The Pennsylvania State University

The Graduate School

College of Medicine

INVESTIGATING THE INTERPLAY OF INTRINSIC TO EXTRINSIC FACTORS

INFLUENCING AMYOTROPHIC LATERAL SCLEROSIS DISEASE PROGRESSION

A Dissertation in

Molecular Medicine

Xiaowei William Su

Submitted in Partial Fulfillment of the Requirements for the Degree of

Doctor of Philosophy

August 2014 ii

The dissertation of Xiaowei William Su was reviewed and approved* by the following:

James R. Connor University Distinguished Professor Vice Chair of Neurosurgery Dissertation Advisor Chair of Committee

Xuemei Huang Vice Chair of Neurology

Zachary Simmons Professor of Neurology

Hanspeter Waldner Assistant Professor of Microbiology and Immunology

Charles H. Lang Professor of Cellular and Molecular Physiology Co-Chair of Molecular Medicine Graduate Program

*Signatures are on file in the Graduate School.

iii

ABSTRACT

Amyotrophic lateral sclerosis (ALS) is a relentlessly progressive, neurodegenerative disorder primarily affecting lower motor neurons in the spinal cord and brainstem, and upper motor neurons in the motor cortex. The disorder has a worldwide incidence of 1.7-2.3 per

100,000 population per year, and a prevalence of 4-6 per 100,000 population. The average age of symptom onset is 62 years, the median survival time is 28 months from onset, and the 4-year survival rate is 40%. The disease causes paralysis of the voluntary muscles. ALS is uniformly fatal, and death results from respiratory failure. Riluzole is the only compound approved by the

FDA to treat ALS. It extends lifespan by an average of 1-2 months. All of the more than 50 other compounds tested in clinical trials have failed to demonstrate any benefits for patients. The etiology of ALS, especially sporadic ALS (SALS), which comprises approximately 90% of total cases, remains largely unknown. Improved patient outcomes depend on understanding the pathways responsible for disease, and uncovering novel targets for future therapies.

The pathogenesis of ALS begins before a diagnosis can be made in the clinic. Significant motor neuron loss occurs prior to the discernable onset of symptoms. Ideally, research would be able to pinpoint the precise temporal and spatial progression of pathophysiological processes underlying ALS, close to their initiating events. However, this is difficult at present. Many experimental models of ALS exist, which should theoretically permit detailed investigation of

ALS pathogenesis. However, other than riluzole, no compound with efficacy in pre-clinical models has had measurable clinical benefits, highlighting differences between animal and human biology as well as the importance of translational research. Given the difficulties in analyzing the events precipitating ALS, analysis of the ongoing processes influencing disease progression becomes an important strategy to elucidate disease mechanisms and pinpoint novel drug targets. iv

This dissertation investigated factors influencing ALS disease progression, using the framework that the interplay of a range of extrinsic and intrinsic factors determine phenotypes.

Intrinsic factors, such as a patient’s genetic makeup, remain relatively stable throughout life.

Extrinsic factors, such as drug therapies, vary with time and environment. Intermediate factors, such as proteins that can function as biomarkers, depend on and reflect the individual’s innate genetic and metabolic profile as well as the environment. The interplay of these factors help determine the quality of life and disease duration of a patient with ALS.

Our analysis of intrinsic, genetic factors focused on the H63D polymorphism in the HFE iron regulatory gene. This polymorphism was previously associated with neurodegenerative disorders, including ALS. It is also believed to increase ALS risk. Our results suggest that homozygosity f