Evolution of Molecular Function in Mammalian Neurons
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University of Pennsylvania ScholarlyCommons Publicly Accessible Penn Dissertations Fall 2011 Evolution of Molecular Function in Mammalian Neurons Chantal Francis [email protected] Follow this and additional works at: https://repository.upenn.edu/edissertations Part of the Bioinformatics Commons, Biology Commons, Cell Biology Commons, and the Molecular Biology Commons Recommended Citation Francis, Chantal, "Evolution of Molecular Function in Mammalian Neurons" (2011). Publicly Accessible Penn Dissertations. 961. https://repository.upenn.edu/edissertations/961 This paper is posted at ScholarlyCommons. https://repository.upenn.edu/edissertations/961 For more information, please contact [email protected]. Evolution of Molecular Function in Mammalian Neurons Abstract A common question in neuroscience is what forms the neurological basis of the variety of behaviors in mammals. While many studies have compared mammalian anatomy and evolution, few have investigated the physiologic functions of individual neurons in a comparative manner. Neurons’ ability to modify their features in response to stimuli, known as synaptic plasticity, is fundamental for learning and memory. A key feature of synaptic plasticity involves delivering mRNA to distinct domains where they are locally translated. Regulatory coordination of these events is critical for synaptogenesis and synaptic plasticity as defects in these processes can lead to neurological diseases. In this work, we combine computational and experimental biology to investigate subcellular localization of mRNAs in dendrites of mouse and rat neurons. Differential subcellular localization of specific gene products may highlight differential synaptic function and allow the uncovering of evolutionary conserved as well as divergent molecular functions in neurons. First, we performed a comparative analysis of the dendritic transcriptome in mouse and rat via microarrays. We found that their dendritic transcriptome are significantly more divergent than other homologous tissues and that these evolutionarily changes could be associated with transposon activity. Second, we comprehensively determined subcellular expression patterns for neuronal genes in mice and rats via a systematic in situ survey on a curated list of dendritic mRNA from our previous microarray study. This survey highlighted that dendritic localization of specific transcripts occurs in a species- specific fashion. eW uncovered species-specific cis and trans-elements with possible implications in transcript localization and gene expression regulation in neurons. The interactions between these elements might play a major role in the proper development and evolution of complex nervous systems. Our data will be publically available in a database (http://kim.bio.upenn.edu/insitu/public/), which could guide future investigations. Finally, we investigated single cell variability by combining microarrays, RNAseq and in situ experiments. Our preliminary results underlined the extent of this variability and its contributions in establishing cell’s unique identity. In conclusion, our study suggests the existence of species-specific mRNA localization mechanisms and supports the idea that evolution of phenotypes might be linked to the evolution of subcellular localization of transcripts. Degree Type Dissertation Degree Name Doctor of Philosophy (PhD) Graduate Group Biology First Advisor Junhyong Kim Second Advisor Jim Eberwine Keywords mRNA, dendrites, localization, evolution Subject Categories Bioinformatics | Biology | Cell Biology | Molecular Biology This dissertation is available at ScholarlyCommons: https://repository.upenn.edu/edissertations/961 EVOLUTION OF MOLECULAR FUNCTION IN MAMMALIAN NEURONS Chantal Francis A DISSERTATION in Biology Presented to the Faculties of the University of Pennsylvania in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy 2011 Supervisor of Dissertation Co-Supervisor of Dissertation Signature ____________ Signature ____________ Junhyong Kim, Ph.D. Jim Eberwine, Ph.D. Graduate Group Chairperson Signature_______________ Doris Wagner, Ph.D. Dissertation Committee Nancy Bonini, Ph.D., Professor of Biology, (Dissertation Committee chair) Maja Bucan, Ph.D., Professor of Genetics Dustin Brisson, Ph.D., Assistant Professor of Biology Marc Schmidt, Ph.D., Associate Professor of Biology EVOLUTION OF MOLECULAR FUNCTION IN MAMMALIAN NEURONS COPYRIGHT Chantal Francis 2011 DEDICATION I would like to dedicate this dissertation to my family for all their love and support. Especially to my beloved husband Peter. iii ACKNOWLEDGEMENTS There are no shortcuts for an achievement. None of this work would have been possible without the intellectual and mental support of many, many people to whom I am deeply grateful. I would like to acknowledge the members of my thesis committee: Dr. Nancy Bonini, Dr. Maja Bucan, Dr. Dustin Brisson, and Dr. Marc Schmidt for great advice and constructive criticism throughout these years. Their advice and suggestions helped me to refine and achieve my thesis goals. I would also like to acknowledge all past and current members of the Kim lab: Dan, Dexter, Fan, Hannah, Hoa, Kathryn, Miler, Mugdha, Sheng, Saurav, Shreedhar, and Stephen. Their different backgrounds and amazing computational skills helped me incredibly and allowed me to move forward in my data analysis. Despite the diversity of their work, all Kim lab members were united by their friendliness. This is so important in making your graduate student life more enjoyable! Dan and Miler were always so friendly and available to help me with my basic programming skills. They both are very organized and such talented teachers. They were so patient with me! From my collaboration with Shreedhar, I also learned many aspects related to computational biology as well as life. Stephen’s contribution, creating an online database, was extremely valuable to my in situ project. His extensive computer skills and wise advice helped me avoid lots of computer crashes and data loss. I am grateful to Kathleen (an “unofficial” Kim lab member) for her great advice on surviving the pressures of dissertation writing and for making sure I had something to eat for my late nights in the lab. The hub of talent and kindness from the Kim lab is but a small reflection of who Junhyong is. My first interaction with Junhyong was as a technician and throughout the years the more I interacted with him the deeper my admiration became. It is sincerely impossible for me to describe in few words all my gratitude for such an empathic boss, knowledgeable teacher and advisor, and considerate human being. One of the greatest things that happened to me as a graduate student was to perform my thesis work in a partnership with Dr. Jim Eberwine. This collaboration quickly became the keystone of my thesis thanks to Jim’s generosity and welcome in his lab. Jim was an incredible co-mentor from whom I have learned to be more confident in my thoughts and to think more as a scientist. Beside his extreme talent and passion for iv science, Jim was also very understanding and supportive of my family obligations. For this, I am sincerely thankful. Working in Jim’s lab not only allowed me to learn many new technical skills but also allowed me the unique opportunity to meet and interact with his lab members. I would like to acknowledge Ditte, Jackie, Jai, Jae-Hee, Jenn, Jeanine, Kevin, Pete, Sean, Terri, Tiina and Thom. All of them helped in some way ranging from teaching me single cell dissection, in situ techniques and the beauty of microscopy to even providing advice on my writing. Beside their technical assistance, they have been great co-workers reviving the bench work area with fun discussions about food, American sports games, which was a big novelty for me that I am still learning a lot about, or Nobel prizes. I have to acknowledge that none of my experiments would have been feasible without the thousands of primary neuron cultures that Margie prepared for me. It was always a pleasure going to Margie’s lab to pick up my samples and to see her bright smile that cheered up my day. I am also grateful to the very talented students Irmina, Emily and John who helped me on the immense and tedious tasks of the in situ project during their internship in Jim’s lab. I must also thank Dr. Brian Gregory who opened his lab to me, and walked me through all of the steps in the library preparation of next generation sequencing. Being a TA during the first two years of Graduate school was tough but such a great learning experience. It made me realize how challenging it is to convey your thoughts and understanding to others and that teaching a subject to others is far different from understanding it yourself. I am grateful to Dr. Linda Robinson for training me and for giving me great tips about speaking in public and dealing with delicate situation with students. The underlying force behind my choice to enter graduate school comes from Paul Sniegowski’s lab. I came to the U.S. with a master’s degree and the thought that I was done as far as my education. Joining Paul’s lab revived my passion for science and pushed my ambition further. Paul was an amazing teacher and his former graduate student’s, Heidi and Helen, enthusiasm and persistence in their work was a key motivation for me. My graduate student years were enormously enriched in basic science, technical skills and wonderful discussions with very bright people…it was also full of ups and downs. Junhyong once said: “Graduate school is like a marathon”. It is all about v endurance, learning from the down side and gaining even more force from it to pursue your goals to the end, even though science never ends. If I was able to put this dissertation together and stay physically and mentally sane, it is only because of the support of my friends, family and beloved son and husband. To Helen, Maurits, Vero, Paul, Sophie, and Hélène, meeting you during grad school was such a breath of fresh air! To Danielle & Amr, our friendship and your advice were so valuable to me throughout the toughest moments of my grad school.