Dissertation
The role of magnesium homeostasis in embryonic melanocytes and dopamine neurons
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Spring 2020
DOI: 10.17077/etd.005301
Abstract
Magnesium (Mg2+) is the second most abundant intracellular cation and is crucial for proper cell function. Despite this, little regarding intracellular Mg2+ regulation is fully understood. Using the zebrafish model system, we examine the functions of two Mg2+-regulating proteins – Trpm7 and Slc41a1 – in melanocytes and dopaminergic neurons. Our group has previously shown that loss of trpm7 leads to death of embryonic melanocytes. Here, we show that the kinase domain of trpm7 is dispensable for proper melanocyte development, but not divalent ion permeability. In an attempt to further modulate intracellular Mg2+ levels in tprm7 mutants, we targeted Mg2+ exporter slc41a1 for knockdown. Though we saw suppression of the trpm7 mutant melanocyte phenotype in these slc41a1 loss-of-function studies, we determined that the suppression was due to an off-target effect. Due to similarities between family members, we posit that the off-target gene is another slc41a member. Though not confirmed, we therefore have strong evidence that the tprm7 melanocyte death phenotype is due to dysfunction in Mg2+ levels and can be at least partially ameliorated by restoring proper homeostasis.
In terms of human disease, a tentative link exists between Mg2+ deficiency and Parkinson’s Disease. Additionally, SNPs in SLC41A1 are in a linkage disequilibrium locus that is associated with the disease. We hypothesized that loss of Slc41a1 in zebrafish and mouse dopaminergic neuron models would protect against chemically-induced cell death. We found that in the testing paradigms we used, Slc41a1 loss did not protect neurons against cell death.
Finally, in a departure from Mg2+ homeostasis, we sought to find novel anti-convulsant drugs that may be effective in patients with refractory epilepsy. Using zebrafish seizure models, we tested drugs that have already been approved for other indications. We found that metformin, nifedipine, and pyrantel tartrate were effective against chemically-induced seizures, while naltrexone was effective against chemically and genetically induced seizures.
Details
- Title: Subtitle
- The role of magnesium homeostasis in embryonic melanocytes and dopamine neurons
- Creators
- Morgan Sturgeon
- Contributors
- Robert Cornell (Advisor)Alexander Bassuk (Committee Member)Toshihiro Kitamoto (Committee Member)Andrew Frank (Committee Member)Fang Lin (Committee Member)Andrew Russo (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Molecular and Cellular Biology
- Date degree season
- Spring 2020
- DOI
- 10.17077/etd.005301
- Publisher
- University of Iowa
- Number of pages
- xi, 125 pages
- Copyright
- Copyright 2020 Morgan Sturgeon
- Language
- English
- Description illustrations
- illustrations (some color)
- Description bibliographic
- Includes bibliographical references (pages 108-125).
- Public Abstract (ETD)
Magnesium is a little-thought-of ion that is actually very important for human health. Many studies have found that too little magnesium is linked to a variety of different diseases. To better understand why magnesium is so important and how low levels could be causing disease, we chose to study proteins important for controlling magnesium levels in the whole body as well as in an individual cell. One of these proteins, Trpm7, is required for early embryonic development in most animals. However, zebrafish lacking Trpm7 make it through early development, allowing us to study the role of Trpm7 in cell types that arise later. We have previously shown that trpm7 zebrafish mutants lack melanocytes due to cell death. Though Trpm7 is permeable to many different ions, we hypothesized that the melanocyte cell death phenotype is due to aberrant magnesium homeostasis from Trpm7 loss. To test this, we knocked out a magnesium exporter, slc41a1. We hypothesized that knocking out slc41a1 would raise intracellular magnesium levels and suppress the cell death phenotype in trpm7 mutants. While we did see suppression, we discovered that is was most likely due to the targeting of another slc41a family member. Because these family members are mostly only permeable to magnesium, we have strong evidence that the trpm7 mutant melanocyte phenotype is due to aberrant magnesium homeostasis.
Parkinson’s Disease is one disorder that has been linked to magnesium deficiency. To better understand whether magnesium could be protective against this disease, we removed the exporter Slc41a1 from zebrafish and a rat cell model and assayed how this affected the survivability of dopaminergic neurons. We found that knocking down slc41a1 alone did not confer any protection to these neurons.
Though not connected to magnesium homeostasis, we also used the zebrafish model system to test promising anti-convulsive medications. This is important for epileptic patients who do not respond to the currently available drugs. Using behavioral testing, we showed that an anti-addiction medication called naltrexone can reduce seizures in different models.
- Academic Unit
- Craniofacial Anomalies Research Center; Interdisciplinary Graduate Program in Molecular Medicine
- Record Identifier
- 9983949695302771
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