Principal Investigator: Emanuela Tolosano, Co-Principal Investigator: Deborah Chiabrando This project is aimed at defining the role of the Feline Leukemia Virus, subgroup C, Receptor (FLVCR) in the pathogenesis of Diamond-Blackfan anemia (DBA). FLVCR encodes a protein that exports excess heme from cells. It has been suggested that defects in globin synthesis, perhaps as a result of ribosomal protein mutations, could result in excess heme in erythroid progenitors that would need to be exported from cells to reduce heme toxicity. Thus, FLVCR could play an important role in DBA pathogenesis. Recently, it has been reported that mice lacking FLVCR show a phenotype very close to that of DBA patients, including erythroid failure and malformations. However, no mutations in FLVCR have been found in a small subset of DBA patients. One of the goals of this study is to test additional DBA patients for mutations in FLVCR. It is possible however, that FLVCR could have a role in DBA pathogenesis without being mutated in DBA patients. Studies have shown that FLVCR is a complex gene giving rise to a number of related proteins that have different functions. Moreover, different tissues may express different forms of FLVCR protein. Given the complexity of the FLVCR gene it is possible that mutations in ribosomal protein genes could alter FLVCR expression. Therefore, this study will also focus on possible changes in FLVCR expression in cells with mutant forms of RPS19.Finally, the Tolosano laboratory will continue to study the role of different forms of the FLVCR protein in erythropoiesis.
Paul de Figuieredo, Ph.D., Assistant Professor, Texas A&M University was awarded a $43,256 grant for the project “Discovering therapeutics for DBA .” The long-term goal of this study is to develop small molecule therapeutics for Diamond Blackfan Anemia (DBA), by screening for molecules that overcome growth defects associated with decreased expression of ribosomal protein S19 in a yeast model of DBA. Yeast are remarkably versatile microorganisms that share many aspects of ribosome biology with humans. Because of their small size and ease of growth they are readily amenable to what are known as high throughput drug screens where thousands of compounds can be assessed for their effects on cell growth. The Figuieredo lab will initially screen 25,000 chemical compounds for their ability to reverse the effects of reduced expression of Rps19 on cell growth. Any compounds identified in the yeast screen will be examined for their ability to compensate for reduced expression of Rps19 in human cell lines. Dr. Figuieredo has had substantial success using a similar approach to identify lead compounds for therapeutic development in another ribosome-related bone marrow failure syndrome Shwachman Diamond syndrome (SDS).
Hanna T. Gazda, M.D. Instructor in Pediatrics Harvard Medical School was awarded $51,512 to continue her efforts to identify genes mutated in patients with DBA. Dr. Gazda has played a major role in the identification of most of the 11 known DBA genes. Her discoveries have clearly established DBA as a ribosomopathy which has helped direct research efforts on many aspects of this disease. Approximately 50% of DBA patients have mutations in one of the 11 known genes. In the remaining patients, the defective genes have evaded detection by conventional DNA sequencing. Dr. Gazda now plans to use sophisticated whole genome approaches to identify these remaining genes. The aim of this study is (1) to perform comparative genomic hybridization to search for deletions and duplications in ribosomal protein genes that could not have been picked up by DNA sequencing; (2) to perform whole exome sequencing (“next generation” sequencing) to potentially identify non-ribosomal protein genes that may be mutated in DBA. This latter approach is daunting in that 10’s of thousands of genes will need to be sequenced and analyzed for sequence changes that may be linked to patients with DBA. This project will result in a more complete picture of the genetic causes of DBA and the pathogenic mechanisms that result.