Screening for Efficient gRNAs to Skip Exon 51 in the DMD Gene

A majority of Duchenne’s muscular dystrophy cases are caused by a frameshift mutation in the DMD gene and the deletion of exon 51 with CRISPR-Cas9 can restore the reading frame in many patients. However, there are thousands of gRNA sequences to choose from with a deletion frequency of only 2%, so which gRNAs in introns 50 and 51 are the most efficient? To test this, I designed 10 gRNAs in both introns and transfected 293T cells with these gRNAs and a CjCas9 plasmid. I harvested these cells, ran a PCR with designed surveyor primers and ran these fragments on a gel. No new bands were seen that were different from my no-gRNA control lane so the gRNAs I designed did not make an indel. I will test 2 new gRNA sequences with the same method and expect to see two bands unique to the gRNA-transfected cells. The results from my experiment will be positive controls for my mentor’s project of developing a high-throughput screening method of hDMD-targeted gRNAs. With broader and quicker gRNA screening, the CRISPR-Cas9 tool will be more efficient and used as a human medical treatment option for patients with DMD.

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