A prp1 Morpholino injected into zebrafish with mutated prp1 caused significant phenotype at a dose of 6 ng/embryo but had little effect at lower doses (see Supplemental Figure S13). This is a case where the Morpholino-in-mutant experiment not only detected an off-target interaction of the Morpholino but defined a dose where the effect suddenly became strong. Doses of prp1 Morpholino below that threshold produced phenotype at roughly the rate of the standard control oligo injections.
Leighton PLA, Kanyo R, Neil GJ, Pollock NM, Allison WT. Prion gene paralogs are dispensable for early zebrafish development but have non-additive roles in seizure susceptibility. J Biol Chem. 2018 Jun 14. pii: jbc.RA117.001171. doi: 10.1074/jbc.RA117.001171. [Epub ahead of print]