Mouse OPCs were isolated from wild type neonatal cortices (at birth) by expansion within mixed glial culture for 8 days, purified, and subsequently differentiated as an OP-enriched culture. Cells were co-immunolabeled with VGF (red) and Chromogranin-B (green)at 4 days after purification. Scale bar, 10μm.
Triple-immunolabeling with the Purkinje cell marker Zebrin II (magenta), Pan-H3Ac (red) and VGlut2 (green) in the posterior zone of the developing cerebellum at P15.
Transmission electron microscopy (TEM) image of a mature Purkinje neuron at P21.
Golgi-Cox staining using silver nitrate reveals the complexity in the dendritic branching of a wild type Purkinje neuron at P20.
Coronal sections through the posterior zone of the adult mouse cerebellum reveals robust expression of the homeobox transcription factor Engrailed-1/2 (green) and the epigenetic factor MeCP2 (red) in all cell lineages. Merged image is shown on rightmost panel.
TEM of adult Purkinje neurons upon ablation of the chromatin remodeling protein ATRX during the postnatal stage.
Laboratory of Neuro-Repair
The Laboratory of Neuro-Repair works on the natural mechanisms that trigger brain repair. We are currently focused on the role of the growth factor/neuropeptide VGF (non-acronymic) and the regulation of gene expression through environmental enrichment such as exercise. Our studies employ a diverse array of biological and biochemical techniques including mouse transgenesis, primary tissue culture, virology, proteomics, high resolution microscopy and high-throughput sequencing. We also investigate the post-transcriptional role of A-to-I RNA editing (Adenosine to Inosine) in mechanisms associated to neuronal synaptic plasticity.
Laboratorio de Neuro-Reparación
El Laboratorio de Neuro-Reparación investiga los mecanismos de reparación del cerebro a través del factor de crecimiento/neuropéptido VGF (no acrónimo) y la regulación de la expresión génica a través del ejercicio. Este emplea una diversidad de técnicas de la biología molecular, transgénesis en modelos murinos, cultivo celular, virología, proteómica, secuenciación de alto rendimiento y microscopía de alta resolución. En una línea de investigación paralela, estudiamos el rol del “A-to-I RNA-editing” (Adenosina a Inosina edición del RNA) en mecanismos asociados a la plasticidad sináptica neuronal.
Cellular and molecular mechanisms that regulate OPC proliferation in pathological conditions
The capacity of the brain to regenerate has been debated for decades amongst neurobiologists. In fact, the history of adult mammalian neurogenesis is quite controversial. Primary evidence arose from the work in rats of Josef Altman and Gopal Das in the 1960s. However, their pioneering work was not sufficient to change the existing paradigm that neurons did not have the capacity to regenerate in the adult brain. In the 70s, Fernando Nottebohm in birds and Michael Kaplan in rodents showed the existence of neurogenesis in the adult brain. In the 80s, neurogenesis in birds was widely accepted, but it was much harder for scientists to accept the view that adult neurogenesis also occurred in mammals. This notion was strongly refused by a major leader in developmental neurobiology, Dr. Pasko Rukic. His articles in the 70s and 80s strongly opposed adult neurogenesis in primates, suggesting that adult neurogenesis did not occur in higher mammals and was confined to lower mammalian species.
Work in the 90s by Elizabeth Gould, Peter Erikkson and Fred “Rusty’ Gage sparked a new era in the existence of adult mammalian neurogenesis. Nevertheless, a new paradigm has recently emerged: that the major cell types undergoing cell proliferation in the adult brain are not neurons, but myelin-producing cells: oligodendrocyte precursor cells (OPCs). These cells undergo adult oligodendrogenesis and are found in white and gray matter. The Neuro-Repair Laboratory is interested in understanding the basic biological principles that dictate how OPCs respond to the environment and how these cells interact with other cell types of the central nervous system to modulate natural brain repair mechanisms. Simply, we aim to understand the mechanisms of OPC proliferation, induction of oligodendrogenesis by neuronal activity, and de novo myelination of damaged neuronal circuits through a combinatorial approach utilizing the latest technologies available.
A-to-I RNA Editing & Chromatin Architecture
A second major focus of the laboratory is to understand the functional role of Adenosine-to- Inosine RNA Editing in mammalian neurons. Adenosine to Inosine (A-to-I) editing of RNA molecules is the main form of RNA editing in mammals. Adenosine deaminases acting on RNA (ADAR) enzymes are the catalytic components that carry out the hydrolytic demamination of Adenosine to Inosine. This chemical change is then recognized as Guanosine (G) by the translation machinery. Thus, A-to-I editing has the potential to diversify the proteome, create new splice sites and many other molecular alternatives that are yet to be discovered. It is now recognized that alterations in A-to-I RNA editing components underlie a wide array of neurodegenerative pathologies and cancers.
Our laboratory is focused on dissecting the role of chromatin architecture as a key structural component for the proper stability of subnuclear bodies (e.g. paraspeckles); processing and transport of RNA molecules (e.g. subcellular axonal transport); nuclear retention of multiple RNA species; and RNA secondary structure regulation.
We demonstrate how the chromatin remodeler protein Snf2l, also known as Smarca1 (OMIM #300012), regulates neuronal differentiation, and thus brain size. With novel approaches in high-throughput exome sequencing, it is now recognized that mutations in Snf2l may also underlie some forms of Rett Syndrome-like phenotypes (OMIM #312750),
We demonstrate how the chromatin remodeler protein Snf2h, also known as Smarca5 (OMIM #603375), regulates neuronal progenitor expansion in the embryonic and postnatal brain. We further show that Snf2h governs the morphogenesis of the adult mouse cerebellum, a major structure responsible for sensorimotor control and higher order cognitive processes. We highlight how Snf2h is mechanistically involved in histone H1 dynamics and chromatin plasticity.
We demonstrate that voluntary running activity can significantly extend the lifespan and ameliorate the ataxia-like phenotypes and short lifespan of the Snf2h cKO mouse model. We further decipher for the first time that the neuropeptide VGF (non-acronymic; not to be confused with VEGF; OMIM #602186) is strongly expressed in OPCs and plays a role within a mechanism of brain repair mediated by OPC expansion and subsequent myelination of damaged cerebellar circuits. We believe this work establishes a paradigm for exercise-induced brain repair in a neurodegenerative state and furthermore identifies a possible drug target (i.e. VGF) to stimulate endogenous remyelination. VGF encodes a secretory peptide precursor involved in synaptic plasticity and metabolism. VGF has been shown to be modulated by in vivo neuronal activity paradigms, such as exercise in the hippocampus, leading to the induction of other neurotrophic factors and synaptic remodeling. Additionally, VGF peaks in expression during axonal outgrowth and synaptogenesis in the maturing brain. Mouse VGF knockouts are small and hypermetabolic, suggesting a prominent role in energy metabolism. These results show that VGF plays diverse roles as a neurotrophic factor, neuroendocrine modulator, and mediator of a myelin-based brain repair mechanism.
Voluntary Running Triggers VGF-Mediated Oligodendrogenesis to Prolong the Lifespan of Snf2h-Null Ataxic Mice 0896/news
Key brain repair molecule identified https://mssociety.ca/research-news/article/ottawa-study-highlights-neuroprotective-effect-of-running-in-mouse-model-of-neurodegeneration-identifies-key-mediating-protein
Exercise is good for the brain http://www.pewtrusts.org/en/research-and-analysis/analysis/2016/10/17/exercise-is-good-for-the-brain-and-now-we-know-more-about-why