Role of the microRNA miR144 in haemopoiesis in vivo

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Recently a new form of gene regulation has been discovered involving small RNA molecules called microRNAs (miRNAs). Although vertebrates (like man, mouse and fish) contain many hundreds of miRNAs, the function and true gene targets of each individual miRNA are largely unknown. A better understanding the normal function and targets of miRNAs is needed so that their role in normal biology and disease development can be understood. These studies exploit the technical strengths of zebrafish, an model of increasing importance in biomedical research, to study the function of a particular miRNA, miR144, and to identify its physiological target genes. Zebrafish have several advantages for studying miRNA function - several simple methods for experimentally altering miRNA levels are standard in zebrafish but not easy in other models like mice. miR144 has been chosen because it has an expression pattern that strongly suggests a role in blood development. Blood development and zebrafish technologies are central themes of the Lieschke laboratory. Preliminary experiments in zebrafish have shown that miR144 expression can be detected in blood cells, that it is functionally active when overexpressed, that its effect can be intercepted, and that there are blood-system effects of its misexpression, particularly in mutant zebrafish with abnormalities of blood development that provide a sensitized background for such studies. These studies will describe the expression of miR144 in detail in normal and abnormal zebrafish blood development. The effects of miR144 overexpression and knock-down of expression will be studied in detail. To identify the targets of mir144, a multifaceted microarray analysis will be performed, and the validity of candidate targets suggested by this will then be systematically tested. When finished, these studies will have characterised the physiology of this new blood regulator and identified the way it exerts its effect.