Embryonic Egfl7 overexpression causes defects in the developing heart and in head and yolk sac vasculature. (A) CD31 immunostaining of whole-mount wild-type (i) and transgenic (v) embryos at E10.5. White and red lines represent the atrium (A) and ventricle (V), respectively. Original magnification ×30. CD31 immunostaining of parasagittal sections of wild-type (ii-iv) and Tie2-Egfl7 transgenic embryos (vi-viii). High-magnification images of black-boxed areas in subpanels ii and vi (iii,vii). High-magnification images of boxed areas in subpanels iii and vii (iv,viii). Original magnification ×1.25 (ii,vi), ×4 (iii,vii), and ×20 (iv,viii). Black asterisks represent reduction in traberculation; and red asterisks, branchial arch. (B) CD31 immunostaining of whole-mount embryos at E10.5. Tie2-Egfl7 transgenic embryos (iii-iv) showed abnormal endothelial aggregates (arrowheads), a decrease in the number of major cranial vessels (red dots), and increased branching (white dots) compared with wild-type littermates (i-ii). Original magnification ×60. (C) CD31 immunostaining of cross sections from wild-type (i-iv) and Tie2-Egfl7 transgenic embryos (v-viii) at E10.5. High-magnification images of black-boxed areas in subpanels i and v (ii,vi). High-magnification images of the boxed areas in subpanels iii and vii (iv,viii). Arrows indicates carotid artery (CA); and arrowheads, hemorrhaging from CA. Original magnification ×4 (i,iii,v,vii) and ×10 (ii,iv,vi,viii). (D) CD31 immunostaining of E12.5 wild-type (i-ii) and transgenic (iii-iv) yolk sacs. Arrowheads indicate vitelline vessels; and arrow, knot-like structure in vein. Quantification of vitelline vessel diameter in wild-type (□, n = 2) and transgenic (■, n = 4) yolk sacs. (v) *P < .03. Original magnification ×25.5 (i,iii) and × 41 (ii,iv). Whole-mount images were captured on Discovery V20 Stereomicroscope (Carl Zeiss) and immunohistochemistry images on the Axioplan 2 Imaging Upright Microscope (Carl Zeiss).