Esteban Gonzalez Burchard, M.D., MPH
Professor of Medicine and Biopharmaceutical Sciences
Pharmacogenomics and Genetic Epidemiology of Pulmonary Diseases
University of California, San Francisco
Mission Bay Rock Hall
1550 - 4th Street, 5th floor,
Room 545, Box 2911
San Francisco, CA 94158
Esteban González Burchard received his M.D. degree from Stanford University School of Medicine in 1995. He completed clinical training in Internal Medicine at Harvard’s Brigham and Women’s Hospital and Pulmonary/Critical Care Medicine training at UCSF. Dr. Burchard also completed clinical research training at the Harvard School of Public Health. He joined the UCSF faculty in 2001. In 2006 he received his Master’s in Public Health from UC Berkeley. Dr. Burchard’s major academic interest centers on identifying genetic risk factors for asthma in ethnically diverse populations. In addition, Dr. Burchard co-directs the UCSF/SFGH DNA Banking Facility located at San Francisco General Hospital. The UCSF DNA Bank is a central core facility that is available to all UCSF investigators involved in translational genetic research.
It is well established that among U.S. residents of similar socioeconomic status, there is greater asthma morbidity and mortality among African Americans and Latino Americans than among Caucasians Americans. In addition, the reported rates of asthma morbidity and mortality differ strikingly among specific Latino American ethnic groups. Specifically, reported rates of asthma morbidity and mortality are higher among Puerto Rican Americans than among Mexican Americans. This is in stark contrast to the near geographic uniformity of asthma morbidity and mortality rates among African American and Caucasians. Although there are many potential explanations for this observation, including environmental and socioeconomic factors, one potential explanation is that the genetic predisposition to asthma or to greater asthma severity differs among subgroups within the Latino population. These genetic subgroups may have genetic variants (alleles) of asthma candidate genes, which may explain the variation in asthma prevalence, asthma severity and bronchodilator drug responsiveness in Latino ethnic groups.
My research interests center around identifying “ethnic-specific” genetic and biologic risk factors for asthma, asthma severity and drug responsiveness among U.S. ethnic and racial minority groups. In addition, I am interested in how race and racially specific genetic differences influence disease and response to therapies (pharmacogenetics). I work in collaboration with a multi-disciplinary team, which includes faculty with expertise in genetic epidemiology, biostatistics, clinical asthma, and pulmonary molecular and cell biology and genomics. Using tools from these disciplines, we conduct studies designed to elucidate genetic risk factors for asthma and asthma severity.
I am specifically interested in identifying biologic and genetic risk factors for asthma among Latino and African American populations. The Genetics of Asthma in Latino Americans (GALA) Study, is a multicenter international collaboration including UCSF, Harvard, Harlem Hospital, the University of Puerto Rico and INER of Mexico City. The goal of the GALA Study is to identify genetic risk factors for asthma and asthma severity among Mexican and Puerto Rican Americans, the two largest Hispanic groups in the U.S. Specifically, we are using a family based approach (Transmission/Disequilibrium Test or TDT) to identify genetic variants among asthma candidate genes. Identified variants are analyzed using the TDT to determine whether these alleles are associated with asthma and asthma severity among these populations. In addition, I am directing the GREAT Study ( G enetic R isk factors in E thnically diverse A sthmatic and T herapeutic groups). The goal of the GREAT Study is to identify ethnic specific, pharmacogenetic, and asthma associated genetic risk factors among African Americans.
I am also currently helping to develop methods to improve the application of population based genetic studies to ethnically admixed populations. Association studies are powerful approaches to identify genes, which have a modest influence on disease but are important from a public health perspective. A major limitation of this approach is that it may lead to spurious positive (or negative) associations between alleles and disease due to population stratification. However, theoretical methods have been developed to use unlinked genetic markers to adjust and statistically correct the findings from case-control association studies for population stratification.
We are presently testing and applying these approaches in three admixed populations of unrelated asthmatic cases and healthy controls. Specifically, we are using ancestry-informative genetic markers (AIMs), which have been selected to enhance the detection of stratification in these populations. Our first goal has been to determine if population stratification can be detected. A second goal is to determine whether adjustment using unlinked markers can be used to eliminate the probability of false positives due to population stratification. We will ultimately compare the power of genomically adjusted case-control studies to identify asthma candidate genes in these populations to the power of the TDT. This research is motivated by the difficulty encountered in identifying complete trios for a TDT-based study in minority populations; the single parent household rates among African Americans, Puerto Ricans and Mexicans are estimated at 70%, 60% and 38% respectively. With this project we hope to demonstrate that case-control studies for genetic risk factors may be done appropriately even in racially admixed and stratified populations. The study of asthma in Latino and African Americans may be a particularly important test case for this type of approach since these populations are known to have significant rates of population stratification.
Lastly, we are performing whole genome association and admixture mapping studies to identify genes related to asthma and drug responsiveness in Latino Americans using a novel genotyping platform developed by Affymetrix, which can screen 100,000 SNPs simultaneously in a single genotyping assay.