Vertebrate endocrine systems are key controllers of the physiological processes that maintain homeostasis. Hormones are secreted from specialized cells and glands in response to dynamic external and/or internal conditions. These changes in hormone levels initiate adaptive responses aimed at returning the organism to homeostasis. Our research seeks to build a mechanistic understanding of how the endocrine system matches adaptive phenotypes with environmental circumstances.
Fishes experience significant challenges to maintaining homeostasis in the presence of large, and sometimes variable, osmotic and salt gradients with the external environment. In turn, they have evolved efficient mechanisms for detecting changes in internal and external salt conditions to initiate subsequent physiological responses. We leverage a variety of fish models (e.g., Mozambique tilapia,Atlantic salmon,mummichog,andzebrafish) that allow us to unravel how cellular and molecular processes underlie the physiology, development, and natural histories of animals residing in dynamic environments.
The first major theme of our research is to understand how pituitary hormones regulate organs that maintain hydromineral balance of the organism, namely the gill, kidney, urinary bladder, and gastrointestinal tract. We are particularly focused on identifying ion pumps, transporters, and channels regulated by prolactin signaling (see Breves et al., 2014 and Breves et al., 2020). Furthermore, specialized ion-transporting cells within the gill, coined "ionocytes", mount osmotic stress responses when exposed to changes in environmental salinity. We are currently investigating the interplay between cellular stress responses and systemic prolactin signaling to further contribute mechanistic insight into how hormones control vertebrate epithelial tissues.
The sensitivity of prolactin-secreting cells of the tilapia pituitary gland to variations in extracellular osmolality enables investigations into how osmoreception underlies adaptive patterns of hormone secretion. While prolactin is firmly established as a necessary factor for osmoregulation in freshwater environments, it remains unknown how osmoreceptive processes orchestrate the expression of multiple prolactin-encoding genes. The second major theme of our research is to therefore link molecular aspects of cellular osmoreception with the regulatory control of prolactin gene promoters (see Seale et al., 2020). Based on our findings, other vertebrate genomes can be searched for essential promoter regions and/or transcription factors that respond to changes in extracellular osmolality.
Finally, the third major theme of our research is to determine how the somatotropic axis (the growth hormone/insulin-like growth-factor system) matches growth patterns with environmental conditions. More specifically, we focus on how stressors, nutrition, salinity, and xenobiotics modulate the expression of insulin-like growth-factor binding proteins in Atlantic salmon and tilapia (see Breves et al., 2018, Breves et al., 2020, and this short animation). Atlantic salmon life-history transitions are deeply interconnected with somatic growth patterns and body size underlies overall fitness at key stages. A nuanced understanding of how growth is regulated equips physiologists to more precisely infer the growth patterns of wild fish and to optimize restoration strategies for endangered populations.
- Recent Publications -
Enhanced expression of ncc1 and clc2c in the kidney and urinary bladder accompanies freshwater acclimation in Mozambique tilapia
Jason P. Breves, Nastasia N. Nelson, Victor Koltenyuk, Cody K. Petro-Sakuma, Fritzie T. Celino-Brady, Andre P. Seale
Comparative Biochemistry and Physiology - Part A (2021). 260, 111021. PDF
Molecular mechanisms of Cl- transport in fishes: new insights and their evolutionary context
Ciaran A. Shaughnessy, Jason P. Breves
Journal of Experimental Zoology - Part A(2021). 335, 207-216.PDF
Transcriptional regulation of prolactin in a euryhaline teleost: characterization of gene promoters through in silico and transcriptomic analyses
Andre P. Seale, Gardi Hewage Tharindu Malintha, Fritzie T. Celino-Brady, Tony Head, Mahdi Belcaid, Yoko Yamaguchi, Darren T. Lerner, David A. Baltzegar, Russell J. Borski, Zoia R. Stoytcheva, Jason P. Breves
Journal of Neuroendocrinology (2020). 32, e12905.PDF
Osmoregulatory actions of prolactin in the gastrointestinal tract of fishes
Jason P. Breves, Emily E. Popp, Eva F. Rothenberg, Clarence W. Rosenstein, Kaitlyn M. Maffett, Rebecca R. Guertin
General and Comparative Endocrinology (2020). 298, 113589. PDF
Cortisol regulates insulin-like growth-factorbinding protein (igfbp) gene expression in Atlantic salmon parr
Jason P. Breves, Ryan H. Springer-Miller, Demaris A. Chenoweth, Amanda L. Paskavitz, Annaliese Y. H. Chang, Amy M. Regish, Ingibjorg E. Einarsdottir, B. Thrandur Bjornsson, Stephen D. McCormick
Molecular and Cellular Endocrinology (2020). 518, 110989. PDF
Growth hormone regulates intestinal gene expression of nutrient transporters in tilapia (Oreochromis mossambicus)
Cody Petro-Sakuma, Fritzie T. Celino-Brady, Jason P. Breves, Andre P. Seale
General and Comparative Endocrinology (2020). 292, 113464. PDF
Salinity dependent expression of ncc2 in opercular epithelium and gill of mummichog (Fundulus heteroclitus)
Jason P. Breves, Julie A. Starling, Christine M. Popovski, James M. Doud, Christian K. Tipsmark
Journal of Comparative Physiology B (2020). 190, 219-230. PDF
Hormonal control of aquaporins in fishes
Jason P. Breves
In: Litwack, G (Ed.), Aquaporin Regulation, Vitamins and Hormones (2020). 112, 265-287. PDF
The primary objective of this course is to compare and contrast the functions of key physiological systems in the major vertebrate taxonomic groups (jawless fishes, cartilaginous fishes, bony fishes, amphibians, reptiles, birds, and mammals). Students are challenged to understand the mechanisms that support environmental adaptation at multiple levels of biological organization and the selection pressures that underlie their evolution.
This course is designed for upper-division students to concentrate on the physiological systems that maintain homeostasis in mammals. The physiological functions of these systems are further considered in light of their association with human and animal diseases. This course also takes the opportunity to explore specialized physiologies which evolved within the mammalian lineage (e.g., lactation).
This advanced physiology course concentrates on how hormones coordinate fundamental processes in vertebrates such as growth, development, metabolism, stress, and reproduction. Through the comparative approach students garner an understanding of how hormone actions evolved during the course of vertebrate evolution and how knowledge of these actions is leveraged in diverse fields. This course encompasses topics in endocrinology that reach from the physiology of wild animals to the etiology of human diseases. In this particular course, guest speakers play an important role in communicating the varied career paths that individuals pursue within the field of endocrinology.
Advanced Aquatic Animal Physiology
In this course, students study the physiological systems that enable animals to adapt to the conditions (e.g., temperature, salinity, oxygen, light, pressure) of aquatic habitats. Students consider from multiple perspectives (organismal, organ, tissue, cellular, and molecular) how the operation of physiological systems within invertebrates and vertebrates enables survival and reproduction in freshwater, estuarine, and marine environments.
“Professor and student learn from each other; it is a two-way interaction.…The differences between professor and student that derive from age, gender, economic status, ethnicity, experience, philosophy, etc., assure that both will be exposed to new ideas and attitudes.”
Nastasia characterizes the gene expression of solute transporters in the kidney and urinary bladder of Mozambique tilapia responding to changes in environmental salinity.
Victor Koltenyuk '20
Victor is reverse transcribing RNA purified from Atlantic salmon gills collected during their springtime preparation for seawater entry.
Annaliese Chang '19
Annaliese presents her poster on the effects of corticosteroids on the somatotropic axis of Atlantic salmon parr at the 2019 Experimental Biology Conference in Orlando, FL. Annaliese's poster was awarded second place in the Scholander Award Session held by the Comparative and Evolutionary Physiology Section of the American Physiological Society.
Becca White '19
Becca describes how steroid hormones regulate activities within the somatotropic axis of Atlantic salmon smolts acclimated to seawater and freshwater. Becca presented her findings at the 2019 Experimental Biology Conference in Orlando, FL.
James Doud '17
James presents his poster on salinity acclimation in mummichogs within the Comparative and Evolutionary Physiology Section at the 2017 Experimental BiologyConference in Chicago, IL.
Ryan Springer-Miller '17
Ryan presents her poster on how cortisol impacts salmon growth via insulin-like growth-factor binding proteins within the Comparative and Evolutionary Physiology Section at the 2017 Experimental Biology Conference in Chicago, IL.
Silas Phipps Costin '16
Silas monitors water conditions within our dedicated Aquatics Facility designed to house multiple wild-type and transgenic fish lines.