all animal procedures were approved by the university of north carolina at chapel hill animal care and use committee .
we used male and female ube3a - yfp knockin mice , ube3a mice , and their age - matched , wild - type controls .
ube3a - yfp was detected for drug screening with an anti - gfp antibody ( novus biologicals , nb600 - 308 ; 1:1000 ) because intrinsic yfp fluorescence levels were low in cultured neurons and tissue sections .
, with sample sizes ( n ) shown in figures or stated in text . statistical analyses were performed using sigmaplot 11 ( systat software ) .
normality tests ( shapiro - wilk ) and equal variance tests were run and passed ( p>0.05 ) before parametric statistical analyses were run .
 angelman syndrome is a severe neurodevelopmental disorder caused by deletion or mutation of the maternal allele of the ubiquitin protein ligase e3a ( ube3a)13 . in neurons , 
 the paternal allele of ube3a is intact but epigenetically silenced46 , raising the possibility that angelman syndrome could be treated by activating this silenced allele to restore functional ube3a protein7,8 . using an unbiased , high - content screen in primary cortical neurons from mice 
 , we identified 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 ube3a911 . 
 these results suggest 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 twelve weeks after cessation of topotecan treatment , suggesting transient topoisomerase inhibition can have enduring effects on gene expression . 
 while 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 . 
Methods Summary
Supplementary Material