Calcium is a ubiquitous signaling molecule that regulates a large range of functions in cells, from vesicular release to homeostatic plasticity. Ca2+ can perform these diverse functions in part by acting in different spatial and temporal regimes. These range from small local transient events lasting milliseconds to cell wide elevations in cytosolic Ca2+ lasting minutes. Currently the main focus of the Parker lab is the IP3R, a Ca2+ channel located on the endoplasmic reticulum (ER). Upon binding both IP3 and Ca2+, the IP3R opens to release stored Ca2+ from within the ER lumen. Released Ca2+ can remain spatially restricted to a small cluster of IP3Rs to generate a local microdomain of Ca2+ (Ca2+ puff) or - depending on the proximity of neighboring IP3Rs - can propagate throughout a cell recruiting multiple puff sites through a process known as Ca2+ induced Ca2+ release.
I have worked with Dr. Ian Parker to construct a shadowless TIRF microscope which allows us to visualize the subcellular concentration of Ca2+ with high temporal and spatial precision. By uncaging IP3, we can activate IP3Rs and measure the resulting Ca2+ puffs. I have previously developed an algorithm which automates the detection these Ca2+ puffs and extracts their spatiotemporal parameters. I am currently developing another algorithm - based on techniques employed in superresolution microscopy - which uses single channel Ca2+ events to determine with nanometer precision the location of individual IP3 receptors. I hope this will help uncover the structure of IP3R clusters, knowledge of which is required to understand their function.
Figueroa D.X., Ellefsen K.L., Hathaway E.R. Yang M.C., Carathedathu M.C., Gandhi S.P Contribution of innate cortical mechanisms to the maturation of orientation selectivity in Parvalbumin interneurons. Journal of Neuroscience (2017)
Dickenson G.D., Ellefsen K.L., Dawson S.P., Pearson J.E., Parker I. Hindered cytoplasmic diffusion of inositol trisphosphate restricts its cellular range of action. Science Signaling (2016)
Ellefsen K.L., Dynes J.L., Parker I. Spinning-spot Shadowless TIRF Microscopy. PlosONE (2015)
Lock, J.T., Ellefsen K.L., Settle B., Parker I., Smith I.F. Imaging Local Ca2+ Signals in Cultured Mammalian Cells. Jove (2015).
Ellefsen K.L., Settle B., Parker I., Smith I.F. An algorithm for automated detection, localization and measurement of local calcium signals from camera-based imaging. Cell Calcium (2014).
Allison, D.W, Wilcox, B.S., Ellefsen, K.L., Askew, C.E., Hansen, D.M., Wilcox, J., Sandoval, S.S., Eggett, D., Yanagawa,Y., Steffensen, S.C. Mefloquine effects on Ventral Tegmental Area Dopamine and GABA Neuron Inhibition: a Physiologic Role for Connexin-36 Gap Junctions. Synapse (2011)
Flika was created in the Parker Lab in order to detect and measure Ca2+ puffs caused by IP3 channel openings. It is growing into a general analysis tool for biological movies. For instance, it can track rodents.
GLAMS is a web based tool to help researchers keep track of their colony and the experiments performed on individual animals. The program stores all the information in a MySQL database. It contains a web server which, when launched, allows users to retrieve and update information on the database.
I am a graduate student in Neurobiology and Behavior at the University of California, Irvine. I want to mathematically describe how electrical signaling between neurons in the brain processes information.