Cpg15 partially rescues SMN deficiency. (A-C) Lateral-view representative images of Tg(hb9:GFP) embryos at 28 hpf uninjected (A), injected with 9 ng of smn MO (B), and injected with 9 ng of smn MO and 200 ng of full-length human cpg15 mRNA (C). (D) Full-length human cpg15 rescues motor axon defects caused by a reduction of Smn in zebrafish. Tg(hb9:GFP) zebrafish injected with 9 ng of smn MO and scored at 28 hpf using previously published criteria (29) resulted in a distribution of fish with motor nerve defects (n = 260 fish, 5,200 nerves, three injections). Coinjection of 9 ng of smn MO with 200 pg of full-length human cpg15 mRNA was able to partially rescue the nerve defects (n = 326 fish, 6,520 nerves; P < 0.01). The distribution of larval classifications (severe, moderate, mild, and no defects) was analyzed using the Mann–Whitney nonparametric rank test.