The ability to produce specific neuronal populations will be key to the development of cell-based therapeutics for neurological diseases. By studying the complex molecular mechanisms that neural stem cells (NSCs) engage during the production of neurons, we aim to reverse-engineer key determinants of neurogenesis useful for the directed production of specific neuronal subtypes. We have recently shown that the chromatin remodeling factor Mixed lineage leukemia-1 (Mll1) is specifically required for adult mouse SVZ neurogenesis but not for gliogenesis or stem cell identity. Mll1-deficient cells do not express the pro-neural transcription factor Dlx2 and transfection of Dlx2 into Mll1-deficient cells rescues neurogenesis and produces Tuj1+ cells with neuronal phenotypes, thus identifying Dlx2 as a key mediator in neuronal differentiation among SVZ NSCs. Cortical white matter also contains a small population of glial precursor cells that, like Mll1- deficient cells, can produce glia but are not normally neurogenic. Under certain conditions, however, these non-neurogenic cells can be induced to differentiate into neurons. Such cortical astrocytes may therefore represent a potential source of neurogenic cells for cell replacement or neuroregeneration therapies that is more abundant and easier to obtain than the deeper SVZ NSCs. We have preliminary data that shows that Dlx2 overexpression can drive normally non-neurogenic cortical astrocytes down a neuronal pathway, again suggesting the potential of Dlx2 as a powerful tool for inducing neurogenesis. The goal of this research proposal is to further explore the role of Dlx2 in both the rescue of neurogenesis in Mll1-deficient cells and the induction of neurogenesis in normally non-neurogenic cortical astrocytes. We hypothesize that Dlx2 expression will induce specific subtypes of GABA-ergic neurons. Dlx2 will be expressed in Mll1-deficient SVZ NSCs and wildtype cortical astrocytes using a lentiviral vector system. We will then use immunocytochemistry to characterize the subtypes of neurons generated and electrophysiology to confirm neuronal function. Overall, this data will further our understanding of the role of Dlx2 in neurogenesis and provide clues about how to coax cells in normally non-neurogenic brain regions such as the cortical white matter into neuronal fates for cell replacement therapies.
Stem cell therapies hold promise for replacing dead or damaged neurons in conditions such as traumatic brain injury, epilepsy, or Parkinson's disease, but stem cells are often difficult to obtain. This study explores ways to make neurons from other types of brain cells that may be easier and safer to obtain than stem cells. Such methods could become powerful tools in the treatment of brain disorders.
| Potts, Matthew B; Siu, Jason J; Price, James D et al. (2014) Analysis of Mll1 deficiency identifies neurogenic transcriptional modules and Brn4 as a factor for direct astrocyte-to-neuron reprogramming. Neurosurgery 75:472-82; discussion 482 |
