Table 1.

Kinetic analysis of β-galactosidase-expressing cells in flk-1^+/+, +/−, and −/− EBs

Exp		D2.75	D4	D6	D9
1	flk-1+/−	3.3		31.97	18.83
	flk-1−/−	4.6		47.26	18.75
2	flk-1+/−	3.9	18.9	23.9
	flk-1−/−	2.8	19.0	24.3

β-galactosidase-expressing cells were stained with FDG and quantified by FACS. The % of β-galactosidase-expressing cells present in day 2.75-9 EBs in two separate representative experiments is shown. The percentage of β-galactosidase-expressing cells in flk-1^+/− EBs was similar to that of Flk-1-expressing cells as judged by Flk-1 monoclonal antibody staining (ref. 20, not shown).