Fragmentation for selection: how the deleterious mt DNA is removed in the female germline

Mitochondria are the energy factories and metabolic centers of cells,and their malfunction can lead to multiple human diseases.As highly dynamic organelles,mitochondria undergo frequent fission and fusion processes[1].The fusion process enables the exchange of inner materials between individual mitochondrion.The materials from healthy mitochondria could potentially compensate for the defects found in the defective mitochondria.Fission processes not only increase the mitochondrial number but also separate the damaged parts of mitochondria from the healthy ones,thus,facilitating the elimination of the defective mitochondria through a process known as mitophagy.Excessive fusion leads to extra connections and branching of the mitochondria,whereas extra fission results in fragmentation of mitochondria.The fusion and fission processes are differently tuned in various tissues to adapt to different physiological requirements[2].