Maternal pak4 expression is required for primitive myelopoiesis in zebrafish

► Zebrafish pak4 is required for primitive myeloid cell development. ► Maternal but not zygotic expression is required. ► Early patterning signals are not affected. ► Spatial patterning of hematopoietic domains is not affected. ► The pak4 loss of function can be mimicked by treatment with actin depolymerization drugs.