Sickle cell disease (SCD) is caused by a pathogenic hemoglobin (Hb) mutation, yet patients can have dramatically variable clinical manifestations. Here we address the genetic basis of this clinical heterogeneity. Using a systems genetics approach, we performed whole blood gene expression analysis and eQTL analysis on different clinical phenotypes in SCD patients.
Overall design
We generated whole blood gene expression profiles for 311 West-African children recruited from the National Sickle Cell Disease Centre in Cotonou, Benin which included 250 patients with varying degrees of SCD severities and 61 age-matched controls. SCD is caused by a point-mutation in the beta-hemoglobin gene that changes the normal HbAA protein into, most often, an abnormal HbSS or HbSC protein. The SCD patients recruited in the study either had HbSS or HbSC phenotypes and were categorized into different 3 clinical states based on follow-up status (Rahimy, MC, et al. Effect of a comprehensive clinical care program on disease course in severely ill children with sickle cell anemia in sub-Saharan African setting. Bood 102, 834-838. 2002). When patients are refered to the clinic, they are enrolled when they are in steady-state condition, and are labeled as entry (E). Patients followed at the SCD clinic are labeled as FU. Control patients were recruited and are labeled as C. Patients were also assigned a severity score (Sebastiani, P. et al. A network model to predict the risk of death in sickle cell disease. Blood 110, 2727-2735, 2007). Hemoglobin protein status (Hb phenotype) was confirmed for each patient using standard electrophoretic techniques. We generated genotypes for 263 of these individuals and performed principal component analysis (PCA) which identified 2 signigicant genotypic principal components (gPC1 and gPC2). Using the gene expression and genotyping data, we performed an eSNP analysis. . Gene expression data presented in this study.
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