFP-dependent Cre recombinase for selective anterograde tracing in RFP-expressing transgenic animals

Transgenic animals expressing fluorescent proteins are widely used to label specific cells and proteins. By using a split Cre recombinase fused with mCherry-binding nanobodies or designed ankyrin repeat proteins, we created Cre recombinase dependent on red fluorescent protein (RFP) (Cre-DOR). Functional binding units for monomeric RFPs are different from those for polymeric RFPs. We confirmed selective target RFP-dependent gene expression in the mouse cerebral cortex using stereotaxic injection of adeno-associated virus vectors. In estrogen receptor-beta (Esr2)-mRFP1 mice and gastrin-releasing peptide receptor (Grpr)-mRFP1 rats, we confirmed that Cre-DOR can be used for selective tracing of the neural projection from RFP-expressing specific neurons. Cellular localization of RFPs affects recombination efficiency of Cre-DOR, and light and chemical-induced nuclear translocation of an RFP-fused protein can modulate Cre-DOR efficiency. Our results provide a method for manipulating gene expression in specific cells expressing RFPs and expand the repertory of nanobody-based genetic tools.

Strategies for Targeting Neural Circuits: How to Manipulate Neurons Using Virus Vehicles

Viral strategies are the leading methods for mapping neural circuits. Viral vehicles combined with genetic tools provide the possibility to visualize entire functional neural networks and monitor and manipulate neural circuit functions by high-resolution cell type- and projection-specific targeting. Optogenetics and chemogenetics drive brain research forward by exploring causal relationships among different brain regions. Viral strategies offer a fresh perspective for the analysis of the structure-function relationship of the neural circuitry. In this review, we summarize current and emerging viral strategies for targeting neural circuits and focus on adeno-associated virus (AAV) vectors.

Detection of neuropeptides in vivo and open questions for current and upcoming fluorescent sensors for neuropeptides

During a stress response, various neuropeptides are secreted in a spatiotemporally coordinated way in the brain. For a precise understanding of peptide functions in a stress response, it is important to investigate when and where they are released, how they diffuse, and how they are broken down in the brain. In the past two decades, genetically encoded fluorescent calcium indicators have greatly advanced our knowledge of the functions of specific neuronal activity in regulation of behavioral changes and physiological responses during stress. In addition, various kinds of structural information on G-protein-coupled receptors (GPCRs) for neuropeptides have been revealed. Recently, genetically encoded fluorescent sensors have been developed for detection of neurotransmitters by making use of conformational changes induced by ligand binding. In this review, we summarize the recent and upcoming advances of techniques for detection of neuropeptides and then present several open questions that will be solved by application of recent or upcoming technical advances in detection of neuropeptides in vivo.