Associate Research Professor, PBRC
Postdoctoral, University of Pennsylvania School of Medicine (Neuroscience)
Ph.D., Brandeis University (Biology)
A.B., Bowdoin College (Biology)
Project 1. What underlies neural networks variability in the responses to different hormonal inputs?
This project addresses one of the fundamental questions in neuroscience: “what underlies variability in the responses of neural networks to different inputs?”. In particular, the project focuses on the responses of central pattern generators and the rhythmic outputs they generate to modulatory inputs, e.g. circulating peptide hormones. Although this question can be addressed on a number of levels, our focus of is on understanding the molecular underpinnings of variability, particularly the basis for different physiological responses to the same modulator in different individuals. For our research we are using the cardiac and stomatogastric neuromuscular systems of decapod crustaceans as they provide some of the simplest model systems in the animal kingdom for understanding this phenomenon. The data gathered from these simple crustacean models will provide critical information on the mechanism(s) underlying neural networks responses to different inputs, information that can be applied to more complex systems across the animal kingdom.
Project 2. Do the molecular cascades that give rise to distinct timing regimes utilize common or unique genetic machinery?
This project addresses a fundament question in the field of chronobiology: “do the molecular cascades that give rise to distinct timing regimes utilize common or unique genetic machinery?”. The precise timing of biological processes is a key component of physiological and behavioral control in all living organisms. To date, a myriad of timing regimes have been documented, including many operating on different time courses within a single species. The presence of multiple “clock” systems that operate on different timing cycles within a species raises a fundamental question for the field of chronobiology: “do the molecular cascades that give rise to biological clocks operating on different time scales use common or unique sets of genes/proteins to affect physiological/behavioral output?”. To address this question we are using a variety of crustaceans as models, particularly intertidal marine species. Virtually all species express circadian rhythms, that is, physiological and behavioral patterns that oscillate with a period of approximately 24-h and are synchronized to the solar day. The persistence of these rhythms under constant laboratory conditions is generally taken as evidence for the existence of an innate, self-sustaining timekeeping mechanism, i.e. a biological clock. In addition to their circadian rhythms, species from intertidal habitats often express circatidal rhythms, oscillations in behavior and physiology attuned to the tidal cycle. Given that circadian rhythms are present in almost all extant organisms, including prokaryotes, the presence of two biological timing systems oscillating with different periods in intertidal organisms raises the interesting possibility that the circatidal system may have evolved from a pre-existing circadian system and might utilize the same molecular and cellular machinery. As a first step towards testing this hypothesis, we have begun to identify the molecular components and the neural substrates for circadian and circatidal oscillators in crustaceans. Behavioral circadian and circatidal rhythms have been studied in several intertidal invertebrates, including mollusks, annelids and crustaceans, but little is known about the neural and molecular components of these biological timing systems. Because the neurochemistry and neuroanatomy of crustaceans have been particularly well established (particularly for decapod species), these animals represent an ideal model in which to search for these components. Moreover, the close phylogenetic relationship between crustaceans and insects (where molecular and cellular components of the circadian system are well established in a number of species; e.g. Drosophila) provides both background information and biological reagents that are relevant and useful for this project.
Christie, A.E. 2015. Neuropeptide discovery in Eucyclops serrulatus (Crustacea, Copepoda): prediction of the first peptidome for a member of the Cyclopoida. Gen. Comp. Endocrinol. 211:92-105.
Christie, A.E. 2015. In silico characterization of the neuropeptidome of the Western black widow spider Latrodectus hesperus. Gen. Comp. Endocrinol. 210:63-80.
Nesbit, K.T., Christie, A.E. 2014. Identification of the molecular components of a Tigriopus californicus (Crustacea, Copepoda) circadian clock. Comp. Biochem. Physiol. Part D Genomics Proteomics. 12:16-44.
Christie, A.E. 2014. Expansion of the Litopenaeus vannamei and Penaeus monodon peptidomes using transcriptome shotgun assembly sequence data. Gen. Comp. Endocrinol. 206:235-254.
Christie, A.E. 2014. Identification of the first neuropeptides from the Amphipoda (Arthropoda, Crustacea). Gen. Comp. Endocrinol. 206:96-110.
Christie, A.E. 2014. In silico characterization of the peptidome of the sea louse Caligus rogercresseyi (Crustacea, Copepoda). Gen. Comp. Endocrinol. 204:248-260.
Christie, A.E. 2014. Peptide discovery in the ectoparasitic crustacean Argulus siamensis: identification of the first neuropeptides from a member of the Branchiura. Gen. Comp. Endocrinol. 204:114-125.
Christie, A.E., Fontanilla, T.M., Roncalli, V., Cieslak, M.C., Lenz, P.H. 2014. Gasotransmitter signaling in the copepod crustacean Calanus finmarchicus: identification of the biosynthetic enzymes of nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S) using a de novo assembled transcriptome. Gen. Comp. Endocrinol. 202:76-86.
Christie, A.E. 2014. Prediction of the peptidomes of Tigriopus californicus and Lepeophtheirus salmonis (Copepoda, Crustacea). Gen. Comp. Endocrinol. 201:87-106.
Christie, A.E. 2014. Prediction of the first neuropeptides from a member of the Remipedia (Arthropoda, Crustacea). Gen. Comp. Endocrinol. 201:74-86.
Lenz, P.H., Roncalli, V., Hassett, R.P., Wu, L., Cieslak, M.C., Hartline, D.H., Christie, A.E. 2014. De novo assembly of a transcriptome for Calanus finmarchicus (Crustacea, Copepoda) – the dominant zooplankter of the North Atlantic Ocean. PLoS One. 9:e88589.
Christie, A.E., Fontanilla, T.M., Roncalli, V., Cieslak, M.C., Lenz, P.H. 2014. Identification and developmental expression of the enzymes responsible for dopamine, histamine, octopamine and serotonin biosynthesis in the copepod crustacean Calanus finmarchicus. Gen. Comp. Endocrinol. 195:28-39.