University of Kentucky UKnowledge University of Kentucky Doctoral Dissertations Graduate School 2009 TRANSCRIPTIONAL AND MORPHOLOGICAL CHANGES DURING THYROXINE-INDUCED METAMORPHOSIS OF THE MEXICAN AXOLOTL AND AXOLOTL-TIGER SALAMANDER HYBRIDS Robert Bryce Page University of Kentucky, [email protected] Right click to open a feedback form in a new tab to let us know how this document benefits ou.y Recommended Citation Page, Robert Bryce, "TRANSCRIPTIONAL AND MORPHOLOGICAL CHANGES DURING THYROXINE- INDUCED METAMORPHOSIS OF THE MEXICAN AXOLOTL AND AXOLOTL-TIGER SALAMANDER HYBRIDS" (2009). University of Kentucky Doctoral Dissertations. 774. https://uknowledge.uky.edu/gradschool_diss/774 This Dissertation is brought to you for free and open access by the Graduate School at UKnowledge. It has been accepted for inclusion in University of Kentucky Doctoral Dissertations by an authorized administrator of UKnowledge. For more information, please contact [email protected]. ABSTRACT OF DISSERTATION Robert Bryce Page The Graduate School University of Kentucky 2009 TRANSCRIPTIONAL AND MORPHOLOGICAL CHANGES DURING THYROXINE-INDUCED METAMORPHOSIS OF THE MEXICAN AXOLOTL AND AXOLOTL-TIGER SALAMANDER HYBRIDS ________________________________ ABSTRACT OF DISSERTATION _________________________________ A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the College of Arts and Sciences at the University of Kentucky By Robert Bryce Page Lexington, Kentucky Director: Dr. S. Randal Voss, Associate Professor of Biology Lexington, Kentucky 2009 Copyright © Robert Bryce Page 2009 ABSTRACT OF DISSERTATION TRANSCRIPTIONAL AND MORPHOLOGICAL CHANGES DURING THYROXINE-INDUCED METAMORPHOSIS OF THE MEXICAN AXOLOTL AND AXOLOTL-TIGER SALAMANDER HYBRIDS For nearly a century, amphibian metamorphosis has served as an important model of how thyroid hormones regulate vertebrate development. Consequently metamorphosis has been studied in a number of ways including: morphologically, developmentally, ecologically, and from an endocrine perspective. Over the last two decades, much has been learned about the molecular basis of anuran (frog) metamorphosis. However, very little is known about the molecular underpinnings of urodele (salamander) metamorphosis. Using the axolotl and axolotl hybrids as models, I present some of the first studies on the gene expression changes that occur during urodele metamorphosis. In Chapter 1, the motivation for the research described in the subsequent chapters is presented and the literature is briefly reviewed. In Chapter 2, the first microarray analysis of urodele metamorphosis is presented. This analysis shows that hundreds of genes are differentially expressed during thyroid hormone-induced metamorphic skin remodeling. Chapter 3 extends the analysis presented in Chapter 2 by showing that the transcriptional patterns associated with metamorphic skin remodeling are robust even when the concentration of thyroid hormone used to induce metamorphosis is varied by an order of magnitude. Chapter 4 makes use of the differentially expressed genes identified in Chapters 2 and 3 to articulate the first model of urodele metamorphosis to integrate changes in morphology, gene expression, and histology. In addition, Chapter 4 outlines a novel application for piecewise linear regression. In turn, Chapter 5 makes use of the model presented in Chapter 4 to demonstrate that full siblings segregating profound variation in metamorphic timing begin to diverge in phenotype early during larval development. In Chapter 6 the conclusions drawn from the research are summarized and future directions are suggested. KEYWORDS: Amphibian Metamorphosis, Mexican Axolotl, Morphometrics, Thyroid Hormone, Transcription Robert Bryce Page 29 October 2009 TRANSCRIPTIONAL AND MORPHOLOGICAL CHANGES DURING THYROXINE-INDUCED METAMORPHOSIS OF THE MEXICAN AXOLOTL AND AXOLOTL-TIGER SALAMANDER HYBRIDS By Robert Bryce Page S. Randal Voss Director of Dissertation Brian C. Rymond Director of Graduate Studies 29 October 2009 RULES FOR THE USE OF DISSERTATIONS Unpublished dissertations submitted for the Doctor’s degree and deposited in the University of Kentucky Library are as a rule open for inspection, but are to be used only with due regard to the rights of the authors. Bibliographical references may be noted, but quotations or summaries of parts may be published only with the permission of the author, and with the usual scholarly acknowledgments. Extensive copying or publication of the dissertation in whole or in part also requires the consent of the Dean of the Graduate School of the University of Kentucky. A library that borrows this dissertation for use by its patrons is expected to secure the signature of each user. Name Date ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ DISSERTATION Robert Bryce Page The Graduate School University of Kentucky 2009 TRANSCRIPTIONAL AND MORPHOLOGICAL CHANGES DURING THYROXINE-INDUCED METAMORPHOSIS OF THE MEXICAN AXOLOTL AND AXOLOTL-TIGER SALAMANDER HYBRIDS _________________________________ DISSERTATION _________________________________ A dissertation submitted in partial fulfillment of the the requirements for the degree of Doctor of Philosophy in the College of Arts and Sciences at the University of Kentucky By Robert Bryce Page Lexington, Kentucky Director: Dr. S. Randal Voss, Associate Professor of Biology Lexington, Kentucky 2009 Copyright © Robert Bryce Page 2009 FOR MY PARENTS, RICHARD C. AND ANNE M. PAGE ACKNOWLEDGMENTS After doing something as involved as a doctoral dissertation in the natural sciences, it’s hard to know where to begin when it comes to thanking people. This is particularly true when one has well over half a decade invested in getting into a doctoral program in the first place. Therefore I’d like to thank people who helped put me in this position through their academic mentorship during my time at institutions other than the University of Kentucky including: Carlos Camp, Lu Elrod, Bob Jaeger, Paul Leberg, Joe Neigel, and David Marsh. After I arrived at the University of Kentucky, a number of people have been helpful in different ways. In particular, I’d like to thank Randal Voss for taking me on as a graduate student and exposing me to the worlds of functional and comparative genomics. In addition, Phil Crowley and David Weisrock have continuously provided good advice and lent a kind ear. Arny Stromberg and Craig Sargent have both consistently taken time out of their days to discuss statistical issues, and this has undoubtedly improved the content of this dissertation. Finally, I’d like to thank the graduate students, techs, and additional scientists that have been collaborators during my time at the University of Kentucky. In particular thanks are due to: Chris Beachy, Meredith Boley, Kevin Kump, James Monaghan, Sri Putta, Amy Samuels, Jeramiah Smith, and John Walker. Like most trying endeavors, completing a doctoral degree in the natural sciences is not something that can be done without the continuous support of loved ones (or at least if it can be… I’m glad that I didn’t have to do it). My long-time partner Paige McMurry has provided unending support and put up with me for countless hours when I was absolutely no fun to be around. Likewise my parents, Richard C. and Anne M. Page have provided incredible support and understanding throughout this entire process. Finally, I’d like to thank several of my friends who have provided support and served as much needed distractions from my dissertation research including: Emily Bruner, Carol Dyer, Chris Ewing, Ira Fahrnam, Damon Ivey, Ian Henneberger, Joe Henneberger, Jason McAlister, Byran McCord, Dave McLeroy, Mike See, and Dave Smith. You are all reminders to me that the most important things that we build and achieve in our lifetimes are meaningful relationships with other human beings. iii TABLE OF CONTENTS Acknowledgments.............................................................................................................. iii List of Tables ..................................................................................................................... vi List of Figures ................................................................................................................... vii List of Files ........................................................................................................................ ix Chapter One: Introduction ...................................................................................................1 Overview ..................................................................................................................1 Background and motivation .....................................................................................2 Chapter Two: Microarray analysis identifies keratin