Mitochondrial fission factor Drp1 is essential for embryonic development and synapse formation in mice

Mice that lack the fission mitochondrial GTPase Drp1, are shown to die during embryonic development. Although Drp1 is not required for apoptosis, the absence of Drp1 leads to neuronal and synaptic defects due to a failure of elongated mitochondria to reach distal parts of axons. Mitochondrial morphology is dynamically controlled by a balance between fusion and fission. The physiological importance of mitochondrial fission in vertebrates is less clearly defined than that of mitochondrial fusion. Here we show that mice lacking the mitochondrial fission GTPase Drp1 have developmental abnormalities, particularly in the forebrain, and die after embryonic day 12.5. Neural cell-specific (NS) Drp1 −/− mice die shortly after birth as a result of brain hypoplasia with apoptosis. Primary culture of NS- Drp1 −/− mouse forebrain showed a decreased number of neurites and defective synapse formation, thought to be due to aggregated mitochondria that failed to distribute properly within the cell processes. These defects were reflected by abnormal forebrain development and highlight the importance of Drp1-dependent mitochondrial fission within highly polarized cells such as neurons. Moreover, Drp1 −/− murine embryonic fibroblasts and embryonic stem cells revealed that Drp1 is required for a normal rate of cytochrome c release and caspase activation during apoptosis, although mitochondrial outer membrane permeabilization, as examined by the release of Smac/Diablo and Tim8a, may occur independently of Drp1 activity.