The eSpCas9 mRNA expresses enhanced-specificity SpCas9 protein (sequence reference: Slaymaker et al Science. 2015 Dec 1). eSpCas9 can reduce off-target effects by over 10-fold, while maintaining robust on-target genome editing efficiency. This mRNA is capped with Cap1 structure with high capping efficiency. It has 100% substituted with 5-methoxyuridine for enhanced expression and reduced immunogenicity. The mRNA has a 100A tail in its sequence, mimics a mature mRNA.