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Published on: July 13, 2011
Patient mutations in DRP1 perturb synaptic maturation of cortical neurons
T B Baum1, C Bodnya1, J Costanzo1
1Vanderbilt University, Cell and Developmental Biology, Nashville, TN.
Insights
Mutations in the DNM1L gene disrupt mitochondrial fission, leading to severe neurodevelopmental disorders. This study shows mutation-specific effects on neuronal development and synaptic function, impacting calcium regulation and neuronal activity.
Area of Science:
- Neuroscience
- Genetics
- Cell Biology
Background:
- De novo loss-of-function mutations in DNM1L, encoding dynamin-related protein 1 (DRP1), are linked to severe neurodevelopmental phenotypes.
- Mitochondrial fission, regulated by DRP1, is crucial for developing brain metabolism, but the specific impact of DRP1 mutations on cortical development remains unclear.
Purpose of the Study:
- To investigate how DRP1 mutations in different domains uniquely disrupt cortical development and synaptic maturation.
- To model early cortical development in vitro using patient-derived induced pluripotent stem cells (iPSCs).
Main Methods:
- Utilized iPSCs from patients with DRP1 mutations (GTPase or stalk domains) to create cortical neurons in vitro.
- Employed high-resolution time-lapse imaging to analyze axonal transport and mitochondrial motility.
- Conducted transcriptional profiling and live functional calcium imaging of mutant neurons.
- Applied super-resolution microscopy to assess pre- and post-synaptic marker colocalization.
Main Results:
- Observed mutation-specific alterations in mitochondrial motility, with severely hyperfused mitochondria in mutant neurons.
- Transcriptional profiling revealed mutation-dependent changes in genes related to synaptic development and calcium regulation.
- Confirmed disruptions in calcium dynamics and deficits in synaptic marker colocalization in DRP1 mutant neurons.
Conclusions:
- Altered mitochondrial morphology in DRP1 mutant neurons contributes to pathogenic dysregulation of synaptic development and activity.
- These findings highlight mutation-specific impacts of DRP1 dysfunction on neuronal development and function.
- Provides a cellular model for studying DRP1-related neurodevelopmental disorders.
Abstract:
With the advent of exome sequencing, a growing number of children are being identified with de novo loss of function mutations in the dynamin 1 like (DNM1L) gene encoding 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 induced pluripotent stem cells (iPSCs) harboring DRP1 mutations in either the GTPase or stalk domains to model early stages of cortical development in vitro. High-resolution time-lapse imaging of axonal transport in mutant DRP1 cortical neurons reveals mutation-specific changes in mitochondrial motility of severely hyperfused mitochondrial structures. Transcriptional profiling of mutant DRP1 cortical neurons during maturation also implicates mutation dependent alterations in synaptic development and calcium regulation gene expression. Disruptions in calcium dynamics were confirmed using live functional recordings of 100 DIV (days in vitro) mutant DRP1 cortical neurons. These findings and deficits in pre- and post-synaptic marker colocalization using super resolution microscopy, strongly suggest that altered mitochondrial morphology of DRP1 mutant neurons leads to pathogenic dysregulation of synaptic development and activity.
