primeeditointi

Primeeditointi, or prime editing, is a genome editing approach derived from the CRISPR-Cas system. It enables precise base substitutions, small insertions, and deletions without creating double-strand breaks in the DNA, reducing some forms of unintended repair outcomes compared with standard CRISPR-Cas9 methods.

The method combines a Cas9 nickase enzyme (a mutated Cas9 that cuts only one DNA strand) with a reverse transcriptase enzyme. A specialized guide RNA, called a prime editing guide RNA (pegRNA), specifies both the target site and the desired edit, encoding a template for the reverse transcriptase to copy into the genome. The nick and the reverse transcription create the edited DNA sequence, which is then integrated through cellular repair processes. Some implementations, known as PE3 and its variants, introduce a second nick on the opposite strand to improve editing efficiency.

Prime editing was developed by researchers led by David Liu and reported in 2019. Since then, several iterations (PE2, PE3, and related refinements) have aimed to improve efficiency, broaden target compatibility, and reduce unintended edits. The system is designed to work across a range of cell types and organisms, and can, in principle, correct or introduce a variety of small genetic changes without requiring donor DNA templates or causing widespread double-strand breaks.

Applications of prime editing include basic research to study gene function, disease modeling, and potential therapeutic research for correcting pathogenic mutations. Limitations include variable editing efficiency depending on the genomic target and cell type, delivery challenges for in vivo use, design complexity of pegRNAs, and the need for thorough assessment of off-target effects and long-term safety. Ethical and regulatory considerations continue to shape its development and potential clinical use.