Genetic architecture of neurogenesis in the adult mouse forebrain : insights from quantitative trait locus analyses

ii Preface . iv Table of Contents . vi List of Tables . xi List of Figures . xii List of Abbreviations . xiv Acknowledgements . xvii Dedication . xix Chapter 1: Introduction . 1 1.1 Neurogenesis in the adult mammalian brain . 1 1.1.1 Historical overview of adult neurogenesis . 1 1.1.2 Major sites of adult neurogenesis . 3 1.1.2.1 Subgranular zone (SGZ) of dentate gyrus . 3 1.1.2.2 Subventricular zone (SVZ) and rostral migratory stream (RMS) . 5 1.1.3 Functional implications of adult neurogenesis . 9 1.1.3.1 Functional relevance of adult hippocampal neurogenesis . 9 1.1.3.2 Functional relevance of adult OB neurogenesis . 12 1.1.4 Association with pathological conditions . 14 1.2 Regulation of adult neurogenesis . 17 1.2.1 Extrinsic factors . 17 1.2.1.1 Environment . 17 vii 1.2.1.2 Neuropeptides and hormones . 19 1.2.1.3 Growth and neurotrophic factors . 22 1.2.2 Cell intrinsic factors . 24 1.2.2.1 Genetic background . 24 1.2.2.2 Cell cycle regulators and transcription factors . 25 1.3 Approaches for the study of genetic architecture underlying adult neurogenesis . 27 1.3.1 In vitro cell culture systems . 28 1.3.2 In vivo approaches using genetically modified mice . 29 1.3.3 Genome-wide approach . 33 1.3.3.1 Quantitative trait locus analysis and gene discovery . 34 1.3.3.2 Recombinant inbred mice . 37 1.4 Research objectives . 40 Chapter 2: Effect of genetic background on adult neural progenitor cell proliferation: an opportunity to discover genetic modifiers . 42 2.1 Introduction . 42 2.2 Materials and methods . 43 2.2.1 Animals . 43 2.2.2 BrdU labeling and detection . 44 2.2.3 Quantification . 45 2.2.4 Cumulative BrdU labeling for cell cycle analysis . 46 2.2. 5 3-Dimensional reconstruction of the RMS and its total cell population . 47 2.2. 6 Quantitative trait locus analysis . 47 2.2. 7 Statistical analysis . 48 viii 2.3 Results . 48 2.3.1 Strain-specific differences in the number of proliferative cells in the adult RMS . 48 2.3.2 Shape, orientation, and size of the RMS in different inbred mouse strains . 52 2.3.3 Cell cycle lengths of adult neural progenitor cells from different mouse strains . 53 2.3.4 Strain comparison in cell proliferation across different ages . 56 2.3. 5 Heritability of neural progenitor cell proliferation and genotype-phenotype association . 61 2.4 Discussion . 63 Chapter 3: Identification of quantitative trait loci and candidate genes that modulate adult neural progenitor cell proliferation . 66 3.1 Introduction . 66 3.2 Materials and methods . 67 3.2.1 Animals . 67 3.2.2 Anti-BrdU immunohistochemistry and quantification . 67 3.2.3 Quantitative trait locus analysis . 68 3.2.4 Candidate gene analysis . 69 3.2. 5 Statistical analysis . 70 3.3 Results . 70 3.3.1 Two panels of recombinant inbred strains exhibited wide differences in RMS cell proliferation . 70 3.3.2 Significant QTLs associated with the inter-strain differences in RMS cell proliferation . 76 3.3.3 Cell proliferation in the SGZ is regulated by a different set of QTLs . 84 ix 3.3.4 Mapped loci harbor genes that may serve as modulators of NPC proliferation . 86 3.4 Discussion . 96 Chapter 4: Investigation of the galanin receptor 2 (Galr2) as a modulator of neural progenitor cell proliferation . 100 4.1 Introduction . 100 4.2 Materials and methods . 102 4.2.1 Animals . 102 4.2.2 Fluorescent immunohistochemistry . 103 4.2.3 SVZ progenitor cell culturing and siRNA transfection . 103 4.2.4 Galr2 overexpression . 104 4.2. 5 BrdU labeling and quantification . 105 4.2. 6 Statistical analysis . 107 4.3 Results . 107 4.3.1 Galr2 is expressed in adult neurogenic sites and NPCs .