New Individual Predoctoral Fellowship Awards in 2007

Ayana Jordan, NIH Individual Predoctoral Fellowship Award for a project entitled "Mechanisms underlying T helper suppression by regulatory T cells." (Sponsor, Fernando Macian)

Lorena Hernandez, NIH Individual Predoctoral Fellowship Award for a project entitled "Characterization of the Invasion and Intravasation of Breast Cancer Cells." (Sponsor, Jeff Segall)

Toni Roberts, NIH Individual Predoctoral Fellowship Award for a project entitled "Mechanisms of Transmigration of HIV Infected Cells Across the Blood Brain Barrier." (Sponsor, Joan Berman)

Rachel Ross, NIH Individual Predoctoral Fellowship Award for a project entitled "Hypothalamic Fatty Acid Sensing in Aging." (Sponsor, Gary Schwartz & Luciano Rossetti)

Other Students Holding Individual Predoctoral Fellowships

See Below for Abstracts of Recent Projects

Ayana Jordan - ABSTRACT: The overall goal of this project is to elucidate the changes that occur within T helper (Th) cells when suppressed by regulatory T cells (Tregs) and identify the molecular mechanisms underlying Treg mediated inactivation of effector T cell functions. The specific aims of this project include (1) characterizing the role of Nuclear Factor of Activated T cells (NFAT) within suppressed T cells, identifying the molecular mechanisms of activation, transcriptional partners and the interaction with downstream targets; and (2) determining if Treg function is controlled by silencing of the interleukin (IL-) 2 gene. To approach the first aim, immunofluorescence will reveal if NFAT is retained in the cytoplasm or translocated across the membrane, where it is active and can induce the expression of proteins known to suppress T cell activation. Electrophoretic mobility shift assays will be used to determine if active NFAT proteins can bind DNA in the nucleus of suppressed Th cells, in the absence of AP-1. Subsequently, chromatin immunoprecipitation (ChIP) will be performed on suppressed Th1 cells to determine if activation by NFAT involves direct recruitment of this protein to the promoter regions of T cell inactivating genes. By completing our goals in aim one we intend to uncover the transcriptional regulation of NFAT activation within suppressed T cells and elucidate gene expression patterns that are necessary for the induction and maintenance of the unresponsive state. For the second aim, chromatin immunoprecipitation assays will determine if epigenetic modifications regulate IL-2 expression in stimulated Tregs and suppressed Th cells. To study the role of histone deacetylation in the suppressor activity and function of Tregs, isolated Tregs from BALB/c mice will be cocultured with TCR transgenic D011.10 mice and stimulated in the presence or absence of the histone deacetylase inhibitor, Trichostatin-A. Our overall goal in aim two is to determine the role that chromatin remodeling plays in the induction of T cell tolerance and investigate the mechanisms that regulate cytokine expression in Tregs and in Treg-mediated suppression of Th cells. A clear understanding of how the IL-2 locus is regulated in both Tregs and suppressed cells will prove invaluable in elucidating Treg behavior and function. By uncovering the mechanisms of Treg-mediated suppression of effector T cell function, novel therapies inducing immune tolerance can be developed against a host of autoimmune diseases and cancers. This project is relevant to the public at large because of the importance this cell (Treg) plays in maintaining a healthy immune system. By studying the behavior of this cell type (Treg), the causes of different human diseases can be better understood and new therapies developed.

Lorena Hernandez - ABSTRACT: Metastasis is a complex process that consists of a series of steps including invasion, intravasation, extravasation and growth to form micrometastasis in other tissues. Thus far, not much is known about what triggers cancer cells to invade and intravasate. Knowing more about these early steps of metastasis would help identify therapeutic targets to aid in the prevention of metastasis. To increase our current knowledge on the processes of invasion and intravasation the following specific aims are proposed: Aim I. Investigation of the in vivo invasive behavior of MTLn3-ErbB3 cells. ErbB3 overexpression has been shown to increase the metastatic behavior of MTLn3 cells in vivo as well as their chemotactic response to HRGa1 in vitro; therefore this cell line provides an opportunity to evaluate, using the in vivo invasion assay, whether there are other signaling pathways that regulate in vivo invasion aside from the published EGF/CSF-1 paracrine loop, as well as to assess the importance of macrophages for cancer cell invasion. Aim II. Determination of the "intravasation signature." Because not all cancer cells intravasate, those cancer cells that undergo the process must undergo gene expression changes indicative of the process. To begin to elucidate the gene changes occurring in breast cancer cells that intravasate, the global gene expression of intravasated MTLn3 cells will be compared to that of cancer cells remaining in the primary tumor using microarray analysis. The resulting "intravasation signature" will be compared to the existing invasion signature to assess the similarities/differences between these processes. Aim III. Characterization of the function of key genes in intravasation. To test the biological validity of the "intravasation signature", key genes from the "intravasation signature" will be selected to test their role in metastasis. Because motility has been previously characterized as an important feature of metastatic cancer cells, the effect of the selected genes in MTLn3 cells' ability to extend lamellipodia and chemotax will be evaluated. To test the genes' effect in MTLn3 metastatic behavior in vivo, blood burden and lung metastases will be determined. Metastasis is the number one cause of mortality in cancer patients. This project will increase our understanding of what triggers cancer cells to start the complicated process of metastasis, and will result in the generation of novel targets for therapies to aid in the prevention of metastasis.

Toni Roberts - ABSTRACT: With the success of HAART, HIV infected individuals are living longer and HIV mediated damage to the CNS, including HIV Associated Dementia (HAD) and other forms of neurocognitive impairment, are increasingly presenting as a devastating consequence of HIV infection. Although a late clinical finding, compromise of the blood brain barrier (BBB) and infiltration into the CNS parenchyma by HIV infected monocytes have been shown to occur early in infection. In fact, cognitive impairment correlates more directly with neuroinflammation than with the presence of virus within the CNS. CCL2, the predominate monocyte chemoattractant, has been shown to be substantially elevated in patients with HAD and HIV Encephalitis. Thus, understanding the mechanisms of HIV and CCL2 mediated monocyte transmigration into the CNS and concomitant disruption of the BBB will enable the identification of potential targets of therapy, with the ultimate goal of preventing HIV related neurocognitive decline. We hypothesize that HIV infection of monocytes alters their expression of CCR2, cell adhesion molecules, and adherens and tight junction proteins, and that transmigration of these infected monocytes in response to CCL2 in the CNS results in aberrant monocyte-BBB endothelial cell interactions, promoting enhanced migration and BBB disruption. The goal of this research is to define the molecular interactions responsible for the enhanced diapedesis by HIV infected monocytes into the CNS in response to the CCL2 chemokine and the subsequent BBB breakdown. The specific goals of this research are: (1) to identify differentially expressed genes or changes to protein localization in monocytes as a result of HIV infection and CCL2 chemotactic stimulation that may cofitribute to their enhanced diapedesis using microarray, RT-PCR, Western blot, and confocal imaging; (2) to characterize the effects of CCL2 on brain microvascular endothelial cell junction proteins that may potentiate monocyte diapedesis and disrupt BBB integrity using microarray, RT-PCR, Western blot, confocal imaging, and coimmunoprecipitation (ColP) studies; (3) to characterize the dynamic interactions between junctional proteins, adaptor proteins, and the cytoskeleton in HIV infected monocytes and in human brain microvascular endothelial cells that contribute to the enhanced transmigration properties of monocytes and disruption of BBB integrity in response to CCL2 using radiolabeling, ColP, Western blot, autoradiography, confocal imaging, and tissue staining; and (4) to determine the phosphorylation changes in cell juction proteins during transmigration of HIV infected monocytes across the BBB in response to CCL2 using radiolabeling, immunoprecipitation, autoradiography, and kinase and phosphatase inhibitors.

Rachel Ross - ABSTRACT: The goal of this thesis project is to determine whether the metabolism of fatty acid within the hypothalamus plays an important role in the regulation of energy and glucose homeostasis in aging. Specifically, I plan to induce bi-directional changes in the hypothalamic expression of two critical enzymes in fatty acid metabolism: malonyl-CoA decarboxylase (MOD) and carnitine palmitoyl transferase 1 (CPT1) and then examine their impact on the metabolic syndrome of aging in rats. I will pursue two experimental aims. 1) Identify the role of malonyl-CoA in the development of the metabolic syndrome of aging. I postulate that decreased cellular levels of malonyl-CoA lead to the progressive loss of lipid (and other nutrient) sensing in the hypothalamus of aging rats 2) Identify the role of LCFA-CoA in the development of the metabolic syndrome of aging. I postulate that decreased cellular levels of LCFA-CoA lead to the progressive loss of lipid (and other nutrient) sensing in the hypothalamus of aging rats. In doing these experiments, I will learn multiple physiologic, pharmacologic, and molecular techniques that will help me grow into an independent scientist while solving an important medical problem.