Grey Fox Lung Cells with mEmerald-α-Actinin and mCherry-Mito
In animal species, mitochondria are principally inherited through the maternal lineage, though recent experimental evidence proposes that mitochondria may also be inherited via a paternal route in rare instances. Normally, a sperm carries mitochondria in its tail as an energy source for its expedition to the egg. During fertilization, the tail detaches, resulting in the only mitochondria the new organism gets - from the egg its mother provided. Thus unlike nuclear DNA, mitochondrial DNA doesn't get mixed up, so it is assumed to transform at a slower rate, which makes it useful for the study of human evolution.
The digital video sequence featured in this section explores mitochondrial dynamics in relation to the actin cytoskeleton. Mitochondria were visualized with mCherry fused to a mitochondrial targeting sequence and microfilaments and other actin-rich structures were fluorescently tagged with mEmerald fused to alpha-actinin, an actin-binding protein. Individual mitochondria are roughly oblong in shape and range in length from about 1 to 10 micrometers. The energy-generating organelles are very active and motile within the cytoplasm, however, and seem to shift shape and move almost continuously. They are also often organized together into groups, traveling chains, or other formations.
The fluorescent protein employed to label mitochondria in this selection of videos, mCherry, is a red fluorescent protein from the mFruit series. The intrinsic brightness of mCherry is approximately half that of EGFP, but its photostability is significantly better than that of the brighter red mFruit fluorescent protein mStrawberry. Excitation and emission maxima of mCherry occur at 587 and 610 nanometers, respectively. mEmerald, employed here to tag alpha-actinin, is a bright, photostable EGFP variant. Excitation and emission peaks of mEmerald occur at 487 nanometers and 509 nanometers, respectively.