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A heatmap showing on-target activity of SpCas9 variants against various targets, with WT-like cleavage indicated by green, no cleavage indicated by red, and intermediate cleavages in middle shades of yellow-green, yellow, and orange. The variants are ranked by activity and the targets are ranked by cleavability, with the result that the top-left corner (high activity, high cleavability) is green to show high cleavage, the bottom right corner (low activity, low cleavability) is red to show no cleavage, and an approximate staircase pattern divides the two colors. In each row, a miniaturized graph of off-target cleavage, normalized from 0 to 1, is shown. In general, these graphs show declining off-target cleavage among SpCas9 variants of lower activity. In each row, representing a particular target, one cell of the heatmap has been outlined in black to emphasize it as belonging to the target-matched variant. Each target-matched cell is the last in its row to show moderate yellow-green color rather than an orange color, indicating some on-target cleavage activity. Each target-matched variant has very low off-target cleavage.
A cartoon showing a simplified Cas9 and gRNA binding to DNA. The 3’ end of the gRNA is the scaffold sequence, bound by Cas9, where some DNA substitution is tolerated. The 20 bases on the 5’ end of the gRNA are the spacer sequence, which hybridizes with the genomic DNA, base pairing to the target strand.   The non-target strand of genomic DNA includes the same sequence as the spacer. The PAM consists of the three bases immediately 3’ of this spacer-matching sequence.  Within the gRNA spacer, the 3’ half is the seed sequence, where no DNA substitution is tolerated. The 5’ half, also the 5’ end of the entire gRNA, is the tail sequence, where DNA substitution is tolerated.
A cartoon of a prime editor with two different edit sequences. The DNA sequences are shown with one strand edited and a 5′ DNA flap, before heteroduplex resolution and DNA repair.  The first edit has an unchanged PAM. This DNA is shown connected to the prime editor by a two-way arrow, indicating that the editor can re-bind. Re-nicking is represented by scissors and would remove the newly edited DNA.  The second edit has an altered PAM. A one-way arrow leads from the prime editor to this edit, indicating that the changed PAM prevents the editor from re-binding.
Stabilizing gRNA Modifications
crisprGenotypingValidation-01.png

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