Search-and-replace genome editing without double-strand breaks or donor DNA
Anzalone et al. (2019) introduce prime editing: a catalytically impaired Cas9 (H840A nickase) fused to an engineered reverse transcriptase (MMLV RT), programmed by a prime editing guide RNA (pegRNA) that both directs Cas9 to the target and encodes the desired edit as an RT template. The system makes no double-strand breaks and requires no donor DNA template, enabling all 12 types of point mutation plus insertions and deletions. Over 175 edits were demonstrated in human cell lines; the technology was confirmed in post-mitotic primary mouse cortical neurons at 7.1% efficiency — the foundational lower bound for h07’s OHC efficiency extrapolation.
Key finding
PE3 in primary post-mitotic mouse cortical neurons: 7.1% average prime editing at DNMT1 in sorted GFP+ nuclei, 0.58% indels (PMC6907074 Fig 5d). This is the quantified neuronal baseline that h07 uses. The h07 note previously said “low frequency, no number given” — that undercharacterizes the published data.
Numbers that matter
| Parameter | Value | Units | Source | Conditions |
|---|---|---|---|---|
| Cortical neuron PE efficiency (sorted) | 7.1 | % | PMC6907074 Fig 5d | Primary post-mitotic mouse CX, DNMT1 locus, PE2 + lentiviral delivery, GFP+ sorted nuclei |
| Cortical neuron indel rate | 0.58 | % | PMC6907074 Fig 5d | Same conditions |
| Total edits demonstrated | >175 | count | Abstract | Human cell lines + primary neurons |
| Edit classes enabled | 12 | types | Abstract | All point mutations + indels |
| HEK293T typical PE3 efficiency | 20–50 | % | Paper | Cell line; no division requirement |
| PegRNA structure | spacer + RT template + PBS | — | Paper | PBS 3’ extension; RT template encodes desired edit |
Limitations
- 7.1% is in sorted GFP+ nuclei (enriched population). Unenriched efficiency is lower.
- Lentiviral delivery in neurons; in vivo AAV split-PE not yet developed (see Davis 2024).
- PE2 used; PE3/PE3b/PE4 are later improvements with higher efficiency.
- No OHC or cochlear data; OHC post-mitotic status makes them a predicted but unconfirmed analogue.
Connections
[source]Prime Editing for STRC — 7.1% neuron lower bound for h07 OHC efficiency range[source]STRC Cross-Hypothesis Verification Sweep 2026-04-25 — sweep confirmed 7.1% value; h07 note corrected[part-of]prime-editing — prime-editing topic parameter table[applies]h07 hub — foundational PE mechanism paper; efficiency lower bound[see-also]2024-davis-dual-aav-split-prime-editor-brain — same lab; 6× improvement on neuron PE by 2024