1998 — 2002 |
Bejar, Rafael |
F30Activity Code Description: Individual fellowships for predoctoral training which leads to the combined M.D./Ph.D. degrees. |
Cam Kinase Ii and Learning and Memory @ University of California San Diego
DESCRIPTION (Adapted from applicant's abstract): The long-term objective of this research is to provide a clearer understanding of the molecular basis of synaptic plasticity and how this relates to learning, memory, and behavior. This is an important health-related issue because abnormal neuronal function has been implicated in the pathoetiology of several diseases including psychiatric disorders, ischemic brain injury, and Alzheimer's disease. This line of research is also relevant to age-related changes in memory function. We propose to study the mechanisms through which an overexpressed Ca2+-independent form of calmodulin-dependent kinase II (CaMKII-Asp286) disrupts both synaptic plasticity in the hippocampus and behavioral performance on spatial memory-dependent tasks. Our specific aims are (1) to determine whether calmodulin trapping by CaMKII-Asp286 is sufficient to produce the physiological and behavioral phenotype observed in mice expressing this Ca2+-independent form of CaMKII, (2) to determine if disruption of synaptic plasticity by CaMKII-Asp286 in the CA1 region of the hippocampus alone is sufficient to produce a deficit in spatial learning and memory, and (3) to identify which stage of learning and memory, either acquisition, consolidation, or recall, is sensitive to disruption by expression of the CaMKII-Asp286 transgene. These aims will be accomplished by studying the activity of CaMKII-Asp286 in vitro, by creating two new lines of transgenic mice, and by testing these and existing transgenic animals on spatial tasks. First, we plan to create a line of mice carrying a Ca2+-independent form of CaMKII that has no kinase activity in order to determine if calmodulin trapping alone can create a phenotype similar to that seen in our existing mice. Using the CRE-lox system, we will create a second line of mice which expresses the CaMKII-Asp286 only in the CA1 region of the hippocampus. Finally, the existing mice we plan to study suppress CaMKII-Asp286 expression in response to tetracycline. This will allow us to regulate at which time after learning the transgene is expressed and is capable of disrupting spatial memory.
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2012 — 2016 |
Bejar, Rafael |
K08Activity Code Description: To provide the opportunity for promising medical scientists with demonstrated aptitude to develop into independent investigators, or for faculty members to pursue research aspects of categorical areas applicable to the awarding unit, and aid in filling the academic faculty gap in these shortage areas within health profession's institutions of the country. |
Characterization of Genetic Abnormalities in Mds and Their Clinical Impact @ University of California San Diego
DESCRIPTION (provided by applicant): The candidate, Dr. Rafael Bejar, presents a 5-year career development plan that seeks to characterize the broad range of mutations present in patients with myelodysplastic syndromes while establishing an academic career as a physician scientist in the field of hematology. The specific aims of this proposal are to: (1) study a clinically annotated cohort of 439 bone marrow samples from patients with MDS to determine if the mutations they carry are associated with common clinical features of MDS and overall patient survival, (2) perform a pooled shRNA screen targeting each of the genes from the commonly deleted regions of chromosome 5q to determine which genes, when knocked down in human CD34+ hematopoietic cells, lead to clonal expansion in a stromal co-culture system, and (3) functionally characterize the mutations identified in MDS patient samples and candidate target genes from the shRNA screen to determine their effects on hematopoietic differentiation, clonal expansion, cell cycling, and apoptosis in an in vitro model system. Myelodysplastic syndromes are clonal disorders of hematopoiesis that cause inefficient blood cell production, low blood counts, and risk of progression to acute leukemia. The prognosis for patients with MDS is highly variable, with some only mildly affected while others succumb within months of diagnosis. Chromosomal abnormalities present in less than half of cases help stratify patients into risk groups, but prognosis is largely determined by clinical parameters. Patients with MDS have been shown to have acquired point mutations in the DNA of their diseased cells, however, these genetic lesions have not yet been incorporated into prognostic scoring systems. Molecular markers are needed to better classify subtypes of MDS, stratify prognostic risk in patients, and identify pathogenic mechanisms associated with the development and progression of these disorders. There is abundant evidence that genes that are somatically mutated and functional in one tumor type can play a role in other tumor types. A comprehensive analysis of known cancer genes in MDS has not been performed. In order to identify oncogenic mutations in MDS, a set of DNA primer extension/mass spectroscopic assays (collectively called OncoMap) will be used to determine which of 439 patient samples contain any of 1060 mutations in 104 known cancer genes. Tumor suppressor genes known to be mutated in MDS and other myeloid disorders will be sequenced in this cohort using the Roche/454 quantitative next-generation sequencing platform. These highly sensitive techniques will allow the detection of mutations even if samples contain a large fraction of normal cells or mutations are present in only a small subclone of diseased cells. With the help of collaborator Donna Neuberg and her team, a statistical analysis will be performed to determine if mutations are correlated with MDS phenotypes and the overall survival of patients even after known risk factors are considered. In collaboration with Dr. David Root from the RNAi Consortium at the Broad Institute, a pooled short hairpin RNA interference screen in human CD34+ hematopoietic cells will be performed. Genes from regions of chromosome 5q that are commonly deleted in patients with MDS will be targeted to determine which confer a clonal advantage when knocked down. After validation, gene targets identified in this screen and genes that are mutated in patient samples will be tested using in vitro human hematopoiesis assays to determine their effects on aspects of the MDS phenotype including blood cell development, apoptosis, cell- cycle changes, and clonal expansion. Dr. Bejar is well qualified to carry out the research outlined in this proposal. He has successfully completed a project of comparable complexity as part of his PhD thesis. His mentor, Dr. Benjamin Ebert, has experience studying the genetic basis of myelodysplastic syndromes and has published the result of short hairpin RNA interference screen that discovered RPS14 as a critical gene lost in patients with the 5q-minus syndrome subtype of MDS. Along with Dr. Ebert, Dr. Bejar has published an invited review on the genetic basis of MDS in Hematology/Oncology Clinics of North America and has a review on pathogenic mechanisms in MDS in progress for eventual publication in the Journal of Clinical Oncology. Dr. Bejar has recruited a team of outstanding mentors that that in addition to Dr. Ebert, include Dr. David Williams as a co-mentor, Dr. David Steensma as a clinical mentor, and Dr. Nancy Berliner, head of the Hematology division at Brigham and Women's Hospital, as a fourth member of his advisory committee. The advisory committee will meet, at minimum, every six months to ensure a successful scientific research program. Included in the career development plan are courses on biostatistics and genomic methods at the Harvard Medical School and School of Public Health. Successful completion the specific aims and career development plan outlined in this proposal will allow the candidate to advance his academic career as an independent investigator in the field of hematology.
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