title: Topoisomerase inhibitors unsilence the dormant allele of Ube3a in neurons.
abstract: Angelman syndrome is a severe neurodevelopmental disorder caused by deletion or mutation of the maternal allele of the ubiquitin protein ligase E3A (UBE3A). In neurons, the paternal allele of UBE3A is intact but epigenetically silenced, raising the possibility that Angelman syndrome could be treated by activating this silenced allele to restore functional UBE3A protein. Using an unbiased, high-content screen in primary cortical neurons from mice, we identify twelve topoisomerase I inhibitors and four topoisomerase II inhibitors that unsilence the paternal Ube3a allele. These drugs included topotecan, irinotecan, etoposide and dexrazoxane (ICRF-187). At nanomolar concentrations, topotecan upregulated catalytically active UBE3A in neurons from maternal Ube3a-null mice. Topotecan concomitantly downregulated expression of the Ube3a antisense transcript that overlaps the paternal copy of Ube3a. These results indicate that topotecan unsilences Ube3a in cis by reducing transcription of an imprinted antisense RNA. When administered in vivo, topotecan unsilenced the paternal Ube3a allele in several regions of the nervous system, including neurons in the hippocampus, neocortex, striatum, cerebellum and spinal cord. Paternal expression of Ube3a remained elevated in a subset of spinal cord neurons for at least 12  weeks after cessation of topotecan treatment, indicating that transient topoisomerase inhibition can have enduring effects on gene expression. Although potential off-target effects remain to be investigated, our findings suggest a therapeutic strategy for reactivating the functional but dormant allele of Ube3a in patients with Angelman syndrome.
authors.affiliation: Department of Cell and Molecular Physiology, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA.
authors.forename: Hsien-Sung
authors.initials: HS
authors.lastname: Huang
authors.forename: John A
authors.initials: JA
authors.lastname: Allen
authors.forename: Angela M
authors.initials: AM
authors.lastname: Mabb
authors.forename: Ian F
authors.initials: IF
authors.lastname: King
authors.forename: Jayalakshmi
authors.initials: J
authors.lastname: Miriyala
authors.forename: Bonnie
authors.initials: B
authors.lastname: Taylor-Blake
authors.forename: Noah
authors.initials: N
authors.lastname: Sciaky
authors.forename: J Walter
authors.initials: JW
authors.lastname: Dutton
authors.forename: Hyeong-Min
authors.initials: HM
authors.lastname: Lee
authors.forename: Xin
authors.initials: X
authors.lastname: Chen
authors.forename: Jian
authors.initials: J
authors.lastname: Jin
authors.forename: Arlene S
authors.initials: AS
authors.lastname: Bridges
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Zylka
authors.forename: Bryan L
authors.initials: BL
authors.lastname: Roth
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Philpot
mesh_terms: D000483:Alleles; D017204:Angelman Syndrome / Q000188:drug therapy / Q000235:genetics; D000818:Animals; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D004353:Drug Evaluation, Preclinical; D005220:Fathers; D005260:Female; D020868:Gene Silencing / Q000187:drug effects*; D018392:Genomic Imprinting / Q000187:drug effects / Q000235:genetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009035:Mothers; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism*; D054852:Small Molecule Libraries / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology; D059003:Topoisomerase Inhibitors / Q000008:administration & dosage / Q000032:analysis / Q000493:pharmacokinetics / Q000494:pharmacology*; D019772:Topotecan / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology; D044767:Ubiquitin-Protein Ligases / Q000172:deficiency / Q000235:genetics*
chemical_list: D054852:Small Molecule Libraries; D059003:Topoisomerase Inhibitors; D019772:Topotecan; C502429:Ube3a protein, mouse; D044767:Ubiquitin-Protein Ligases