Effect of DRP1 mutations on synaptic development during iPSC-derived cortical neuron maturation

With the advent of exome sequencing, a growing number of children are being identified with de novo loss of function mutations in the large GTPase essential for mitochondrial fission - Dynamin Related Protein 1 (DRP1); these mutations result in severe neurodevelopmental phenotypes such as developmental delay, optic atrophy, and epileptic encephalopathies. Though it is established that mitochondrial fission is an essential precursor to the rapidly changing metabolic needs of the developing cortex, it is not understood how identified mutations in different domains of DRP1 uniquely disrupt cortical development and synaptic maturation. We leveraged the power of both high-resolution imaging and induced pluripotent stem cells (iPSCs) harboring DRP1 mutations in either the GTPase or stalk domains to model early stages of cortical development. Transcriptional profiling of mutant DRP1 cortical neurons during maturation, as well as imaging of organelle dynamics and neuronal synapses, strongly suggests that altered mitochondrial morphology of DRP1 mutant neurons affect synaptic development leading to pathogenic dysregulation of synaptic activity.