PRJNA842138
Epigenetic editing alleviates Angelman syndrome phenotype in mice by unsilencing paternal Ube3a
Angelman syndrome (AS) is characterized by severe neurodevelopmental disorders due to abnormalies in maternally inherited UBE3A gene, leading to complete loss of UBE3A specifically in neurons, whereas intact paternal UBE3A is silenced by an endogenous antisense long-noncoding RNA, which is coded by UBE3A-ATS. The expression of UBE3A-ATS is regulated by the imprinting center Snrpn (Snrpn-IC) 1-3 , which is highly methylated in the maternal but not paternal allele. Recent studies using small-molecule inhibitior4, antisense oligonucleotides5, and CRISPR/Cas9-mediated AAV vector integration6 have shown that silencing of UBE3A-ATS was effective in allowing paternal UBE3A expression and alleviating AS phenotypes in mice. An potential alternative approach of silencing UBE3A-ATS is to introduce DNA methylation by epigenetic editing at the Snrpn-IC locus. Here we report that efficient DNA methylation on Snrpn-IC could be achieved by catalytically inactive Cas9 (dCas9) fused with peptide epitopes that recruit catalytic domains of two DNA methyltransferases, leading to the unsilencing of paternal Ube3a via inhibition of Ube3a-ATS expression in mouse neurons. By generating AS transgenic mice carrying the epigenetic editing system, the expression of paternal Ube3a was markedly increased and AS phenotypes in model mice were alleviated. Taken together, these results demonstrate that epigenetic editing can unsilence paternally inherited Ube3a without causing DNA sequence break, suggesting a potential therapeutic approach in AS treatment.