Given the importance of fetal hematopoiesis during JMML(-like MPN) development, the zebrafish Shp2D61G mutant represents a reliable and unique model for JMML-like MPN, which allows us to study hematopoietic defects caused by mutant Shp2 during the prenatal development for the first time. The gene discussed is PTPN11; the disease is myeloproliferative neoplasm.