Question: Which is the mechanism used for synthesis of a highly functional N-truncated dystrophin isoform that attenuates dystrophinopathy?

Context:
Translation from a DMD exon 5 IRES results in a functional dystrophin isoform that attenuates dystrophinopathy in humans and mice
amelioration of disease severity has been shown to result from alternative translation initiation beginning in DMD exon 6 that leads to expression of a highly functional N-truncated dystrophin. Here we demonstrate that this isoform results from usage of an internal ribosome entry site (IRES) within exon 5 that is glucocorticoid inducible
However, amelioration of disease severity has been shown to result from alternative translation initiation beginning in DMD exon 6 that leads to expression of a highly functional N-truncated dystrophin.
Translation from a DMD exon 5 IRES results in a functional dystrophin isoform that attenuates dystrophinopathy in humans and mice.
We generated a truncated reading frame upstream of the IRES by exon skipping, which led to synthesis of a functional N-truncated isoform in both human subject-derived cell lines and in a new DMD mouse model, where expression of the truncated isoform protected muscle from contraction-induced injury and corrected muscle force to the same level as that observed in control mice.
However, amelioration of disease severity has been shown to result from alternative translation initiation beginning in DMD exon 6 that leads to expression of a highly functional N-truncated dystrophin
We generated a truncated reading frame upstream of the IRES by exon skipping, which led to synthesis of a functional N-truncated isoform in both human subject-derived cell lines and in a new DMD mouse model, where expression of the truncated isoform protected muscle from contraction-induced injury and corrected muscle force to the same level as that observed in control mice
However, amelioration of disease severity has been shown to result from alternative translation initiation beginning in DMD exon 6 that leads to expression of a highly functional N-truncated dystrophin. 
We generated a truncated reading frame upstream of the IRES by exon skipping, which led to synthesis of a functional N-truncated isoform in both human subject-derived cell lines and in a new DMD mouse model, where expression of the truncated isoform protected muscle from contraction-induced injury and corrected muscle force to the same level as that observed in control mice. 
However, amelioration of disease severity has been shown to result from alternative translation initiation beginning in DMD exon 6 that leads to expression of a highly functional N-truncated dystrophin.
We generated a truncated reading frame upstream of the IRES by exon skipping, which led to synthesis of a functional N-truncated isoform in both human subject-derived cell lines and in a new DMD mouse model, where expression of the truncated isoform protected muscle from contraction-induced injury and corrected muscle force to the same level as that observed in control mice.
amelioration of disease severity has been shown to result from alternative translation initiation beginning in DMD exon 6 that leads to expression of a highly functional N-truncated dystrophin.
However, amelioration of disease severity has been shown to result from alternative translation initiation beginning in DMD exon 6 that leads to expression of a highly functional N-truncated dystrophin.
Translation from a DMD exon 5 IRES results in a functional dystrophin isoform that attenuates dystrophinopathy in humans and mice.

Answer: Translation from a DMD exon 5 IRES results in a functional dystrophin isoform that attenuates dystrophinopathy in humans and mice
Alternative translation initiation beginning in DMD exon 6 with the use of an internal ribosome entry site (IRES) within exon 5 that is glucocorticoid inducible leads to expression of a highly functional N-truncated dystrophin isoform which is able to ameliorate disease severity.
Translation from a DMD exon 5 IRES results in a functional dystrophin isoform that attenuates dystrophinopathy in humans and mice