Improved bi-allelic modification of a transcriptionally silent locus in patient-derived iPSC by Cas9 nickase

• Homology directed repair (HDR)-based genome editing via selectable long flanking arm donors can be hampered by local transgene silencing at transcriptionally silent loci. Here, we report efficient bi-allelic modification of a silent locus in patient-derived hiPSC by using Cas9 nickase and a silencing-resistant donor construct that contains an excisable selection/counter-selection cassette. To identify the most active single guide RNA (sgRNA)/nickase combinations, we employed a lentiviral vector-based reporter assay to determine the HDR efficiencies in cella. Next, we used the most efficient pair of sgRNAs for targeted integration of an improved, silencing-resistant plasmid donor harboring a piggyBac-flanked puro Delta tk cassette. Moreover, we took advantage of a dual-fluorescence selection strategy for bi-allelic targeting and achieved 100% counter-selection efficiency after bi-allelic excision of the selection/counter-selection cassette. Together, we present an improved system for efficient bi-allelic modification of transcriptionally silent loci in human pluripotent stem cells.

Ämnesord

Medical and Health Sciences  (hsv)

Basic Medicine  (hsv)

Microbiology in the medical area  (hsv)

Medicin och hälsovetenskap  (hsv)

Medicinska grundvetenskaper  (hsv)

Mikrobiologi inom det medicinska området  (hsv)