Characterization of SERCA function in the hippocampal and prefrontal cortex regions of the brain from C57 and D2 mx mice

Duchenne muscular dystrophy (DMD) is an X-linked muscle wasting disease caused by the loss of the cytoskeletal structural protein, dystrophin. In addition to muscular deficits, approximately 30% of those affected experience cognitive deficits, specifically in learning and memory. Typically known for its role in muscle relaxation and contraction, the sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) is also highly expressed in the brain and therefore is suspected to play a role in the regulation of neuronal Ca2+. Proper Ca2+ homeostasis is one of the most important factors of cognition, and dysfunctional SERCA has been implicated in Alzheimer’s disease pathology. Moreover, recent evidence has shown that the DBA/2J (D2) mdx mouse model of DMD presents with cognitive dysfunction and a shift towards amyloid beta (Ab) production in the hippocampus and prefrontal cortex (PFC). However, this was not observed in the traditional, yet less severe model of DMD, the C57BL/10 (C57) mdx mouse. Furthermore, the exact cellular mechanisms explaining why only young D2 mdx mice (and not C57 mdx mice) present with cognitive dysfunction and Alzheimer’s disease-like pathology in the hippocampal and PFC regions of the brain remains unknown. Therefore, this thesis investigated whether SERCA dysfunction and dysregulation via regulatory proteins neuronatin, presenilin and heat shock protein 70 as well as protein modifications via reactive oxygen/nitrogen species can contribute to these differences. This was done by performing Ca2+ uptake activity assays, western blots, and BACE1 activity assays on homogenates of hippocampus and PFC from C57 and D2 WT and mdx mice. Ca2+ uptake was impaired in mdx mice, more so in the D2 mdx mice, even though SERCA expression was unaltered. Reactive oxygen and nitrogen species (RONS) expression was increased in both mdx mice, while HSP70 content was decreased in D2 mdx mice. Furthermore, the Alzheimer’s disease marker BACE1 was increased in the PFC of mdx mice, along with pTau(Ser202) and a reduction in Ser9 phosphorylated GSK3b. However, no significant changes were seen throughout the hippocampus. Collectively, this thesis presents evidence suggesting impaired SERCA function in both C57 and D2 mdx brain – perhaps due to heightened oxidative/nitrosative stress.

Name thesis:degree_name

M.Sc. Applied Health Sciences

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Faculty of Applied Health Sciences

Department dc:contributor.department

Applied Health Sciences Program

Grantor

Brock University

Year dc:date.issued

2022

Author dc:creator

• Copeland, Emily Nicole

• SERCA
• mdx
• cognition
• Duchenne muscular dystrophy

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/10464/16561

OAI identifier oai:identifier

oai:brocku.scholaris.ca:10464/16561