Production of Cas9 mRNA in vitro typically requires the addition of a 5´ cap and 3´ polyadenylation. A plasmid was constructed that harbored the T7 promoter followed by the EMCV IRES and a Cas9 coding region. We hypothesized that the use of the metastasis associated lung adenocarcinoma transcript 1 (Malat1) triplex structure downstream of an IRES/Cas9 expression cassette would make polyadenylation of in vitro produced mRNA unnecessary. A sequence from the mMalat1 gene was cloned downstream of the IRES/Cas9 cassette described above. An mRNA concentration curve was constructed with either commercially available Cas9 mRNA or the IRES/ Cas9/triplex, by injection into porcine zygotes. Blastocysts were genotyped to determine if differences existed in the percent of embryos modified. The concentration curve identified differences due to concentration and RNA type injected. Single step production of Cas9 mRNA provides an alternative source of Cas9 for use in zygote injections.
Keywords: Cas9; genetic modification; zygote.