We first investigated the ESE potential of the CAAACAA sequence found in pig Smn1 exon 7 to evaluate the feasibility of constructing a pig Smn2-like model by introducing a single +6C.T mutation in the endogenous porcine Smn1 gene. We introduced the ESE region into the pSXN13 splicing reporter minigene and observed minimal inclusion of the alternative exon in the wild type construct and complete loss of inclusion when we introduced a C.T mutation analogous to the + 6T in SMN2. This demonstrates splicing enhancer activity of the altered pig ESE and further demonstrates that a C.T mutation can abrogate this activity despite the lack of an AG dinucleotide within the ESE which has previously been proposed to form an hnRNP A1 ESS in SMN2 exon 7. Therefore, in this context the pig ESE supports the ESE-loss model. When we disrupted the upstream ESS motif by an A.C mutation, the splicing pattern of the wild type pig ESE and mutant pig ESE was very similar to that of SMN1 and SMN2. However, the inclusion level of the wild type pig Smn1-like ESE construct seemed slightly lower than that of the wild type SMN1 construct, while the inclusion level of the mutant pig Smn2-like ESE construct seemed slightly higher than that of the SMN2 construct. These results can be explained by the ESE-loss/ ESS-gain model. The G.A change in the pig ESE seems to have decreased the ESE activity relative to the human SMN1 ESE sequence, but in the context of the +6C.T mutation, which completely abolishes the human SMN1 ESE activity, the activity of the gained ESS has also been decreased. Overall, the regulatory element is more neutral in the pig Smn1 gene than in human SMN1 and SMN2, although it retains some ESE activity. When we introduced pig Smn1 exon 7 with flanking regions in our SMN model minigene, we observed only a modest decrease in exon inclusion between the construct with the wild type sequence and the +6C.T mutant construct, indicating that in the native pig Smn1 gene a functional ESE is not crucial for exon 7 inclusion. We then examined pig intron 7 and found that in the region of the previously reported IVS7-ISS, there were differences between the human and pig sequence which could potentially alter binding affinity of one or both of the hnRNP A1 sites contained within the ISS motif. In fact, the motif score was decreased for the proximal hnRNP A1 site and increased for the distal site through an A.C mutation which has previously been shown to increase skipping of human SMN2 exon 7. These findings then lead us to investigate the ISS activity of the downstream region in pig Smn1 intron 7 and we found that when we inserted the human ISS into the pig context, a splicing pattern more similar to SMN2 splicing pattern was observed when we introduced the +6C.T mutation into the pig ESE sequence. When we introduced mutations previously reported to remove ISS activity, we observed exon inclusion similar to the wild type pig construct.