The synergistic effects of gastrointestinal inflammation and the G2019S Lrrk2 mutation on Parkinson’s disease associated phenotypes as defined by RNA-sequence analysis Open Access

Abstract

Parkinson’s disease (PD) is the second most common neurodegenerative disease and is further classified as a progressive movement disorder. Specific to its symptoms, PD primarily affects mobility and can lead to constant body tremors, muscle rigidity, and slowness of movement. Certain non-motor symptoms can also become apparent such as cognitive dysfunction, fatigue, and gastrointestinal disturbances. With these symptoms aside, the pathology of PD is primarily due to the degeneration of dopaminergic neurons within the substantia nigra although Lewy body accumulation and inflammation are also involved. Furthermore, certain risk factors such as increasing age and numerous other environmental and genetic factors are all implicated in PD development and therefore affect an individual’s susceptibility for developing PD. However, even with a plethora of existing knowledge surrounding PD, the ability of scientists to discern the origin of and reasons for PD development associated with each affected individual is still lacking. As a result, this study sought to better understand both environmental and genetic factors involved in PD development by focusing on the potential synergistic effects of the G2019S Lrrk2 mutation (one of the most prevalent familial PD mutations) and gut inflammation induced by dextran sodium sulfate (DSS). More specifically, substantia nigra samples from 59 total mice were collected with 41 mice having been previously exposed to a 30-day chronic DSS-induced colitis paradigm and the remaining 18 mice having been treated with water to serve as controls. The statistical program Rstudio was then used to identify differential gene expression by making comparisons between both genotype (B6, WTOE, G2019S) and treatment type (DSS-treated vs water-treated). Differences in gene expression were then assessed by either one-way analysis of variance or a student t-test to verify significance. Overall, these results suggest that genes associated with various cellular processes such as neuroprotection, inflammation, and saliva production may all experience changes in expression as a result of PD associated phenotypes. Therefore, with these findings we hope to contribute to future research surrounding the signaling pathways involved in PD development in order to ultimately aid in the identification and development of potential therapeutics to combat this neurodegenerative disease.

Table of Contents

Introduction .............................................................................................................. 1

Incidence .................................................................................................................. 1

Motor and Non-motor symptoms ................................................................................ 2

Pathology ................................................................................................................. 3

Risk Factors .............................................................................................................. 8

Project Goal and Hypothesis ..................................................................................... 12

Materials and Methods ............................................................................................. 13

Mouse Models ......................................................................................................... 13

Chronic DSS-Induced Colitis Paradigm ...................................................................... 14

RNA Sequence Analysis ............................................................................................ 15

Results .................................................................................................................... 19

Confirmation of Lrrk2 expression using RNA Sequence Analysis Technique .................. 19

Differentially Expressed Genes – Analyses 1-4 ........................................................... 19

Differentially Expressed Genes – Analyses 5-7 ........................................................... 20

Discussion ............................................................................................................... 22

Conclusion .............................................................................................................. 36

Figures and Graphs .................................................................................................. 37

Table 1 – Transgenic Mice Models ............................................................................. 37

Figure 1 – Visualization of Chronic DSS-Induced Colitis Paradigm .............................. 38

Figure 2 – RNA Sequence Experimental Workflow ...................................................... 39

Table 2 – Categorical Organization of Mice subjects ................................................... 40

Figure 3 – Lrrk2 Expression levels across genotypes ................................................... 41

Figure 4 – Smgc Expression levels across genotypes ................................................... 42

Figure 5 – Muc19 Expression levels across genotypes ................................................. 43

Figure 6 – Sycp1 Expression levels across genotypes ................................................... 44

Figure 7 – Gm15382 Expression levels across genotypes ............................................. 45

Figure 8 – DSS-treated v Water-treated – WTOE mice differential gene expression ....... 46

Figure 9 – DSS-treated vs Water-treated – G2019S mice differential gene expression .... 47

Works Cited ............................................................................................................. 48

About this Honors Thesis

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School	Emory College
Department	Neuroscience and Behavioral Biology
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Biology, Neuroscience
Keyword	RNA-Seq Parkinson's Disease LRRK2
Committee Chair / Thesis Advisor	William Caudle, Emory University
Committee Members	Kristen Frenzel, Emory University Malu Tansey, Emory University Mary Herrick, Emory University

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