by Yan Hiu Mei, Carol. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 114-126). / Abstracts in English and Chinese. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgements --- p.iv / Table of Contents --- p.v / List of Tables --- p.viii / List of Figures --- p.ix / Abbreviations --- p.xii / Chapter CHAPTER 1 --- TRANSGENIC TECHNOLOGY --- p.1 / Chapter 1.1 --- Transgenesis in animals --- p.1 / Chapter 1.2 --- Transgenic fish in toxicology --- p.4 / Chapter 1.2.1 --- Aquatic metal toxicity --- p.4 / Chapter 1.2.2 --- Environmental monitoring of aquatic metal toxicity --- p.5 / Chapter 1.2.3 --- Biomarkers --- p.6 / Chapter 1.3 --- Transgenics in aquaculture --- p.9 / Chapter 1.3.1 --- Revolution is needed in aquaculture --- p.9 / Chapter 1.3.2 --- Aquaculture potential of tilapia in China --- p.10 / Chapter 1.3.3 --- Endocrinology for fish growth --- p.12 / Chapter 1.3.4 --- Growth promotion by exogenous growth hormone in tilapia --- p.14 / Chapter 1.3.5 --- Accelerated growth in transgenic fish --- p.15 / Chapter 1.4 --- General principle in transgenic fish production --- p.16 / Chapter 1.5 --- Project aim --- p.22 / Chapter CHAPTER 2 --- ISOLATION AND CHARACTERIZATION OF ZEBRAFISH METALLOTHIONEIN GENE PROMOTER --- p.23 / Chapter 2.1 --- Introduction --- p.23 / Chapter 2.1.1 --- Metallothionein --- p.23 / Chapter 2.1.2 --- Biological functions --- p.24 / Chapter 2.1.3 --- Metallothionein gene regulations --- p.25 / Chapter 2.1.4 --- Metallothionein as biomarker for metal pollution --- p.26 / Chapter 2.2 --- Materials and methods --- p.28 / Chapter 2.2.1 --- General molecular biology techniques --- p.28 / Chapter 2.2.2 --- Sequences of PCR primers used --- p.31 / Chapter 2.2.3 --- Cloning zebrafish MT gene 5-flanking region --- p.31 / Chapter 2.2.4 --- Cloning zebrafish MT gene --- p.32 / Chapter 2.2.5 --- Cloning full length zMT gene --- p.33 / Chapter 2.2.6 --- Cell culture --- p.35 / Chapter 2.2.7 --- Transient transfection assay --- p.37 / Chapter 2.2.8 --- Electrophoretic mobility shift assay --- p.39 / Chapter 2.3 --- Results --- p.42 / Chapter 2.3.1 --- Zebrafish metallothionein gene --- p.42 / Chapter 2.3.2 --- Deletion analysis of zMT promoter by transient transfection assay --- p.48 / Chapter 2.3.3 --- Functional characterization of zebrafish metallothionein promoter --- p.57 / Chapter 2.4 --- Discussions --- p.61 / Chapter 2.4.1 --- Zebrafish MT gene --- p.61 / Chapter 2.4.2 --- Functional characterization of zebrafish MT promoter --- p.61 / Chapter CHAPTER 3 --- PREPARATION OF GENE CONSTRUCTS FOR TRANSFER IN ZEBRAFISH --- p.65 / Chapter 3.1 --- Introduction --- p.65 / Chapter 3.1.1 --- Zebrafish as model in toxicological studies --- p.65 / Chapter 3.1.2 --- Reporter gene system --- p.66 / Chapter 3.1.3 --- Transgenic reporter fish --- p.68 / Chapter 3.1.4 --- Gene transfer by electroporation in zebrafish --- p.68 / Chapter 3.1.5 --- Objective --- p.69 / Chapter 3.2 --- Materials and methods --- p.70 / Chapter 3.2.1 --- Design of gene constructs for ectopic expression in zebrafish --- p.70 / Chapter 3.2.2 --- Testing electroporation conditions for zebrafish --- p.72 / Chapter 3.3 --- Results --- p.73 / Chapter 3.4 --- Discussions --- p.76 / Chapter 3.4.1 --- Engineering gene constructs --- p.76 / Chapter 3.4.2 --- Applications of transgenic zebrafish --- p.79 / Chapter CHAPTER 4 --- GENE TRANSFER EXPERIMENTS ON TILAPIA --- p.82 / Chapter 4.1 --- Introduction --- p.82 / Chapter 4.2 --- Materials and methods --- p.85 / Chapter 4.2.1 --- Isolation of O. aureus growth hormone --- p.85 / Chapter 4.2.2 --- Engineering gene constructs for ectopic expression in tilapia --- p.86 / Chapter 4.2.3 --- Gene transfer in tilapia --- p.87 / Chapter 4.2.4 --- Screening transgenic tilapia --- p.89 / Chapter 4.3 --- Results --- p.91 / Chapter 4.3.1 --- Tilapia growth hormone --- p.91 / Chapter 4.3.2 --- Gene constructs for ectopic expression in tilapia --- p.94 / Chapter 4.3.3 --- Testing electroporation conditions --- p.96 / Chapter 4.3.4 --- PCR screening for transgenic fish --- p.97 / Chapter 4.4 --- Discussions --- p.101 / Chapter 4.4.1 --- Tilapia growth hormone --- p.101 / Chapter 4.4.2 --- Electroporation experiments on of tilapia eggs --- p.101 / Chapter 4.4.3 --- Improvements on gene construct design for tilapia --- p.104 / Chapter 4.4.4 --- Ethical and safety considerations --- p.106 / Chapter CHAPTER 5 --- REFERENCES --- p.114 / APPENDIX --- p.127

Awakening of zygotic transcription in animal embryos relies on maternal pioneer transcription factors. The interplay of global and specific functions of these proteins remains poorly understood. Here, we analyze chromatin accessibility and time-resolved transcription in single and double mutant zebrafish embryos lacking pluripotency factors Pou5f3 and Sox19b. We show that two factors modify chromatin in a largely independent manner. We distinguish four types of direct enhancers by differential requirements for Pou5f3 or Sox19b. We demonstrate that changes in chromatin accessibility of enhancers underlie the changes in zygotic expression repertoire in the double mutants. Pou5f3 or Sox19b promote chromatin accessibility of enhancers linked to the genes involved in gastrulation and ventral fate specification. The genes regulating mesendodermal and dorsal fates are primed for activation independently of Pou5f3 and Sox19b. Strikingly, simultaneous loss of Pou5f3 and Sox19b leads to premature expression of genes, involved in regulation of organogenesis and differentiation.