In vitro hematopoietic and endothelial potential of flk-1−/− embryonic stem cells and embryos

In vitro hematopoietic and endothelial potential of flk-1^−/− embryonic stem cells and embryos

Departments of ^*Medicine, ^†Medical Biophysics, and the ^‡Institute of Medical Science, University of Toronto, 1 King’s College Circle, Toronto, Ontario, Canada M5G 2C4, and ^¶Department of Pathology, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8118, St. Louis, MO 63110

Communicated by Phillippa Marrack, National Jewish Medical and Research Center, Denver, CO (received for review November 5, 1998)

Abstract

Mice deficient in the Flk-1 receptor tyrosine kinase are known to die in utero because of defective vascular and hematopoietic development. Here, we show that flk-1 ^−/− embryonic stem cells are nevertheless able to differentiate into hematopoietic and endothelial cells in vitro, although they give rise to a greatly reduced number of blast colonies, a measure of hemangioblast potential. Furthermore, normal numbers of hematopoietic progenitors are found in 7.5-day postcoitum flk-1 ^−/− embryos, even though 8.5-day postcoitum flk-1 ^−/− embryos are known to be deficient in such cells. Our results suggest that hematopoietic/endothelial progenitors arise independently of Flk-1, but that their subsequent migration and expansion require a Flk-1-mediated signal.

Footnotes

↵ § These authors contributed equally to this work.
↵ ‖ To whom reprint requests should be addressed. e-mail: kchoi{at}pathology.wustl.edu.
ABBREVIATIONS:

VEGF,

vascular endothelial growth factor;

dpc,

days postcoitum;

ES,

embryonic stem;

BL-CFC,

blast colony-forming cell;

EB,

embryoid body;

LIF,

leukemia inhibitory factor;

EryP,

primitive erythroid;

RT-PCR,

reverse transcription–PCR;

FCS,

fetal calf serum;

FDG,

fluorescein di-β-d-galactopyranoside;

CDM,

chemically defined medium;

BMP-4,

bone morphogenetic protein-4;

KL,

kit ligand;

IL,

interleukin;

CSF,

colony-stimulating factor;

MTG,

monothioglycerol