Revolutionary view of two ways to split a mitochondrion

Abstract

Organelles called mitochondria divide in at least two contexts: during cell growth and in response to mitochondrial damage. The finding that division is different in these two contexts sheds light on the regulatory pathways involved.

Keywords: Cell biology; Imaging.

Figure 1 |. Two pathways for mitochondrial division.

Kleele et al. report microscopy studies of organelle division in mammalian cells, which reveal that mitochondria can divide in two ways. a, Midzone division is associated with mitochondrial division during cell growth. The organelle divides in the middle, and this process is associated with the protein DRP1, filaments of actin protein, and contact with another organelle – the endoplasmic reticulum (ER). The dividing mitochondrion is healthy and has replicating mitochondrial DNA (mtDNA). b, Peripheral division is associated with damaged mitochondria. This division also requires DRP1, but the dividing mitochondrion makes contact with a different organelle, the lysosome. This asymmetric division occurs at the tip of the mitochondrion. The dividing organelle has different properties on either side of the division site in terms of the membrane potential and the level of reactive oxygen species (ROS) and calcium ions (Ca²⁺). The authors observed that the smaller mitochondrial portion often lacked replicating mtDNA (and in 32% of the divisions it lacked any mtDNA), and that this portion of the organelle was degraded.