 A year later, Choi showed that blast cells derived from embryonic stem (ES) cells displayed common gene expression of both hematopoietic and endothelial precursors.However, Ueno and Weissman provided the earliest contradiction to the hemangioblast theory when they saw that distinct ES cells mixed into a blastocyst resulted in more than 1 ES cell contributing to the majority of the blood islands found in the resultant embryo.Other studies done in zebrafish have more soundly indicated the existence of the hemangioblast.