Browsing by Author "Ni, Lina"
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- Cool and warm ionotropic receptors control multiple thermotaxes in Drosophila larvaeOmelchenko, Alisa A.; Bai, Hua; Spina, Emma C.; Tyrrell, Jordan J.; Wilbourne, Jackson T.; Ni, Lina (Frontiers, 2022-11)Animals are continuously confronted with different rates of temperature variation. The mechanism underlying how temperature-sensing systems detect and respond to fast and slow temperature changes is not fully understood in fly larvae. Here, we applied two-choice behavioral assays to mimic fast temperature variations and a gradient assay to model slow temperature changes. Previous research indicates that Rhodopsin 1 (Rh1) and its phospholipase C (PLC) cascade regulate fast and slow temperature responses. We focused on the ionotropic receptors (IRs) expressed in dorsal organ ganglions (DOG), in which dorsal organ cool-activated cells (DOCCs) and warm-activated cells (DOWCs) rely on IR-formed cool and warm receptors to respond to temperature changes. In two-choice assays, both cool and warm IRs are sufficient for selecting 18 degrees C between 18 degrees C and 25 degrees C but neither function in cool preferences between 25 degrees C and 32 degrees C. The Rh1 pathway, on the other hand, contributes to choosing preferred temperatures in both assays. In a gradient assay, cool and warm IR receptors exert opposite effects to guide animals to similar to 25 degrees C. Cool IRs drive animals to avoid cool temperatures, whereas warm IRs guide them to leave warm regions. The Rh1 cascade and warm IRs may function in the same pathway to drive warm avoidance in gradient assays. Moreover, IR92a is not expressed in temperature-responsive neurons but regulates the activation of DOWCs and the deactivation of DOCCs. Together with previous studies, we conclude that multiple thermosensory systems, in various collaborative ways, help larvae to make their optimal choices in response to different rates of temperature change.
- Functional Labeling of Individualized Post-Synaptic Neurons using Optogenetics and trans-TangoCastaneda, Allison Nicole (Virginia Tech, 2023-07-11)Neural circuitry, or how neurons connect across brain regions to form functional units, is the fundamental basis of all brain processing and behavior. There are several neural circuit analysis tools available across different model organisms, but currently the field lacks a comprehensive method that can 1) target post-synaptic neurons using a pre-synaptic driver line, 2) assess post-synaptic neuron morphology, and 3) test behavioral response of the post-synaptic neurons in an isolated manner. This work will present FLIPSOT, or Functional Labeling of Individualized Post-Synaptic Neurons using Optogenetics and trans-Tango, which is a method developed to fulfill all three of these conditions. FLIPSOT uses a pre-synaptic driver line to drive trans-Tango, triggering heat-shock-dependent expression of post-synaptic optogenetic receptors. When heat shocked for a suitable duration of time, optogenetic activation or inhibition is made possible in a randomized selection of post-synaptic cells, allowing testing and comparison of function. Finally, imaging of each brain confirms which neurons were targeted per animal, and analysis across trials can reveal which post-synaptic neurons are necessary and/or sufficient for the relevant behavior. FLIPSOT is then tested within Drosophila melanogaster to evaluate the necessity and sufficiency of post-synaptic neurons in the Drosophila Heating Cell circuit, which is a circuit that functions to drive warmth avoidance behavior. FLIPSOT presents a new combinatory tool for evaluation of behavioral necessity and sufficiency of post-synaptic cells. The tool can easily be utilized to test many different behaviors and circuits through modification of the pre-synaptic driver line. Lastly, the success of this tool within flies paves the way for possible future adaptation in other model organisms, including mammals.
- Ionotropic Receptor-dependent cool cells control the transition of temperature preference in Drosophila larvaeTyrrell, Jordan J.; Wilbourne, Jackson T.; Omelchenko, Alisa A.; Yoon, Jin; Ni, Lina (PLOS, 2021-04-01)Temperature sensation guides animals to avoid temperature extremes and to seek their optimal temperatures. The larval stage of Drosophila development has a dramatic effect on temperature preference. While early-stage Drosophila larvae pursue a warm temperature, late-stage larvae seek a significantly lower temperature. Previous studies suggest that this transition depends on multiple rhodopsins at the late larval stage. Here, we show that early-stage larvae, in which dorsal organ cool cells (DOCCs) are functionally blocked, exhibit similar cool preference to that of wild type late-stage larvae. The molecular thermoreceptors in DOCCs are formed by three members of the Ionotropic Receptor (IR) family, IR21a, IR93a, and IR25a. Early-stage larvae of each Ir mutant pursue a cool temperature, similar to that of wild type late-stage larvae. At the late larval stage, DOCCs express decreased IR proteins and exhibit reduced cool responses. Importantly, late-stage larvae that overexpress IR21a, IR93a, and IR25a in DOCCs exhibit similar warm preference to that of wild type early-stage larvae. These data suggest that IR21a, IR93a, and IR25a in DOCCs navigate early-stage larvae to avoid cool temperatures and the reduction of these IR proteins in DOCCs results in animals remaining in cool regions during the late larval stage. Together with previous studies, we conclude that multiple temperature-sensing systems are regulated for the transition of temperature preference in fruit fly larvae.
- The Ionotropic Receptors IR21a and IR25a mediate cool sensing in DrosophilaNi, Lina; Klein, Mason; Svec, Kathryn V.; Budelli, Gonzalo; Chang, Elaine C.; Ferrer, Anggie J.; Benton, Richard; Samuel, Aravinthan D. T.; Garrity, Paul A. (eLife Sciences Publications, 2016-04-29)Animals rely on highly sensitive thermoreceptors to seek out optimal temperatures, but the molecular mechanisms of thermosensing are not well understood. The Dorsal Organ Cool Cells (DOCCs) of the Drosophila larva are a set of exceptionally thermosensitive neurons critical for larval cool avoidance. Here, we show that DOCC cool-sensing is mediated by Ionotropic Receptors (IRs), a family of sensory receptors widely studied in invertebrate chemical sensing. We find that two IRs, IR21a and IR25a, are required to mediate DOCC responses to cooling and are required for cool avoidance behavior. Furthermore, we find that ectopic expression of IR21a can confer coolresponsiveness in an Ir25a-dependent manner, suggesting an instructive role for IR21a in thermosensing. Together, these data show that IR family receptors can function together to mediate thermosensation of exquisite sensitivity.
- The Structure and Function of Ionotropic Receptors in DrosophilaNi, Lina (2021-02-01)Ionotropic receptors (IRs) are a highly divergent subfamily of ionotropic glutamate receptors (iGluR) and are conserved across Protostomia, a major branch of the animal kingdom that encompasses both Ecdysozoa and Lophothrochozoa. They are broadly expressed in peripheral sensory systems, concentrated in sensory dendrites, and function in chemosensation, thermosensation, and hygrosensation. As iGluRs, four IR subunits form a functional ion channel to detect environmental stimuli. Most IR receptors comprise individual stimulus-specific tuning receptors and one or two broadly expressed coreceptors. This review summarizes the discoveries of the structure of IR complexes and the expression and function of each IR, as well as discusses the future direction for IR studies.
- TACI: An ImageJ Plugin for 3D Calcium Imaging AnalysisOmelchenko, Alisa A.; Bai, Hua; Hussain, Sibtain; Tyrrell, Jordan J.; Klein, Mason; Ni, Lina (Journal of Visualized Experiments, 2022-12-16)Research in neuroscience has evolved to use complex imaging and computational tools to extract comprehensive information from data sets. Calcium imaging is a widely used technique that requires sophisticated software to obtain reliable results, but many laboratories struggle to adopt computational methods when updating protocols to meet modern standards. Difficulties arise due to a lack of programming knowledge and paywalls for software. In addition, cells of interest display movements in all directions during calcium imaging. Many approaches have been developed to correct the motion in the lateral (x/y) direction. This paper describes a workflow using a new ImageJ plugin, TrackMate Analysis of Calcium Imaging (TACI), to examine motion on the z-axis in 3D calcium imaging. This software identifies the maximum fluorescence value from all the z-positions a neuron appears in and uses it to represent the neuron's intensity at the corresponding t-position. Therefore, this tool can separate neurons overlapping in the lateral (x/ y) direction but appearing on distinct z-planes. As an ImageJ plugin, TACI is a user-friendly, open-source computational tool for 3D calcium imaging analysis. We validated this workflow using fly larval thermosensitive neurons that displayed movements in all directions during temperature fluctuation and a 3D calcium imaging dataset acquired from the fly brain.
- Using Drosophila Two-Choice Assay to Study Optogenetics in Hands-On Neurobiology Laboratory ActivitiesFu, Zhuo; Huda, Ainul; Kimbrough, Ian F.; Ni, Lina (Faculty for Undergraduate Neuroscience, 2023)Optogenetics has made a significant impact on neuroscience, allowing activation and inhibition of neural activity with exquisite spatiotemporal precision in response to light. In this lab session, we use fruit flies to help students understand the fundamentals of optogenetics through hands-on activities. The CsChrimson channelrhodopsin, a light-activated cation channel, is expressed in sweet and bitter sensory neurons. Sweet sensory neurons guide animals to identify nutrient-rich food and drive appetitive behaviors, while bitter sensory neurons direct animals to avoid potentially toxic substances and guide aversive behavior. Students use two-choice assays to explore the causality between the stimulation activation of these neurons and the appetitive and avoidance behaviors of the fruit flies. To quantify their observations, students calculate preference indices and use the Student’s t-test to analyze their data. After this lab session, students are expected to have a basic understanding of optogenetics, fly genetics, sensory perception, and how these relate to sensory-guided behaviors. They will also learn to conduct, quantify, and analyze two-choice behavioral assays.