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The Minority Access to Research Careers

2009-2010

Ms. Erika Escobar
Ms. Jessica Jimenez
Ms. Jacqueline Kimmey
Mr. Rey Martin
Mr. Guillermo Milian
Mr. Matt Pimentel
Mr. Ryan Quiroz

        
        


          
       
 
       
        

Ms. Erika Escobar
Mentor: Dr. April Pyle
Title: Factors that Control Pluoripotency and differentiation of Human Embryonic Stem Cells

Erika Escobar is a third year Physiological Science major and a first-year MARC student. She has been working with Dr. April Pyle in the MIMG department since Fall 2009. Under the supervision of Dr.
Jacquelyn Alva, Erika studies the role of AKT in the pluoripotency of human embryonic stem cells.

Human embryonic stem cells (hESC) have enormous potential for contributions to regenerative medicine. hESCs are derived from the inner cell mass of human blastocysts, in which the cells are pluripotent, meaning that they have the ability to differentiate into cells from all three embryonic germ layers. In addition to being pluripotent, hESC can undergo self-renewal, a process by which stem cells continuously divide to generate more stem cells. Before hESCs are able to safely contribute to regenerative medicine, the pathways that regulate their self-renewal and differentiation must be elucidated. A number of cellular pathways have been shown to play a role in hESC fate decisions, including the TGFß, BMP and the PI3K/Akt pathways. The PI3K/Akt pathway, which is negatively regulated by PTEN, contributes to stem cell self-renewal, survival and differentiation. However, the mechanism by which the PI3K/Akt pathway influences hESC pluripotency and differentiation remains unknown. We hypothesize that the PI3K/Akt pathway plays a role in maintaining hESC pluripotency, in part by regulating the expression of pluripotency genes. To test our hypothesis, we generated a knockdown of PTEN in hESCs (PTEN KD hESCs), which results in the activation of the PI3K/Akt pathway. We are using real time PCR and Western blot assays to compare the gene and protein expression profiles of PTEN KD and control hESCs. Our preliminary results suggest that the PI3K/Akt/PTEN pathway regulates pluripotency by maintaining expression of pluripotency genes.

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Ms. Jessica Jimenez
Mentor
: Dr. Carlos Portera-Cailliau
Title: Fate of Cajal-Retzius Neurons in the Postnatal Mouse Neocortex

Jessica is a fourth year neuroscience major, and began working in the laboratory of Dr. Carlos Portera-Cailliau in fall of 2008. She is a second year MARC student, and is currently applying to MD PhD programs to pursue graduate research in neurology. The laboratory currently studies the mechanisms by which cortical circuits are assembled in the brain during development. The project Jessica is currently involved in focuses on Cajal-Retzius (CR) neurons, which are known to play a crucial role in neuronal migration through the secretion of reelin.

In mice, after cortical layers are properly assembled, CR neurons gradually disappear for reasons that are still not clear to date. Still, a fraction of these neurons remain in Layer 1 into adulthood and continue to extend axons. Therefore, some CR neurons may have other functions in brain development, perhaps playing a role in the structural maturation of pyramidal neurons and their integration into functional cortical circuits. To examine the fate of CR neurons during postnatal mouse development, a transgenic Ebf2 mouse line that expresses the green fluorescent protein (GFP) only in CR neurons can be used. Utilizing two-photon imaging and electrophysiological techniques, Jessica works to begin characterizing surviving CR neuron morphological and electrophysiological properties. If surviving CR neurons do in fact have other functions in the development of the cortical circuit, a comparison between these characteristics at early and adult time points will provide insight needed to begin making inferences about those functions.

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Ms. Jacqueline Kimmey
Mentor: Dr. Marcus Horwitz
Title: Iron Acquisition via Hemin in Mycobacterium tuberculosis


Jacqueline Kimmey is a fourth year Microbiology, Immunology, and Molecular Genetics major.  She is a senior MARC trainee and will be graduating in spring 2011. She starting working in the Horwitz lab in June 2009, in the department of Medicine, Division of Infectious Diseases.  

She is currently working to identify the genes responsible for a secondary iron acquisition system in the human pathogen Mycobacterium tuberculosis.  She is continuing her work this summer (2010) in the lab, and is very excited about the progress that she has made. She hopes to present at the Keystone meeting on Tuberculosis in January 2011. 

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Mr. Rey Martin
Mentor: Dr. Sabeeha Merchant
Research Title: Proteomic and Genetic Analysis of the Zinc Nutrition Response of Chlamydomonas

Dr. Sabeeha Merchant, Rey Martin, Dr. Davin Malasarn

Rey Martin is a third year biochemistry major and biomedical research minor. He is a first year MARC student, and the biochemistry lab he works in is interested in the mechanisms eukaryotic cells use to maintain trace metal homeostasis. He joined Dr. Merchants’s laboratory fall quarter of his sophomore year and works under the supervision of the postdoctoral researcher, Dr. Davin Malasarn. He has also participated in PEERS and CARE Scholars and plans to go on to a Ph.D. program after college.

In many organisms, zinc is the most abundant transition metal because it functions as a cofactor in a number of enzymes. However, a high concentration of zinc in cells is detrimental to the organism, making it necessary to maintain zinc homeostasis. The mechanisms contributing to homeostasis in eukaryotic cells are not completely understood and so is a subject of research interest. Responses to zinc-deficiency are being studied using the unicellular green alga, Chlamydomonas reinhardtii. For growth in zinc-deficient medium, Chlamydomonas requires the CRR1 gene, previously identified as a copper response regulator. From a previous screen, suppressors of the crr1 phenotype were identified. These strains (called mutants or revertants) grow like the wild-type strain under zinc-deficient conditions. However, unlike the wild-type strain, the mutants constitutively express plastocyanin, a copper dependent protein normally degraded in zinc-deficiency. These mutants can also grow like the wild-type strain under copper-deficiency and are being analyzed for the copper-dependent expression of plastocyanin. The mutants are being placed into complementation groups to assess the number of affected loci and to test the linkage between the original mutation in CRR1 and the new suppressor mutation. Another physical response of wild type cells in zinc-deficiency is the formation of spherical bodies that contain biounavailable copper. Spectroscopy was used to determine that the crr1 mutants also accumulate copper. Copper hyperaccumulation is also observed in all of the revertants. Strains containing the crr1 mutation were stained with CS3, a copper dye, and imaged microscopically. The data obtained suggests the formation of copper granules is CRR1 independent. The proteome of C. reinhardtii is also being studied by comparing the proteins expressed in zinc-replete and zinc-deficient conditions in wild type cells using mass spectroscopy. The soluble protein samples have been prepared and the proteins that accumulate differently in the two conditions will be identified with reference to the proteome derived from the sequenced genome. The results from these studies will provide more information on the pathways necessary for eukaryotes to maintain zinc homeostasis.

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Mr. Guillermo Milian
Mentor: Dr. Stephanie White
Project: Modeling Human Autism and Language Impairment Through Developmental Expression of Protein Cntnap2 in Zebra Finches

Guillermo Milian is an entering junior majoring in Integrative Biology & Physiological Science. As an entering MARC trainee he joined Dr. Stephanie White's lab where he is investigating the role's of an autism susceptibility gene in zebra finches. From cellular to behavioral analyses in finches, it is expected to establish a better understanding of human language disorders. Prior to joining MARC and Dr. White's lab, Guillermo was a part of the CARE Fellows/Scholars Program. He spent a year in Dr. Minor's lab determining whether glucose administration following administered stress enhanced rats' ability to develop resilience. He looks forward to applying to PhD programs in Immunology to learn more about the body's defense against disease.

Autism Spectrum Disorder (ASD) is characterized by impairments in communication, social interactions, and behavior.  Mutations in contactin associated protein-like 2 (Cntnap2) are associated with ASD and specific language impairment (SLI). Since songbirds share their vocal learning phenotype and analogous neural circuitry with humans they are a preferred model for studying language disorders. Elevated mRNA expression of Cntnap2 in the frontal cortex of developing human brains suggests that Cntnap2 is involved in stenciling circuits that are involved in cognition and language. In this study, we track the expression of protein Cntnap2 in several song nuclei in zebra finches at key developmental stages through immunohistochemical analysis. Preliminary results have shown sexually dimorphic expression of Cntnap2 within song nuclei. In males, Cntnap2 is enriched in the robust nucleus of the arcopallium (RA) and lacking in basal ganglia nucleus area X throughout development. In females, Cntnap2 is enriched in RA early in development but wanes with age.

Additionally, through double labeling with synaptic vesicle protein 2 (SV2), we will investigate whether Cntnap2 is localized to synapses in RA.  This will ascertain whether Cntnap2 signal in RA is a product of RA or LMAN cell bodies. The source of Cntnap2 will then be the target for in vivo viral injections of Cntnap2 knockdown constructs, which will then allow us to study changes in neural electrophysiology and in behavior. Establishing the roles of Cntnap2 would allow for better understanding and more effective approaches towards ASD and SLI.

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Mr. Matt Pimentel
Mentor: Dr. Lily Wu
Title: Macrophages Promote Stress-Enhanced Breast Cancer Metastasis

Vice Provost Judith Smith and Matt Pimentel

Matt Pimentel is a 4th year MIMG major, hailing from Hemet, CA. He is a second year MARC student, working in the Department of Molecular & Medical Pharmacology under the direction of Lily Wu. He is currently investigating the role of macrophage colony stimulating factor in immunosuprression. Matt's research career began during the fall quarter of his second year when he found a research project in Steve Cole's lab through the SRP website. Since then, with the support of the URC/CARE cohort, he has received the CARE Fellowship, spent the summer of 2009 at the University of Texas, Marine Science Institute, attended the SACNAS and CAMP conferences, and participated in immunology research at the University of Pennsylvania. Matt will be applying to PhD programs in Fall 2010, and hopes to land in a lab studying immunology or an awesome infectious disease.

Pathological inflammatory conditions such as cancer result in the systemic accumulation of myeloid-derived suppressor cell (MDSC). MDSCs are a heterogeneous population of macrophage-like and neutrophil-like cells with an immunosuppressive phenotype, resulting in T-cell suppression and immune tolerance to solid tumors. Recent clinical and experimental studies suggest that tumor-derived factors such as stem-cell factor (SCF), IL-6, and macrophage colony stimulating factor (CSF-1) promote MDSC accumulation. CSF-1 has recently been shown to induce an anti-inflammatory phenotype in macrophages, however the mechanisms by which this factor modulates MDSC function in tumors remains to be elucidated. The present study will examine the role of CSF-1 in promoting immunosuppressive macrophages in vitro. We hypothesize that treatment of bone marrow-derived macrophages with CSF-1 alone will induce T-cell suppressive macrophages, and will further enhance the immunosuppressive activity of the anti-inflammatory cytokine IL-4. Results from these studies will establish whether the immunosuppressive activities of MDSCs are CSF-1-dependent and provide a basis for new interventions that target CSF-1 as a mediator of immune evasion by solid tumors.

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Mr. Ryan Quiroz
Mentor: Dr. Yung-Ya Lin
Title: Targeted Magnetic Resonance Imaging of Pancreatic Cancer through Antibody-Conjugated Nanoparticles

Ryan Quiroz is a third year student majoring in Biochemistry.  He is a first year MARC student currently working in a physical chemistry lab researching the early detection of pancreatic cancer with magnetic resonance imaging via antibody-conjugated magnetic nanoparticles.  He has been a CARE SEM SPUR participant, as well as a CARE Scholar, and plans to apply to a PhD program in pharmacology.  He has been with this lab since 2008 under the mentorship of his P.I. Dr. Yung-Ya Lin.

Cancer is now the leading cause of death worldwide, with pancreatic cancer being the hardest to diagnose and treat.  Nonetheless, promise for the mitigation of pancreatic cancer comes from early detection through magnetic resonance imaging (MRI).  Currently, real hope for abating and fighting this cancer comes from this detection of small, localized tumors, where the cancer can then be surgically removed.  Also, due to the fact that pancreatic cancer can exhibit resistance to chemo- and radiotherapy, detecting this malignancy at the earliest possible stage will increase not only the treatment options available but also the survival rate of the patient.  This detection can be accomplished using antibody-conjugated Superparamagnetic Iron Oxide (SPIO) nanoparticles capable of binding to these pancreatic cancer cells.  These SPIO nanoparticles have an intrinsic magnetic field, shortening the T2 relaxation time of the net transverse magnetization of surrounding water protons, providing negative contrast in the MR image.  The enhanced contrast is then used to visually assess the distribution and magnitude of the tumor cells.  In order to test the viability and efficiency of antibody-conjugated nanoparticles, anti-CA 19-9 antibodies were incubated with 25 nm NH2-PEG-coated SPIO nanoparticles, utilizing reductive amination chemistry for the coupling.  SPIO conjugation was analyzed through particle size determination and protein assay, and cell binding was verified through Prussian Blue iron staining.  Optical and in vitro MR images of the cells were also taken for sensitivity and specificity measurements.  Ultimately, the conjugation of antibodies to SPIO provides a platform for future research in cancer molecular imaging.  

 

Profiles of Students