Rebbeck, Timothy R
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Publication Evaluation of Group Genetic Ancestry of Populations From Philadelphia and Dakar in the Context of Sex-Biased Admixture in the Americas(2009-11-25) Dulik, Matthew C; Stefflova, Klara; Pai, Athma A; Walker, Amy H; Schurr, Theodore G; Zeigler-Johnson, Charnita M; Rebbeck, Timothy R; Gueye, Serigne MBackground Population history can be reflected in group genetic ancestry, where genomic variation captured by the mitochondrial DNA (mtDNA) and non-recombining portion of the Y chromosome (NRY) can separate female- and male-specific admixture processes. Genetic ancestry may influence genetic association studies due to differences in individual admixture within recently admixed populations like African Americans. Principal Findings We evaluated the genetic ancestry of Senegalese as well as European Americans and African Americans from Philadelphia. Senegalese mtDNA consisted of ~12% U haplotypes (U6 and U5b1b haplotypes, common in North Africa) while the NRY haplotypes belonged solely to haplogroup E. In Philadelphia, we observed varying degrees of admixture. While African Americans have 9–10% mtDNAs and ~31% NRYs of European origin, these results are not mirrored in the mtDNA/NRY pools of European Americans: they have less than 7% mtDNAs and less than 2% NRYs from non-European sources. Additionally, there is <2% Native American contribution to Philadelphian African American ancestry and the admixture from combined mtDNA/NRY estimates is consistent with the admixture derived from autosomal genetic data. To further dissect these estimates, we have analyzed our samples in the context of different demographic groups in the Americas. Conclusions We found that sex-biased admixture in African-derived populations is present throughout the Americas, with continual influence of European males, while Native American females contribute mainly to populations of the Caribbean and South America. The high non-European female contribution to the pool of European-derived populations is consistently characteristic of Iberian colonization. These data suggest that genomic data correlate well with historical records of colonization in the Americas.Publication Genetics, Disparities, and Prostate Cancer(2005-06-20) Rebbeck, Timothy RIn 2005, more than 200,000 new cases of prostate cancer will be detected in the United States, and about 30,000 men will die from the disease. African American men are particularly hard-hit, dying from this disease at more than twice the rate of European Americans. The reasons for this racial/ethnic disparity are largely unknown, but probably involve an interaction among genetic, environmental, and social factors. This Issue Brief reviews current knowledge about the genetic basis of prostate cancer and summarizes ongoing research at Penn that investigates the role of genetics in prostate cancer treatment and outcomes.Publication Preventive Surgery is Associated with Reduced Cancer Risk and Mortality in Women with BRCA1 and BRCA2 Mutations(2010-11-22) Domchek, Susan M; Rebbeck, Timothy RWomen who have inherited mutations in the BRCA1 or BRCA2 (BRCA1/2) genes have a substantially elevated risk of developing breast and ovarian cancer. For more than 10 years, researchers have studied whether preventive surgery (to remove breasts, ovaries, and/or fallopian tubes) can reduce the cancer and mortality risk in BRCA1/2 mutation carriers. This Issue Brief summarizes the results of the latest, largest, multinational study on the effects of preventive surgery in these women. The results are consistent with earlier studies and provide strong evidence for the use of preventive surgery as an effective approach to managing this genetic risk.Publication Pilot Study: Does the White Coat Influence Research Participation?(2002-07-01) Merz, Jon F; Rebbeck, Timothy R; Sankar, Pamela; Meagher, Emma AIn health care, the white coat symbolizes professionalism, trustworthiness, and competence; it also represents power. This suggests that the wearing of a white coat could influence the decisions of potential subjects who are asked to participate in clinic-based research.