Phenotypic analysis of fibrillin-1 (fbn1) morphant embryos. (A) Uninjected Tg(fli1/EGFP) embryo at 31 hours after fertilization. (B) fbn1 MO–injected Tg(fli1/EGFP) embryo at 31 hours after fertilization, showing dilated caudal vein with reduced venous plexus formation (arrowheads). Frequency, 86% ± 4%; N = 45. (C) Anterior segment of an uninjected Tg(fli1/EGFP) embryo at 31 hours after fertilization. (D) fbn1 MO–injected Tg(fli1/EGFP) embryo at 31 hours after fertilization showing dilated vessels around the eye and in the head (arrowheads). (E) Two splice-site morpholinos against the fbn1 gene generate similar vascular defects at high frequency. (F) RT-PCR analysis demonstrating depletion of the endogenous fbn1 transcript in fbn1 MO–injected embryos. (G) Summary of 2 independent injection experiments. Synergy between magp1 MO and fbn1 MO in generating embryos with dilated vessels (compare column 3 with columns 1 and 2). In these experiments, 1 ng magp1 MO and 2 ng fbn1 MO were used. N indicates number of embryos scored. Original magnifications: (A-B) 5 ×; (C-D) 10 ×. (E,G) Error bars indicate SEM.