rbm24a and rbm24b are required for normal cardiac development. Translation blocking morpholinos complementary to rbm24a (5 ng) or rbm24b (8 ng) were injected into 1-2 cell stage zebrafish embryos and the resulting phenotypes were evaluated compared to uninjected controls at 48 hpf (A, B, D), 72 hpf (F,G,I), and 96 hpf (K, L, O). Lateral heart views are shown with a dotted outline around the heart chambers. Both morphant embryo conditions exhibited cardiac looping defects and edema at all stages. Heart chambers are shown with a dotted outline with chambers denoted: v, ventricle; a, atrium; black arrows, cardiac edema. Phenotype rescue was achieved for each rbm24 via co-injection of each respective full length capped poly-A RNA transcript (rbm24a 800 pg, rbm24b 50 pg) along with the respective complementary translation blocking morpholino into 1-2 cell stage embryos where 800 pg rbm24a (C, H, M) or 50 pg rbm24b (E, J, P) achieved rescue. Rescued embryos posses looped hearts absent of edema.