Timothy Vartanian, MD/PhD
Associate Professor of Neurology
Harvard Medical School/Beth Israel
Deaconess Medical Center

MRRC Project(s)

P01 NS38475-01
Periventricular Leukomalacia in the Premature Infant- PI, Prj 5: Cytokine-Mediated Oligodendrocyte Injury + Supplement for Individuals with Disabilities

R01 NS42317
Molecular Control of Oligodendrocyte Development

The overall hypothesis is that neuregulin mediated signals are necessary both at early, prior to terminal differentiation, and late stages of oligodendrocyte development including myelination. Specific Aim 1 focuses on the function of neuregulin mediated signals in early oligodendrocyte development. Specific Aim 2 will determine if neuregulin signals survival versus differentiation in early oligodendrocyte development. Specific Aim 3 will determine if the effects of erbB2, erbB3 or erbB4 on oligodendrocyte development are cell autonomous. Specific Aim 4 will determine if neuregulin is an axonal signal for terminal differentiation of oligodendrocytes and myelination.

Research Description

Highlights of Major Accomplishments

• Discovery that the neuronally-derived factor, neuregulin, acting through an erbB receptor tyrosine kinase mechanism, is critical for oligodendroglial development,

• Demonstration that the transcription factor CREB is involved in the neuregulin-mediated oligodendrocyte development,

• Demonstration that immature oligodendrocytes are highly vulnerable to cytokine-mediated death and identification of interferon-gamma as a key cytokine in this process.

Major Results

1. Oligodendroglial development

2. Cytokine-mediated oligodendroglial death

1. Oligodendroglial development

We have shown that Neuregulin-1 is one of the neuronally derived factors necessary for oligodendrocyte development to proceed. Cells within the oligodendrocyte lineage respond to neuregulins by activating members of the erbB receptor tyrosine kinase family (erbB2,3,4) which function as signal transducing heterodimers. Individual erbB receptor subunits within a functional heterodimer can deliver distinct molecular signals and we have found, through generation of an erbB2 null mouse, that the erbB2 receptor tyrosine kinase is necessary for oligodendrocyte development to proceed from an immature to a mature stage. In the presence of erbB2 (erbB2 +/+, erbB2+/-), spinal cord oligodendrocytes develop according to a predictable schedule with mature oligodendrocytes appearing by the equivalent of E17. However, in the absence of erbB2 (erbB2 -/-) oligodendrocyte development is halted at an immature stage, termed the preoligodendrocyte. In contrast, formation of neurites and astrocytes appears normal in erbB2 -/- spinal cord explants.

To test whether erbB2 defines a specific signal transduction pathway that may be necessary for progression from immature to mature oligodendrocytes we studied phosphorylation of the transcriptional regulator CREB, a well described downstream signaling event previously shown to be activated by erbB2/4 and erbB2/3 heterodimers. Spinal cord explants were treated with vehicle alone or neuregulin for 30 minutes, fixed, and studied for CREB phosphorylation using a polyclonal antibody specific for phospho-CREB (P-CREB). Wild type and erbB2+/-explants showed intense nuclear P-CREB immunoreactivity in response to neuregulin. P-CREB was identified both in cells within the oligodendrocyte lineage (O4+) as well as in other cells derived from the explant. In contrast, explants from embryos homozygous for the erbB2 null mutation showed little P-CREB immunoreactivity beyond background in response to neuregulin. Thus, erbB2 is necessary for neuregulin-induced CREB phosphorylation in spinal cord explants with developing oligodendrocytes.

2. Cytokine-mediated oligodendroglial death

To address the issue of cytokine-mediated oligodendroglial death we have studied both purified cultures and mixed cultures with carefully characterized cellular composition. Our data thus far have shown that (1) interferon-gamma is highly toxic to immature oligodendrocytes, (2) TNF-alpha is not toxic to immature oligodendrocytes alone but strikingly potentiates interferon-gamma mediated death, (3) interferon-gamma mediated oligodendrocyte death is apoptotic, (4) lipopolysaccharide induces death of developing oligodendrocytes in mixed glial cultures but not in purified cultures, (5) lipopolysaccharide-treated microglia secrete compound(s) toxic to immature oligodendrocytes, and (6) both interferon-gamma and lipopolysaccharide induce nitric oxide synthase in microglia. Thus, the data show a particular vulnerability of immature oligodendrocytes to specific cytokines and the likely cellular and molecular intermediaries involved in lipopolysaccharide-mediated oligodendrocyte death.

Publications

Vartanian T. Interferons and central nervous system glia. In: Reder AT. ed. Interferon Therapy of Multiple Sclerosis. NY: Marcel Dekker: 1997; 95-113.

Vartanian T, Goodearl A, Viehover A, Fischach G. Axonal neuregulin signals cells of the oligodendrocyte lineage through HER4 and Schwann cells through HER2 and HER3. J Cell Biol 1997; 137:211-220.

Vartanian T, DeLamonte S. Case records of the Massachusetts General Hospital. N Engl J Med 1999; 340:127-135.

Vartanian T, Fischbach GD, Miller RH. Failure of spinal cord oligodendrocyte development in the absence of neuregulin. Proc Natl Acad Sci USA 1999; 96:731-735.

GrandPre T, Nakamura F, Vartanian T, Strittmatter SM. Identification of the myelin-derived inhibitor of axon regeneration as a reticulon-related protein. Nature 2000; 403:439-444.

Vartanian T, Goodearl A, Lefebvre S, Park SK, Fischbach G. Neuregulin induces the rapid association of focal adhesion kinase with the erbB2-erbB3 receptor complex in schwann cells. Biochem Biophys Res Commun 2000;271(2):414-7.

Alberta J, Park-S-K., Mora J, Yuk D, Pawlitzky I, Iannarelli P, Vartanian T, Stiles CD, Rowitch DH. Sonic hedgehog signaling is required during an early phase of oligodendrocyte development in the mammalian brain. MCN 2001;18:434-444.

Goodearl A, Viehover A, Vartanian T. Neuregulin-induced association of Sos Ras exchange protein with HER2(erbB2)/HER3(erbB3) receptor complexes in Schwann cells through a specific Grb2-HER2(erbB2) interaction. Dev Neurosci 2001;23(1):25-30.

Viehover A, Miller RH, Park SK, Fischbach G, Vartanian T. Neuregulin: an oligodendrocyte growth factor absent in active multiple sclerosis lesions. Dev Neurosci 2001;23(4-5):377-86.

Park SK, Solomon D, Vartanian T. Growth factor control of CNS myelination. Dev Neurosci 2001;23:327-337.

Park SK, Miller R, Krane I, Vartanian T. The erbB2 gene is required for the development of terminally differentiated spinal cord oligodendrocytes. J Cell Biol 2001;154:1245-1258.

Hognason T, Chatterjee S, Vartanian T, Ratan RR, Ernewein KM, Habib AA. Epidermal growth factor receptor induced apoptosis: potentiation by inhibition of Ras signaling. FEBS Lett 2001;491:9-15.

Habib AA, Chatterjee S, Park SK, Ratan RR, Lefebvre S, Vartanian T. The epidermal growth factor receptor engages receptor interacting protein and nuclear factor-kappa B (NF-kappa B)-inducing kinase to activate NF-kappa B. Identification of a novel receptor-tyrosine kinase signalosome. J Biol Chem 2001;276:8865-8874.

Lehnardt S, Lachance C, Patrizi S, Lefebvre S, Follett PL, Jensen FE, Rosenberg PA, Volpe JJ, Vartanian T. The toll-like receptor TLR4 is necessary for lipopolysaccharide-induced oligodendrocyte injury in the CNS. J Neurosci 2002;22:2478-2486.

Wang X, Chun SJ, Treloar H, Vartanian T, Greer CA, Strittmatter SM. Localization of Nogo-A and Nogo-66 receptor proteins at sites of axon-myelin and synaptic contact. J Neurosci 2002;22:550-5-5515.

Vartanian T. An examination of the results of the EVIDENCE, INCOMIN, and phase III studies of interferon beta products in the treatment of multiple sclerosis. Clin Ther 2003;25(1):105-18.

Habib AA, Chun SJ, Neel BG, Vartanian T. Increased expression of epidermal growth factor receptor induces sequestration of extracellular signal-related kinases and selective attenuation of specific epidermal growth factor-mediated signal transduction pathways. Mol Cancer Res 2003;1:219-233.

Lehnardt S, Massillon L, Follet P, Jensen FE, Ratan RR, Rosenberg PA, Volpe JJ, Vartanian T. Activation of innate immunity in the CNS triggers neurodegeneration through a Toll-like receptor 4-dependent pathway. PNAS 2003;85:8514-8519.

Chun SJ, Rasband M, Sidman R, Habib AA, Vartanian T. Integrin-linked kinase is required for Laminin-2-induced oligodendrocyte cell spreading and CNS myelination. J Cell Biol 2004, in press.

See Dr. Vartanian's publications via PubMed

Contact Information

E-mail: Timothy Vartanian, MD/PhD
Associate Professor of Neurology
Harvard Medical School/Beth Israel
Deaconess Medical Center