The Splicing Factor

The uptake and destruction of bacteria by phagocytic cells is an essential defense mechanism in metazoans. To identify novel genes involved in the phagocytosis of Staphylococcus aureus, a major human pathogen, we assessed the phagocytic capacity of adult blood cells (hemocytes) of the fruit fly, Drosophila melanogaster, by testing several lines of the Drosophila Genetic Reference Panel. Natural genetic variation in the gene RNA-binding Fox protein 1 (Rbfox1), also known as Rbfox1, correlated with low phagocytic capacity in hemocytes, pointing to Rbfox1 as a candidate regulator of phagocytosis. Loss of Rbfox1 resulted in increased expression of the Immunoglobulin-superfamily member Down syndrome adhesion molecule 4 (Dscam4). Silencing of Dscam4 in Rbfox1-depleted blood cells rescued the fly’s cellular immune response to S. aureus indicating that downregulation of Dscam4 by Rbfox1 is critical for S. aureus phagocytosis in Drosophila. This study is the first to demonstrate a link between Rbfox1, Dscam4, and host defense against S. aureus.