Assistant Professor of Biology
Office phone: (413) 572-8718
Office: Wilson 215A
B.S., University of Massachusetts Amherst
Ph.D., University of Massachusetts Amherst
Postdoctoral Appt., Conte Anadromous Fish Research Center
Joined Westfield State University in 2019
BIOL 0205: Cell Biology (Lecture and Lab)
BIOL 0237: Human Anatomy and Physiology I (Lecture and Lab)
BIOL 0239: Human Anatomy and Physiology II (Lecture and Lab)
Fish osmoregulatory physiology: Fish in freshwater or seawater face different physiological challenges. In freshwater, diffusive ion loss and water gain must be counteracted by active ion uptake and retention, and dilute urine production. Conversely, in seawater, diffusive ion gain and water loss must be countered by active ion extrusion and increased water consumption. For fishes that remain in freshwater or seawater, the mechanisms that maintain ion homeostasis may be relatively static. On the other hand, fish which can adapt to freshwater and seawater, termed euryhaline, must do so by regulating the expression of proteins important for ion-transport and trans-epithelial resistance in tissues that are critical for maintaining ion-homeostasis, such as the gill. Gill ionocytes are a class of highly specialized cells that mediate ion transport between a fish and the aqueous environment. We are interested in how the morphology, and protein expression profiles, of these cells are related to the ability of euryhaline fish to move between freshwater and seawater environments.
Cytoskeleton: Cell morphology and function is dependent on the cytoskeleton, a network of protein filaments that are composed of actin (filamentous actin), tubulin (microtubules), or intermediate filaments. We recently described a unique arrangement of filamentous actin structures (white and red, image below) in the carapace integument of a small freshwater crustacean, Daphnia magna. Our current work aims to shed light on the form and function of these filamentous actin structures. What we learn about these structures in Daphnia stands to contribute to a broader understanding of actin dynamics, as actin is one of the most highly-conserved eukaryotic proteins.
Gow JB and Christensen AK. Medical terminology: Active learning through case studies. (2020, in press). Jones & Bartlett Learning, Burlington, MA.
Christensen AK and Gow JB. Rhabdomyolysis: A Workout Breakdown. 2019. National Center for Case Study Teaching in Science Case Collection. University of Buffalo. [PDF]
Christensen AK, Regish A, McCormick SD. Shifts in the relationship between mRNA and protein abundance of gill ion-transporters during smolt development and seawater acclimation in Atlantic salmon (Salmo salar). Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology. 2018 221: 63-73. [Abstract]
Christensen AK, *Owusu N, *Jean-Louis D. Carapace epithelia are rich in large filamentous actin bundles in Daphnia magna, Daphnia pulex and Sida crystallina (Crustacea: Cladocera). Invertebrate Biology. 2018 137: 49-59. [Abstract]
- Selected for cover image.
McCormick SD, Regish A, Christensen AK, Bjornsson TB. Differential regulation of sodium-potassium pump isoforms during smolt development and seawater exposure of Atlantic salmon. Journal of Experimental Biology. 2013 216: 1142-1151. [PDF]
Christensen AK, Hiroi J, Schultz ET, McCormick SD. Branchial ionocyte organization and ion transport protein expression in juvenile alewives acclimated to freshwater or seawater. Journal of Experimental Biology. 2012 215: 642-652. [PDF]
McCormick SD, Regish A, Christensen AK. Distinct freshwater and seawater isoforms of Na+/K+-ATPase in gill chloride cells of Atlantic salmon. Journal of Experimental Biology. 2009 212: 3994-4001. [PDF]
Christensen AK and Jensen AM. Tissue-specific requirements for specific domains within Moe/Epb4.1l5 during early zebrafish development. BMC Developmental Biology. 2008 8:3. [PDF]
- Selected for image of the month.
Hsu YC, Willoughby JJ, Christensen AK, Jensen AM. Mosaic Eyes is a novel component of the Crumbs complex and negatively regulates photoreceptor apical size. Development. 2006 133(24):4849-59. [PDF]
Newmyer SL, Christensen A, Sever S. Auxilin-dynamin interactions link the uncoating ATPase chaperone machinery with vesicle formation. Developmental Cell. 2003 4(6):929-40. [Abstract]