Uiversity of California Santa Cruz Dendritic Spine Abnormalities in a Mouse Model of Fragile X Syndrome

........................................................................................vii Dedication......................................................................................viii Acknowledgements............................................................................ix Chapter 1: Introduction.......................................................................1 1.1 Background........................................................................1 1.1.1 Fragile X syndrome...................................................1 1.1.2 X chromosome inactivation..........................................3 1.1.3 Fragile X mental retardation protein.................................4 1.1.4 Dendritic spines.......................................................5 1.1.5 Dendritic compartments..............................................6 1.1.6 Neuronal circuits......................................................8 1.2 Research objectives...............................................................9 1.3 Motivation........................................................................11 Chapter 2: Methods...........................................................................12 2.1 Animals.............................................................................12 2.2 Genotyping........................................................................13 2.3 Tissue prep and immunohistochemistry.....................................13 iv 2.4 Cell counts.........................................................................15 2.5 Cell tracing........................................................................16 2.6 Data analysis......................................................................17 Chapter 3: Results.............................................................................19 3.1 FMRP expression reduced in KO mice......................................19 3.2 Spine density is differentially altered between apical and basal dendrites of layer 5 neurons of Fmr1 KO mice.................................20 3.3 Dendritic spine alterations in somatosensory cortex of Fmr1 KO mice are consistent across multiple cortical sensory regions.......................22 3.4 Dendritic spine density is altered in adult but not adolescent Fmr1 KO mice......................................................................................24 3.5 Layer II/III pyramidal cells of Fmr1 KO mice do not display increased spine density..............................................................26 3.6 Spine density is increased in both apical and basal dendrites of CA1 hippocampal neurons in Fmr1 KO mice.........................................27 3.7 Heterozygous females display spine density similar to KOs in L5 neurons of somatosensory cortices................................................28 3.8 Heterozygous females display spine density similar to WTs in CA1 neurons of hippocampus............................................................30 v Chapter 4: Discussion........................................................................31 Chapter 5: Conclusion........................................................................35 References.......................................................................................36