LYL1 is expressed in both angiogenic and quiescent adult endothelial cells. (A) Analysis of Lyl1 and Tal-1 mRNA in mouse adult tissues by qRT-PCR. Total RNA was extracted from different tissues derived from 4-week-old C57BL/6 mice (3 animals). cDNAs were amplified in triplicate by specific murine Lyl1 or Tal-1 primers and normalized to beta-Actin; means ± SD are shown. Sp indicates spleen; Lu, lung; Ao, aorta; Li, liver; Ki, kidney; Br, brain; and LN, lymph nodes. mRNA levels in spleen were arbitrarily set at 1. (B top) LYL1 expression in quiescent conditions: confluent HUVECs were maintained in either complete medium containing angiogenic factors (+A. F.) or starved in basal medium supplemented by 5% of FCS (− A. F.) for additional 24 hours. (Bottom) LYL1 expression in angiogenic conditions. Exponentially growing HUVECs were seeded into collagen I matrix and activated by the addition of PMA, VEGF, and bFGF. Total RNAs were extracted at the indicated time points. LYL1 and TAL-1 mRNA levels were assessed by qRT-PCR. cDNAs were amplified in triplicate by specific human LYL1 or TAL-1 primers and normalized to GAPDH. Each bar is the mean ± SD of mRNA levels relative to proliferating cells (set at 1) from 3 independent experiments performed in triplicate. **P < .01