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XI European Meeting on Glial Cell Function in Health and Disease

Overview Session Overview Sessionprint print  
 

July 3, 2013 - Room 1 11:10am - 12:55pm
Workshop II (continued): In Vivo Analysis of Glial Cells: Promises and Pitfalls of Genetic Manipulation

Organized by
Dwight E. Bergles (Johns Hopkins University, Baltimore, USA)

11:10am
W02-04

Neuron-glia interactions: models matter

*Frank W.  Pfrieger 1
1 University of Strasbourg, Institute of Cellular and Integrative Neurosciences, CNRS UPR 3212, Strasbourg, France
Abstract text :

Brain development and function depend on interactions of neurons and different type of glial cells. A profound understanding of these interactions requires experimental approaches that allow for targeted manipulations of specific glial cells in vivo. In my presentation, I will present transgenic mouse models that we developed to study the relevance of glial substance release in the retina.



11:45am
W02-05

In vivo analysis of genetic contribution to glial development and functions at cellular resolution using MADM mouse model

*Hui Zong 1 , Chong Liu 1 , P. Brit Ventura 1 , Phil Gonzalez 1
1 University of Virginia, , Charlottesville, United States
Abstract text :

Nervous system is an intricately wired network of neuronal and glial cells. While many fundamental functions of the nervous system are executed through neuronal circuitry, the importance of glial cells in the development, nourishing, and activity-modulation of the nervous system have been increasingly appreciated. Since glial cells intimately associate with neurons, blood vessels, and other cell types, it is important to use model organisms to study their in vivo functions. While knockout mouse models have been widely used to study genetic regulation of glial development and functions, the embryonic lethality and other pleiotropic problems caused by gene knockout in a large population of cells often confound the data interpretation. Furthermore, cellular resolution necessary for studies of cell-autonomous functions as well as cell-cell interactions has been hard to achieve due to the lack of reliable labeling method.


To circumvent these problems, we established a mouse genetic mosaic system termed MADM (Mosaic Analysis with Double Markers) [Zong 2005 Cell]. Through Cre-loxP mediated inter-chromosomal mitotic recombination between two homologous chromosomes, the MADM system can generate homozygous mutant cells that are unequivocally labeled by green fluorescent protein (GFP) and their sibling WT cells labeled by red fluorescent protein (RFP) within an otherwise colorless, normal mouse. Due to the low probability of the recombination between chromosomes, mutant cells generated by MADM are very sparse (0.1-1% or much lower), allowing the analysis of cell-autonomous functions of mutant cells. Sparsely labeled cells also enable high-resolution analysis of the interactions between GFP-labeled mutant cells and neighboring normal cells. Importantly, with the permanent GFP-labeling, progeny of mutant cells can be studied along each and every lineage for their developmental potentials. Last but not least, the RFP-labeled WT sibling cells within the same animal provide an excellent internal control for in vivo phenotypic analysis of mutant cells. Here I will present our recent studies with MADM-based brain tumor models that revealed the involvement of a specific glial cell lineage in glioma [Liu 2011 Cell] and a cellular reprogramming phenomenon in medulloblastoma. In combination with other glia-specific genetics tools, MADM should be highly valuable to study genetic contribution to many aspects of glial development and functions.



12:20pm
W02-06

Challenges of manipulating gene expression in dynamic glial cells

*Dwight Bergles 1
1 Johns Hopkins University, , Baltimore, United States
Abstract text :

The mammalian CNS contains an abundant, widely distributed population of glial cells that expresses the chondroitin sulfate proteoglycan NG2 (CSPG4) and the alpha receptor for PDGF (PDGFaR).  Although initially defined as a class of astrocytes, studies completed over the past two decades indicate that these cells are distinct from astrocytes, in that they do not express GFAP, do not contact capillaries and do not express glutamate transporters at high densities. These NG2 cells serve as progenitors for oligodendrocytes (OLs) during early development, and are often referred to as oligodendrocyte precursor cells (OPCs).  However, NG2 cells remain abundant in the mature CNS after myelinated tracts have been established, accounting for 5-10% of all cells, and they retain the ability to proliferate throughout life.  These cells undergo dramatic morphological changes and increase their proliferation following acute CNS injury and in neurodegenerative diseases; nevertheless, the contribution of these cells to regeneration and tissue repair remains uncertain.  Over the past several years we have developed new lines of transgenic mice that have allowed us to manipulate gene expression within these progenitors, track their fate, monitor their dynamics on timescales of minutes to months in vivo, and selectively ablate these cells from the adult CNS. These studies are providing new insight into the ability of these cells to maintain their density in the adult CNS, regenerate oligodendrocytes in the context of disease, and participate in tissue repair following acute CNS injury. In this presentation, I will discuss our experience with various transgenic mouse lines that enable manipulation of these cells in vivo, and the general difficulties associated with studies of highly dynamic cell populations.