Sdf1a overexpression can retain HSPCs in the VDA. (A-B) Still image sequences extracted from time-lapse confocal microscopic recording of the VDA region of Tg(cd41:eGFP) embryos mosaicly expressing mCherry alone (A control) and mCherry plus Sdf1a (B Sdf1a overexpression). The corresponding videos were shown in supplemental Video 3 (control) and supplemental Video 4 (Sdf1a overexpression). Yellow arrows identify the VDA localized Cd41-eGFP⁺/mCherry⁺ HSPCs that are trapped in Sdf1a overexpression embryos (B) but released in control embryos (A). Of note, in Sdf1a overexpression embryos (B), Cd41-eGFP⁺ HSPCs without Sdf1a overexpression were also released from the VDA (white arrows). (C) Quantification of the percentage of exited Cd41-eGFP⁺/mCherry⁺ cells in Tg(cd41:eGFP) embryos mosaicly overexpressing mCherry plus sdf1a (Sdf1a overexpression) and mCherry alone (control) in a 12-hour recording (n ≥ 19, mean ± SD). An asterisk indicates a statistical differences with embryos mosaicly overexpressing mCherry alone (t test, P < .05).