Deep Sequencing and Annotation of the Trichoplax Adhaerens Mrna
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Deep Sequencing and Annotation of the Trichoplax adhaerens mRNA Transcriptome Identifies Novel Genes and a Rich Repertoire of Neural Signaling Machinery, Providing Insight into Nervous System Evolution by Yuen Yan Wong A thesis submitted in conformity with the requirements for the degree of Master of Science Department of Cell and Systems Biology University of Toronto © Copyright by Yuen Yan Wong 2018 Deep Sequencing and Annotation of the Trichoplax adhaerens mRNA Transcriptome Identifies Novel Genes and a Rich Repertoire of Neural Signaling Machinery, Providing Insight into Nervous System Evolution Yuen Yan Wong Master of Science Department of Cell and Systems Biology University of Toronto 2018 Abstract Trichoplax adhaerens is an early-diverging animal capable of motile behavior such as feeding, chemotaxis, and phototaxis, despite lacking synaptically-connected neurons and muscles. Our lab has produced a high-quality T. adhaerens transcriptome in which ~85% of the assembled genes are complete protein-coding sequences, with 2,483 newly-identified genes missed in the genome sequencing effort. One objective of this research was to identify genes involved in neural signaling. Using in silico prediction algorithms we identified an array of neuropeptide genes, GPCRs, ion channels, and synaptic scaffolding and signaling proteins. We also discovered a previously unknown group of presynaptic Rab3-Interacting Molecule (RIM) homologues in the animal phylogeny, absent in humans but present in many invertebrates. Our work sets the stage for future studies aimed at understanding the concurrent evolution of metazoan cell types, and their ability to communicate with each other through various forms of cell signaling including electrochemical signaling in the nervous system. ii Acknowledgments I would first like to thank my supervisor, Dr. Adriano Senatore, for his mentorship and guidance throughout the past two years of my Master’s studies, and his assistance in helping me prepare my thesis. Thank you Dr. Senatore for giving me the opportunity to further explore my research interests and to be able to push myself beyond my limits. Besides my advisor, I would like to thank my committee members, Dr. Mary Cheng and Dr. Robert Ness, for their guidance and support. I would like to especially thank Brian Novogradac. As a beginner in bioinformatics, I am grateful for all his great help and technical support he had been providing me throughout the two years. Next, I express my sincere gratitude to my wonderful colleagues. Thank you Sally and Alicia. Thank you so much for always being there for me, for all the sleepless nights and blood, sweat and tears we experience together while working for deadlines, and every time we celebrate our minor successes and happiness with lots of food and coffee breaks. Thank you for always being supportive and loving, and for creating all these wonderful memory with me which I will cherish for life. Thank you, Dr. Marcia Roy, for your kind support and guidance. Thank you so much for helping me with the postsynaptic proteins analysis, and in particular, thank you very much for showing me how to always love science and research! I really appreciate all of our exciting and inspiring conversations. Last, but not least, I would like to thank my family and friends for all the moral support they have given me all along. I would especially like to deliver my enormous gratitude to my parents and my siblings, for always being extremely supportive and understanding, and for always making sure I have everything I need. I am grateful to have you all by my side. iii Table of Contents ACKNOWLEDGMENTS ........................................................................................................................................... III TABLE OF CONTENTS ............................................................................................................................................ IV LIST OF FIGURES ................................................................................................................................................... VI LIST OF TABLES .................................................................................................................................................... VII LIST OF APPENDICES ........................................................................................................................................... VIII LIST OF ABBREVIATIONS/TERMINOLOGIES ........................................................................................................... IX CHAPTER 1 ............................................................................................................................................................. 1 INTRODUCTION: TRICHOPLAX ADHAERENS AS A MODEL ORGANISM FOR NEUROSCIENCE RESEARCH ........ 1 1.1 WHAT IS A NERVOUS SYSTEM? .................................................................................................................... 1 1.2 THE ANIMAL PHYLOGENY AND NERVOUS SYSTEM EVOLUTION ............................................................................. 1 1.2.1 The Animal Phylogeny ..................................................................................................................... 1 1.2.2 Controversies about the Origin of the Nervous System ..................................................................... 2 1.3 TRICHOPLAX ADHAERENS ............................................................................................................................ 3 1.3.1 What is it? ....................................................................................................................................... 3 1.3.2 Taking a Transcriptomics Approach ................................................................................................. 4 CHAPTER 2 TRANSCRIPTOME ANALYSIS OF TRICHOPLAX ADHAERENS REFLECTS A DIGESTIVE EPITHELIUM WITH CELLULAR COORDINATION AND AN ARRAY OF GENES INVOLVED IN NEURAL SIGNALING ..................................... 6 TRANSCRIPTOME ANALYSIS OF TRICHOPLAX ADHAERENS REFLECTS A DIGESTIVE EPITHELIUM WITH CELLULAR COORDINATION AND AN ARRAY OF GENES INVOLVED IN NEURAL SIGNALING ..................................... 6 2.1 METHODS............................................................................................................................................... 6 2.1.1 RNA Isolation and Illumina Sequencing ............................................................................................ 6 2.1.2 Transcriptome Production ................................................................................................................ 6 2.1.3 Transcriptome Metrics and Gene Ontology ...................................................................................... 8 2.1.4 Comparison against the Published Genome...................................................................................... 9 2.1.5 Extended and Full T. adhaerens Predicted Proteome ...................................................................... 10 2.1.6 Secretome Production.................................................................................................................... 10 2.1.7 Regulatory/Neuro-Peptide Prediction............................................................................................. 11 2.1.8 GPCRome Production and Classification Identification .................................................................... 12 2.1.9 Protein Sequence Annotations ....................................................................................................... 12 2.1.10 Cross-Phyla Domain Analysis ..................................................................................................... 13 2.2 RESULTS ............................................................................................................................................... 15 2.2.1 Transcriptome Metrics ................................................................................................................... 15 2.2.2 Gene Ontology .............................................................................................................................. 15 2.2.3 Comparison against Genome ......................................................................................................... 17 2.2.4 The Secretome ............................................................................................................................... 21 2.2.5 Regulatory/Neuro- Peptides........................................................................................................... 21 2.2.6 Neurotransmitter Biosynthesis and Degradation Pathways ............................................................ 23 2.2.7 Receptors and the GPCRome .......................................................................................................... 24 2.2.8 Channel Protein Homologues ......................................................................................................... 26 2.2.9 Pre-/Post- Synaptic Scaffolding and Signaling Protein Homologues Cross-Phyla Domain Analysis .... 27 2.2.10 Cross-Phyla Protein-Protein Interaction-Related Domain Counts Analysis ................................... 30 2.3 DISCUSSIONS ......................................................................................................................................... 30 2.3.1 A High-Quality T. adhaerens Gene Set 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