Final Report Summary - HND (Mechanisms of Human Neuronal Development and Functional Integration in Neural Network)
Human cell reprogramming technologies offer access to live human neurons from patients and provide a new alternative for modeling neurological disorders in vitro. Neural electrical activity is the essence of nervous system function in vivo. Therefore, we examined neuronal activity in media widely used to culture neurons. We found that classic basal media, as well as serum, impair action potential generation and synaptic communication. To overcome this problem, we designed a new neuronal medium (BrainPhys basal + serum-free supplements) in which we adjusted the concentrations of inorganic salts, neuroactive amino acids and energetic substrates. We then tested that this new medium adequately supports neuronal activity and survival of human neurons in culture. Long-term exposure to this physiological medium also improved the proportion of neurons that were synaptically active. The medium was designed to culture human neurons but also proved adequate for rodent neurons. The improvement in BrainPhys basal medium to support neurophysiological activity is an important step toward reducing the gap between brain physiological conditions in vivo and neuronal models in vitro. (Bardy et al. PNAS 2015)
Cell reprogramming technologies are revolutionizing medical research. An important challenge faced by neurobiologists is cellular heterogeneity, and better ways to identify/sort relevant cell types are needed. Human neural progenitors develop into electrophysiologically mature neurons at variable rates, providing challenges to in vitro studies of neurological disorders. Based on functional properties, we defined five electrophysiological types of neurons, which followed a developmental continuum. Whole-cell electrophysiology remains the gold-standard for functional evaluation. However, the large-scale analyses needed for translational studies require additional high-throughput molecular methods. We examined neuronal cultures derived from induced-pluripotent-stem-cells by combining single-cell measurements of electrophysiological activity, morphology and the transcriptome. This analysis showed strong correlations between action potential physiology, synaptic activity, dendritic complexity and gene expression. These correlations pointed out the importance of isolating functionally comparable neuronal samples. Our single-cell RNA sequencing analysis revealed genes that are expressed specifically in electrophysiologically mature human neurons. We used this molecular signature to isolate functional neurons. Altogether, this study opens up a new avenue for efficient large-scale prediction and analysis of functional cell types based on molecular signatures. Breaking the barrier of efficiently discerning mature electrophysiological types of neurons will expand the relevance of neuronal models in vitro. (Bardy et al. in revision 2015)
Cell reprogramming technologies are revolutionizing medical research. An important challenge faced by neurobiologists is cellular heterogeneity, and better ways to identify/sort relevant cell types are needed. Human neural progenitors develop into electrophysiologically mature neurons at variable rates, providing challenges to in vitro studies of neurological disorders. Based on functional properties, we defined five electrophysiological types of neurons, which followed a developmental continuum. Whole-cell electrophysiology remains the gold-standard for functional evaluation. However, the large-scale analyses needed for translational studies require additional high-throughput molecular methods. We examined neuronal cultures derived from induced-pluripotent-stem-cells by combining single-cell measurements of electrophysiological activity, morphology and the transcriptome. This analysis showed strong correlations between action potential physiology, synaptic activity, dendritic complexity and gene expression. These correlations pointed out the importance of isolating functionally comparable neuronal samples. Our single-cell RNA sequencing analysis revealed genes that are expressed specifically in electrophysiologically mature human neurons. We used this molecular signature to isolate functional neurons. Altogether, this study opens up a new avenue for efficient large-scale prediction and analysis of functional cell types based on molecular signatures. Breaking the barrier of efficiently discerning mature electrophysiological types of neurons will expand the relevance of neuronal models in vitro. (Bardy et al. in revision 2015)