Dendritic Spine Abnormalities In A Mouse Model Of Fragile X Syndrome

60 Pages·2015·1.31 MB·English

UC Santa Cruz
UC Santa Cruz Electronic Theses and Dissertations
Title
Dendritic Spine Abnormalities In A Mouse Model Of Fragile X Syndrome
Permalink
https://escholarship.org/uc/item/4z72f1hw
Author
Aharon, Adam
Publication Date
2015
Copyright Information
This work is made available under the terms of a Creative Commons Attribution-
NoDerivatives License, availalbe at https://creativecommons.org/licenses/by-nd/4.0/

Peer reviewed|Thesis/dissertation
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University of California
UIVERSITY OF CALIFORNIA
SANTA CRUZ

DENDRITIC SPINE ABNORMALITIES IN A MOUSE MODEL OF
FRAGILE X SYNDROME

A thesis submitted in partial satisfaction
of the requirements for the degree of

MASTERS OF ARTS
in
MOLECULAR, CELL AND DEVELOPMENTAL BIOLOGY
by
Adam Aharon
December 2015

The Thesis of Adam Aharon
is approved:

__________________________
Professor Yi Zuo, Chair

__________________________
Professor Rohinton Kamakaka

__________________________
Professor David A. Feldheim
____________________________
Tyrus Miller
Vice Provost and Dean of Graduate Studies
Copyright © by
Adam Aharon
2015
Table of Contents
List of Figures……………………………………………………………………..…vi
Abstract……………………………………………………………………………..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
iii
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
iv
Chapter 4: Discussion………………………………………………………………31
Chapter 5: Conclusion……………………………………………………………...35
References…………………………………………………………………………...36

v
List of Figures
Figure 1……………………………………………………………………………...41
Figure 2……………………………………………………………………………...42
Figure 3……………………………………………………………………………...43
Figure 4……………………………………………………………………………...44
Figure 5……………………………………………………………………………...45
Figure 6……………………………………………………………………………...46
Figure 7……………………………………………………………………………...47
Figure 8……………………………………………………………………………...48
Table 1……………………………………………………………………………….49

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Abstract
Adam Aharon
Dendritic spine abnormalities in a mouse model of Fragile X syndrome
Fragile X syndrome (FXS) is the most common form of genetically inherited
mental retardation and although it has been investigated for over 20 years, how
cognitive function is specifically disrupted remains unknown. One of the most
consistent neuronal phenotypes observed in FXS is increased density of dendritic
spines, the protrusions that form postsynaptic components of excitatory synapses.
This study further investigates spine abnormalities of the mouse model of FXS in
different neuronal compartments, cell types, and cortical regions of wild type and
mutant mice, as well as heterozygotes. Increased spine density was identified in
mutant mice specifically on apical dendrites of layer 5 neurons. This phenotype only
manifests during adulthood and the effect is consistent across multiple sensory
regions of the cortex. However, effects on spine density differed between neuronal
cell types. These findings identify previously unobserved region, cell type, and cell
compartment-specific effects in the mouse model of FXS.

vii
To my family and friends
for all of their support and encouragement

viii
Acknowledgments
I would like to first thank my advisor and mentor Dr. Yi Zuo for all of her
teaching, support, encouragement and enthusiasm. Her passion and work ethic in the
field of neuroscience is unmatched and I feel extremely fortunate to have had the
opportunity to learn and grow under her supervision and support. She has given me
wonderful opportunities that I would never have had otherwise, and I feel eternally
indebted to her for the lessons she bestowed on me in the field of scientific research
as well as in life.
I would also like to thank my committee members Rohinton Kamakaka and
David Feldheim for their helpful advice and encouragement. Many professors have
been very influential to me during my time at UCSC, and working closely with them
has greatly taught me what it means to be an effective teacher and mentor. These
include, but are not limited to, Susan Strome, Rohinton Kamakaka, Jeremy Lee, Bill
Saxton, and Giulia Ruben.
I would like to thank all members of the Zuo lab that I have had the pleasure
to work with over the years. In particular I would like to thank Caitlin Moyer for all
of her encouragement, support, friendship and helpful criticisms of my work and this
thesis. I would also like to thank Eric Chen and Jenifer Hodges for all of their help
and friendship, I could not have asked for better lab mates. In addition I would like to
thank James Perna for being a constant source of entertaining distraction and good
thoughtful and engaging conversation, as well as Anthony Gilmore for his friendship
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