The impact of Charcot-Marie-Tooth 4B3 disease mutation in SBF1 on the regulation of MTMR2 during autophagy
| Author(s) | Friel, Olivia J. | |
| Date Accessioned | 2025-05-27T18:17:41Z | |
| Date Available | 2025-05-27T18:17:41Z | |
| Publication Date | 2025 | |
| SWORD Update | 2025-05-12T04:03:28Z | |
| Abstract | Charcot Marie Tooth (CMT) disease is characterized as a group of hereditary peripheral neuropathies that can manifest as either demyelinating disorders or axonopathies. CMT4B3 is a mixed demyelinating and axonal polyneuropathy with high variability in disease progression and motor phenotype. CMT4B3 is characterized by mutations in the Set Binding Factor 1 (SBF1) gene which encodes Myotubularin Related Protein 5 (MTMR5), a catalytically inactive pseudophosphatase. SBF1 directly interacts with MTMR2, a phosphoinositide phosphatase, in the cytosol and upregulates its catalytic activity. MTMR2 dephosphorylates phosphoinositides which regulate the vesicular trafficking during Schwann cell and axonal formation. The phosphoinositide targets for MTMR2 are involved in autophagosome formation and lysosomal degradation. Loss of this regulation results in disrupted motor neuron axon formation as well as uncontrolled organization of myelin around motor neuron axons. Previous studies indicate when SBF1 functionality is diminished autophagy is increased. The hypothesis is that muta-tions in SBF1 impact the regulation of phosphatase activity of MTMR2 and downstream effects of this result in loss of function in motor neurons in CMT patients. ☐ Patient-derived fibroblast cells can be converted to motor neurons to model diseases bypassing the use of embryonic stem cells (ESCs) through a process known as direct reprogramming. Cell lines isolated from a CMT4B3 patient, with a compound heterozygous mutation from each parent, and their parents were used to characterize the disease of this specific patient as well as in the spinal cord tissue of Sbf1 knockout (Sbf1-/-) mice. ☐ Transcript and protein levels for SBF1, SBF2, MTMR2, and autophagy factors were measured using quantitative RT-PCR and immunoblotting. Transcript and protein levels for SBF1 are reduced in knockout mouse spinal cord and unchanged in patient fibroblast samples. Autophagy protein levels are relatively unchanged in mouse spinal cord tissue, however, there appear to be sex differences between male and female mice. A direct reprogramming protocol for converting patient fibroblast cells to motor neurons was designed and optimized and future research can be used to measure and validate autophagy in these cells. | |
| Advisor | Butchbach, Matthew E. R. | |
| Degree | M.S. | |
| Department | University of Delaware, Department of Biological Sciences | |
| Unique Identifier | 1525425098 | |
| URL | https://udspace.udel.edu/handle/19716/36197 | |
| Language | en | |
| Publisher | University of Delaware | |
| URI | https://www.proquest.com/pqdtlocal1006271/dissertations-theses/impact-charcot-marie-tooth-4b3-disease-mutation/docview/3202787572/sem-2?accountid=10457 | |
| Keywords | Charcot Marie Tooth | |
| Keywords | Set Binding Factor 1 | |
| Keywords | Cell lines | |
| Keywords | Catalytic activity | |
| Keywords | MTMR2 dephosphorylates | |
| Title | The impact of Charcot-Marie-Tooth 4B3 disease mutation in SBF1 on the regulation of MTMR2 during autophagy | |
| Type | Thesis |