Researchers at Rice University have evolved compact Cas9 enzymes using artificial intelligence-supported Sequence Display technology, successfully targeting previously inaccessible DNA stretches in coronary heart disease genes as published in Nature Communications.
Engineered Proteins Target Stubborn DNA Docking Stations
- Targeting Hard-to-Reach DNA: The newly evolved CRISPR proteins can dock onto stubborn DNA docking stations called PAMs that older tools slipped off of.
- Fighting Heart Disease Genes: Scientists used these enhanced enzymes to precisely edit specific sites within the APOC3 and PCSK9 genes linked to coronary heart disease risks in cultured cells.
- Rapid Laboratory Discovery: The AI-driven Sequence Display platform allowed the research team to find promising enzyme variants within a single week.
Expanding CRISPR Access with AI and Sequence Display
CRISPR/Cas9 relies on specialized enzymes that attach to short stretches of DNA known as protospacer adjacent motifs, or PAMs. These segments function as biological docking stations, dictating precisely where the enzyme can make its cuts. Many high-value therapeutic targets feature slippery or elusive PAMs that standard Cas9 tools struggle to bind effectively. To overcome this structural barrier, Rice University chemist Han Xiao utilized an AI-supported platform called Sequence Display to rapidly generate large datasets and identify optimal protein variants.
Working alongside graduate student and first author Linqi Cheng, the research team focused on a compact enzyme variant known as SlugCas9. While SlugCas9 handles various docking sequences, it routinely slipped off four specific PAM sites of major biomedical interest. Past attempts by various laboratories to evolve enzymes capable of binding these specific stubborn locations met with limited success because directing protein evolution precisely is exceptionally difficult. Using Sequence Display, Xiao’s laboratory isolated promising candidates within a single week without changing the underlying target genes.
Targeting Coronary Heart Disease Pathways
Once the team evolved the enhanced SlugCas9 variants, they tested the platform on disease-linked targets. They focused specifically on the APOC3 and PCSK9 genes, both of which are linked to coronary heart disease risk. Prior versions of the compact CRISPR tool failed to bind reliably to the exact genetic locations researchers needed to reach for therapeutic intervention.
With the newly evolved SlugCas9, the team successfully edited these challenging sites in cultured cells. The procedure introduced protective genetic modifications associated with a reduced risk of coronary heart disease. This proof-of-concept study demonstrates that rapid AI-driven enzyme evolution can unlock complex genetic targets that previously resisted standard gene editing approaches.
| Research Element | Standard SlugCas9 | Evolved SlugCas9 |
|---|---|---|
| Target Binding Efficiency | Weak on four specific PAMs | High efficiency on previously elusive PAMs |
| Discovery Timeline | Prior attempts met with little success | Identified within one week via Sequence Display |
| Tested Disease Genes | Inaccessible at key APOC3/PCSK9 sites | Successfully edited in cultured cells |
Financial support for this study came from the SynthX Seed Award, the National Institutes of Health, the Robert A. Welch Foundation, the U.S. Department of Defense, the Rice Synthetic Biology Institute Seed Grant, and a Medical Research Award from the Robert J. Kleberg Jr. and Helen C. Kleberg Foundation.
References
- Nature Communications: Research on Sequence Display technology and evolved compact Cas9 variants by Rice University investigators.
- National Institutes of Health (NIH): Grant support details under awards R35-GM133706, R01-CA277838, and R01-AI165079.
