Friday, 10 April 2015

What is the function of mitochondrial networks? A theoretical assessment of hypotheses and proposal for future research

 Hanne Hoitzing, Iain G. Johnston and Nick S. Jones

Mitochondria are dynamic organelles: sometimes they are fragmented, sometimes they form giant fused networks across the cell, and sometimes they take on intermediate shapes. What is the reason for having these different possible morphologies?

In this paper we discuss the function of large fused mitochondrial networks. Some hypotheses existing in the literature are being discussed, and some new ones are proposed. A mathematical perspective is taken. Coarse-grained models, simulations and estimations are used to try to gain insights. To enable a mathematical description of mitochondrial fusion, the terms microfusion, mesofusion, static hyperfusion and dynamic hyperfusion are introduced. Improvements for models are suggested, and future experiments are proposed.

Among the insights found are the possibilities that selective fusion alone leads to an increase in mitochondrial quality control; that increased fusion may have non-linear effects on the diffusion rate of proteins; that the effect on membrane potential of fusion may be more complicated than a simple averaging; and that fusion can act to dampen biochemical fluctuations.

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