Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease characterized by the deterioration of upper and lower motor neurons in the brain, brain stem, and spinal cord. Multiple missense mutations have been connected to familial ALS, including those in the Matrin-3 protein. Matrin-3 is an RNA and DNA-binding protein encoded by the MATR3 gene. Normally found in the nuclear matrix, Matrin-3 plays several roles vital to RNA metabolism, including splicing, RNA degradation, mRNA transport, mRNA stability, and transcription. Mutations in MATR3 leading to familial ALS include P154S and S85C, but the mechanisms through which these mutations contribute to ALS pathology remain unknown. This makes mouse models particularly useful in elucidating pathology mechanisms, ultimately having the potential to serve as preclinical models for therapeutic drugs. Because of the importance of animal models, we worked to create ALS mouse models for the MATR3 P154S and S85C mutations. We specifically generated two CRISPR/Cas9 mediated knock-in mouse models containing the MATR3 P154S or S85C mutation expressed under the control of the endogenous promoter. Both the homozygous and heterozygous P154S mice developed no physical or motor defects or shortening of lifespan compared to the wildtype mice. They also exhibited no ALS-like pathology in either the muscle or spinal cord up to 24 months. In contrast, the homozygous S85C mice exhibited significant physical and motor differences, including smaller weight, impaired gait, and shortening of lifespan. Some ALS-like pathology was observed in the muscle, but pathology remained limited in the spinal cord of the homozygous mice up to 12 months. In conclusion, our data suggests that the MATR3 P154S mutation alone does not cause ALS in vivo, while the MATR3 S85C mutation induces significant motor deficits, with pathology in the spinal cord potentially beginning at older ages not examined in our study.

For my thesis, I conducted a study on a healthy pediatric cohort to investigate how DNA methylation of genes related to myelin may predict total white matter volume in a healthy pediatric cohort. The relatively new field of neuroimaging epigenetics investigates how methylation of genes in peripheral tissue samples is related to certain structural or functional features of the brain, as measured by neuroimaging data. Research has already demonstrated that methylation of genes in peripheral tissues is related to a variety of brain disorders. We hypothesized that methylation of myelin-related genes as measured in saliva samples would predict total white matter volume in a healthy pediatric cohort. After processing DNA methylation data from saliva samples from participants, multiple linear regressions were ran to determine if DNA methylation of myelin related genes was related to total white matter volume, as measured by data from structural MRIs. Results showed that these genes, which included MOG, MBP, and MYRF, significantly predicted total white matter volume. Two genes that were significant in our results have been previously shown to produce proteins that are essential to the structure of myelin.

Alzheimer’s disease (AD) is an irreversible brain disorder that plagues millions of people with no current cure. Current clinical research is slowly advancing to more definitive treatments in hopes of reducing the effects of progressive cognitive and behavioral decline, but none so far can slow AD’s onset. A brain area known as the nucleus incertus (NI) was recently discovered to potentially impact AD because of its connections to brain targets that degenerate; however, the NI’s role is unknown. This goal of this experiment was to use a transgenic mouse model (APP/PS1) that expresses AD pathology slowly as found in humans, and to test the mice in a variety of cognitive and anxiety assessments. Mice of both sexes and two different ages were used, with the first being young adult before AD pathology manifests (around 3-4 months old), and the second being around the cusp of when AD pathology manifests (late adult, 8-10 months old). The mice were tested in a variety of cognitive tasks that included the novel object recognition (NOR), Morris water maze (MWM), and the object placement (OP), with the latter being the focus of my thesis. Anxiety measures were taken from the open field (OF) and elevated plus maze (EPM) with the visible platform (VP) used to ensure mice could perform on the rigorous MWM task. In the OP, we found an age effect, where the older mice were less likely to explore the moved object during the OP compared to the younger mice; motor ability was unlikely to explain this effect. We did not find any significant age by genotype effects. These findings indicate that cognitive impairment only just started to affect the older cohort, since OP impairment was found on one measure and not another. Other measures currently being quantified will be helpful in understanding this data, and to see whether learning, memory, and anxiety are affected.