Supplementary Material for: Critical Role of the Matricellular Protein SPARC in Mediating Erythroid Progenitor Cell Development in Zebrafish

Sparc (osteonectin) is a multifunctional matricellular glycoprotein expressed by many differentiated cells. Members of this family mediate cell-matrix interactions rather than acting as structural components of the extracellular matrix (ECM); therefore, they can influence many remodelling events, including haematopoiesis. We have investigated the role of <i>sparc</i> in embryonic haematopoiesis using a morpholino antisense oligonucleotide-based knockdown approach. Knockdown of <i>sparc</i> function resulted in specific erythroid progenitor cell differentiation defects that were highlighted by changes in gene expression and morphology, which could be rescued by injection of <i>sparc</i> mRNA. Furthermore, a comparison of blood phenotypes of <i>sparc</i> and <i>fgfs</i> knockdowns with similar defects and the <i>sparc</i> rescue of the<i> fgf21</i> blood phenotype places <i>sparc</i> downstream of <i>fgf21</i> in the genetic network regulating haematopoiesis in zebrafish. These results establish a role for an ECM protein (Sparc) as an important regulator of embryonic haematopoiesis during early development in zebrafish.