CRISPR-induced exon skipping is dependent on premature termination codon mutations

Abstract

In previous studies, CRISPR/Cas9 was shown to induce unexpected exon skipping; however, the mechanism by which this phenomenon is triggered is controversial. By analyzing 22 gene-edited rabbit lines generated using CRISPR/Cas9, we provide evidence of exon skipping at high frequency in premature termination codon-mutated rabbits but not in the rabbits with a premature termination codon mutation in exon 1 rabbits with non-frameshift or missense mutations. Our results suggest that CRISPR-mediated exon skipping depends on premature termination codon mutation-induced nonsense-associated altered splicing.

Keywords: CRISPR/Cas9; Exon skipping; PTC; Rabbits.

Fig. 1

Exon skipping induced using the CRISPR/Cas9 system. a No exon skipping in rabbits with a non-frameshift mutation. b Non-frame shift mutation in exon 6 of GCK did not induce exon skipping. Schematic diagram of sgRNA target site in exon 3 of the rabbit GCK gene locus and RT-PCR analysis of GCK gene-editing rabbits for exons 2, 3, 4 and 5. Gel images have been cropped. M, which shows the DL2000 ladder, indicates band size. K1, K2, K3, the GCK gene-edited rabbits used in this study. c CRISPR-mediated exon skipping depends on PTC mutation-induced nonsense-associated altered splicing (NAS). d PTC mutation in exon 12 of ANO5 gene induces exon skipping. Schematic of sgRNA target site in exon 12 of the rabbit ANO5 gene and RT-PCR analysis of ANO5 gene-editing rabbits for exons 10, 11, 12, 13 and 14. Gel images have been cropped. M, which shows the DL2000 ladder, indicates band size. A1-A2, the ANO5 gene-edited rabbits used in this study. e No exon skipping in mutated rabbits with a PTC in exon 1. Rectangle, exon; blue octagon, normal stop codon; red octagon, PTC; NMD, nonsense-mediated decay; NAS, nonsense-associated alternative splicing; ATG, initiation codon; E1-E5, different exons. (F) PTCs mutation in exon 1 of MSTN gene did not induce exon skipping. Schematic diagram of sgRNA target site in exon 1 of the rabbit MSTN gene locus and RT-PCR analysis of MSTN gene editing rabbits for exons 1, 2 and 3. Gel images have been cropped. M, which shows the DL2000 ladder, indicates band size. M1, M2, M3, the MSTN gene-edited rabbits used in this study