UBE3A and Angelman syndrome: Injection of recombinant adeno-associated viruses (rAAVs) carrying short Cas9 variant and gRNA into fetal brain (at E15) of mouse model of Angelman syndrome (AS) resulted in successful unsilencing of paternal ubiquitin–protein ligase E3A (Ube3a) throughout the brain for at least 17 months and rescued abnormal phenotypes associated with AS mice