Mariano Garcia-Blanco, MD, PhD
Charles D. Watts Professor
Director, Center for RNA Biology

Human and viral genes are complex units of information whose tightly regulated expression produces a dazzling array of phenotypes. The Garcia-Blanco laboratory focuses on gene expression from the perspective of RNA biology. The laboratory studies gene expression in three biological contexts of biomedical importance: 1) Infection of human and insect cells with flaviviruses such as dengue and yellow fever viruses, 2) epithelial-mesenchymal transitions among carcinoma cells and 3) multiple sclerosis. 

1. Human and insect host factors important for flaviviruses.
Flaviviruses are a major health problem in the tropics and represent an emerging danger to global health. This threat was loudly announced by the North American West Nile virus epidemic, and recent Dengue outbreaks in France and the US.  Comparatively little is known about the molecular biology of these viruses, and the Garcia-Blanco laboratory is identifying host factors, both insect and human, required for infection with pathogenic flaviviruses using en masse approaches. Given that these viruses live in an RNA world, never using DNA as genetic material, many of these host factors are RNA binding proteins.  The work on flaviviruses is carried out at Duke University School of Medicine and at the Duke-NUS Graduate Medical School in Singapore.   

2. Alternative splicing regulation during epithelial-mesenchymal transitions in cancer.
In the great majority of human transcripts, protein coding information is found in short exons that are identified and ligated together in the process known as pre-messenger RNA splicing. The complex nature of genes provides for versatility of expression because one gene can encode for many proteins by altering the selection of exons to be included in the messenger. This process is known as alternative splicing, and it is the major engine of proteome diversity in humans. The laboratory has pioneered the use of reporter constructs to image alternative splicing decisions in vivo, both in normal tissues in transgenic mice and in syngeneic prostate tumors in rats. In the latter system, imaging of alternative splicing has led to the unexpected discovery of epithelial plasticity (epithelial-mesenchymal and mesenchymal-epithelial transitions) in tumors presumed to be anaplastic. These transitions appear to be essential for tumor progression and the development of metastases, the major cause of morbidty and mortality in cancer patients.  This has led to a reevaluation of the importance of a plasticity phenotype in tumor fitness. A major focus of the laboratory is the determination of the signaling pathways that mediate alternative splicing changes during epithelial-mesenchymal transitions in cancer. Furthermore, this work in animal model systems has inspired a collaborative effort with Dr. Andrew Armstrong (a medical oncologist at the Duke Prostate Center) to detect plasticity in human prostate tumors and in circulating cancer cells.
 
3. Alternative splicing of IL-7Ralpha in multiple sclerosis.  In collaboration with Dr. Simon Gregory, we showed that a SNP associated with increased risk of multiple sclerosis was important in the regulation of the alternative splicing of IL-7 receptor alpha subunit transcripts. This receptor is critical for Tcell ontogeny and function, which are intimately linked to the development of multiple sclerosis. The alternative splicing affected by the SNP determines the ratio of soluble vs membrane bound receptor in Tcells by differential inclusion of exon 6. We are characterizing the cis-elements and trans-acting factors that regulate inclusion of this exon. These studies should provide further insights into this poorly understood syndrome.