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Analyzing Mitochondrial Transport and Morphology in Human Induced Pluripotent Stem Cell-Derived Neurons in Hereditary Spastic Paraplegia
Published on: February 9, 2020
Modeling mitochondrial dynamics during in vivo axonal elongation
Matthew O'Toole1, Robert Latham, Rehan M Baqri
1Department of Mathematics, Michigan State University, A-106 Wells Hall, East Lansing, MI 48824-1115, USA.
Journal of Theoretical Biology
|October 11, 2008
Summary
Axonal elongation in Drosophila larvae is driven by quadratically increasing mitochondrial production over time, maintaining constant density via a homeostatic mechanism, suggesting an "axonal length sensor".
Area of Science:
- Developmental Biology
- Neuroscience
- Cell Biology
Background:
- Traditional axonal elongation models assume soma-driven material production.
- In vivo axonal growth is influenced by animal body size and growth rate.
- Fundamental questions remain regarding in vivo axonal material production and density.
Purpose of the Study:
- To investigate material production dynamics during in vivo axonal elongation.
- To determine mitochondrial density profiles and half-life in growing axons.
- To develop a mathematical model explaining observed mitochondrial distribution.
Main Methods:
- Measurement of length, mitochondrial density, and mitochondrial half-life in Drosophila larval medial segmental nerves.
- Analysis of 1st, 2nd, and 3rd instar Drosophila larvae over a 96-hour period.
- Derivation of a mathematical model to explain mitochondrial distribution patterns.
Main Results:
- Larval nerves linearly increased in length at an average rate of 9.24 micrometers/hour.
- Mitochondrial density increased at an average rate of 4.49x10^-3 mitochondria/micrometer/hour.
- Mitochondria exhibited a half-life of 35.2 hours; mathematical modeling indicated quadratic production increase and homeostatic density maintenance.
Conclusions:
- In vivo axonal elongation involves complex relationships between length and mass production.
- Cellular production of mitochondria increases quadratically over time during larval development.
- A homeostatic mechanism likely maintains constant mitochondrial density along the axon, suggesting an 'axonal length sensor'.
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