A bipartite boundary element restricts <i>UBE3A</i> imprinting to mature neurons.

Abstract

Angelman syndrome (AS) is a severe neurodevelopmental disorder caused by the loss of function from the maternal allele of <i>UBE3A</i>, a gene encoding an E3 ubiquitin ligase. <i>UBE3A</i> is only expressed from the maternally inherited allele in mature human neurons due to tissue-specific genomic imprinting. Imprinted expression of <i>UBE3A</i> is restricted to neurons by expression of <i>UBE3A antisense transcript</i> (<i>UBE3A-ATS</i>) from the paternally inherited allele, which silences the paternal allele of <i>UBE3A</i> in <i>cis</i> However, the mechanism restricting <i>UBE3A-ATS</i> expression and <i>UBE3A</i> imprinting to neurons is not understood. We used CRISPR/Cas9-mediated genome editing to functionally define a bipartite boundary element critical for neuron-specific expression of <i>UBE3A-ATS</i> in humans. Removal of this element led to up-regulation of <i>UBE3A-ATS</i> without repressing paternal <i>UBE3A</i> However, increasing expression of <i>UBE3A-ATS</i> in the absence of the boundary element resulted in full repression of paternal <i>UBE3A</i>, demonstrating that <i>UBE3A</i> imprinting requires both the loss of function from the boundary element as well as the up-regulation of <i>UBE3A-ATS</i> These results suggest that manipulation of the competition between <i>UBE3A-ATS</i> and <i>UBE3A</i> may provide a potential therapeutic approach for AS.