John Laboratory
Beker Multiple Sclerosis Research Laboratory

The John Laboratory (Beker Multiple Sclerosis Research Laboratory is part of the Corinne Goldsmith Dickinson Center for Multiple Sclerosis, the Department of Neurology, and the Friedman Brain Institute. Our research focuses on identifying novel avenues to restrict tissue damage and promote repair in inflammatory and demyelinating CNS conditions, notably multiple sclerosis (MS), neuromyelitis optica (NMO), and viral encephalitis. MS is the most common non-traumatic cause of paralysis in young adults in the US and Europe, the symptoms of which are driven by autoimmune demyelination of CNS white matter, while NMO is a rare but aggressive autoimmune MS-like condition characterized by spinal cord and optic nerve lesions, paralysis, and blindness.

Our research aims to understand the mechanisms underlying lesion pathogenesis and repair in these conditions, and focuses on how the environment within the CNS controls inflammatory lesion size and the potential for repair. We make extensive use of conditional genetic models in which developmental myelin formation, and demyelination and remyelination in adults, are accelerated or impaired. Phenotypes in conditional knockout models developed in the lab are then interrogated using genome-scale analyses of transcription and chromatin occupancy, confocal imaging, and electron microscopy. The goal of this work is to identify novel therapies to prevent lesion formation and protect patient health, and to repair existing damage and promote return of function. Our research is funded by the National Institutes of Health, the National MS Society, the Guthy-Jackson Foundation, pharmaceutical and biotech industry collaborations, and private benefactors.

In vitro co-culture model of CNS myelination. his image illustrates a CNS co-culture of neurons (green) and myelinating oligodendrocytes (red), in which myelin segments appear as linear yellow profiles. This image appeared on the cover of the August 2011 issue of The Journal of Immunology, accompanying an article from our laboratory. In the article, we showed that the growth factor IL-11 promotes myelin repair in MS models via a balance in activity of Stat3 versus Stat1 signaling. Zhang, J., Y. Zhang, D. J. Dutta, A. T. Argaw, V. Bonnamain, J. Seto, D. A. Braun, A. Zameer, F. Hayot, C. B. Lòpez, C. S. Raine, and G. R. John. 2011. Proapoptotic and antiapoptotic actions of Stat1 versus Stat3 underlie neuroprotective and immunoregulatory functions of IL-11. J. Immunol. 187: 1129–1141. NIHMSID: NIHMS299922 PubMed [journal] PMID:21709156, PMCID: PMC3164308

Research

Project 1. How does the environment of the CNS control inflammatory lesion size and the potential for repair?

Astrocytes are the most numerous cell type in the mammalian CNS, and respond to inflammation or injury with a graded transcriptional program driven by pro- or anti-inflammatory mediators. These changes, called reactive astrogliosis, profoundly impact surrounding neural and non-neural cells. One of the major goals of our work is to understand the functional impact of reactive astrogliosis on other cell types within the CNS, with a translational focus.

Recently, we have found that an astrocyte-derived family of growth factors, which signal via the gp130 receptor and the transcription factor Stat3, are required for normal CNS white matter formation and myelination, and that these factors act in part via transcriptional activators of the Kruppel-like factor (Klf) family. Conditional inactivation of Stat3 or Klf6 in the precursors of myelinating cells, called oligodendrocyte progenitors, results in failure of CNS myelination and complete absence of white matter formation. We are currently investigating whether the Stat3-Klf6 axis is also required for successful repair of myelin and return of function in models of MS.

Conditional inactivation of Stat3-Klf6 signaling causes failure of CNS myelination. Pseudocolored electron micrograph of spinal cord white matter tracts from a 19 day old mouse pup in which the transcriptional activator Klf6 has been conditionally inactivated in the progenitors of myelinating cells (oligodendrocyte progenitor cells). The photograph shows unmyelinated axons (colored circles) surrounded by glial processes (shown in pale blue). At this stage of development, axons in spinal cord white matter should be fully myelinated, but our work shows that inactivation of Stat3-Klf6 signaling results in complete failure of CNS myelination and white matter formation. Magnification, x2000. This image is taken from our publication: Laitman BM, Asp L, Mariani JN, Kramer EG, Pedre X, Dutta DJ, Lee Y-M, Liu J, Zhang J, Argaw AT, Zaslavsky E, Braun DG, Pham T, Horng S, Hara Y, Lu QR, Narla G, Raine CS, Casaccia P, Friedman SL, John GR. The transcriptional activator Krüppel-like factor-6 is required for CNS myelination. PLoS Biology, In Press.

Project 2. What are the mechanisms controlling entry of inflammatory cells into the CNS parenchyma?

Inflammatory lesions in conditions such as MS and NMO are characterized by entry of inflammatory cells and soluble factors (such as antibodies) into the CNS parenchyma. These events are associated with breakdown of the blood-brain barrier (BBB), which in healthy adults separates the CNS from the rest of the body. The BBB is an endothelial barrier, but its integrity is controlled by other cell types, notably astrocytes and pericytes.

Importantly, our research has identified reactive astrocytes as key controllers of BBB permeability in inflammatory lesions, acting via plasticity factors such as VEGF-A and ECGF1/TP. Most notably, we have found that genetic or therapeutic blockade of these astrocyte-derived factors limits BBB disruption and inflammatory cell and antibody entry, and reduces neurologic deficit in models of MS. These studies have generated an FDA-approved phase Ib clinical trial testing the impact of VEGF-A blockade on disease exacerbation in NMO patients (ClinicalTrials.gov: NCT01777412). We are currently investigating the molecular mechanisms by which reactive astrocytes regulate BBB permeability, and whether they also directly regulate leukocyte migration in inflammatory CNS lesions.

Astrocytes are key regulators of endothelial permeability in the adult CNS. Three-dimensional confocal image of adult mouse cerebral cortex immunostained to show astrocytes (in green) and microvascular endothelial cells (in red). Note the intimate contact between the two cell types. Our research has helped to show that astrocytes are critical regulators of endothelial permeability in the mammalian CNS, and as such play a key role in controlling entry of inflammatory cells into the brain in conditions such as multiple sclerosis. Magnification, X200. This image is taken from our publication: Argaw AT, Asp L, Zhang J, Navrazhina K, Pham T, et al. Astrocyte-derived VEGF-A drives blood-brain barrier disruption in CNS inflammatory disease. Journal of Clinical Investigation. 2012; 122(7):2454-68. PubMed [journal] PMID: 22653056, PMCID: PMC3386814, and image on JCI Facebook page as the June 2012 Scientific Show Stopper.
Zhang, J., Y. Zhang, D. J. Dutta, A. T. Argaw, V. Bonnamain, J. Seto, D. A. Braun, A. Zameer, F. Hayot, C. B. Lòpez, C. S. Raine, and G. R. John. 2011. Proapoptotic and antiapoptotic actions of Stat1 versus Stat3 underlie neuroprotective and immunoregulatory functions of IL-11. J. Immunol. 187: 1129–1141. NIHMSID: NIHMS299922 PubMed [journal] PMID:21709156, PMCID: PMC3164308
John Gareth

Dr. Gareth John

The John Lab (Beker Multiple Sclerosis Research Laboratories) researches mechanisms controlling lesion formation and repair in inflammatory diseases of the central nervous system.