These levels were slightly lower than expected from maternally expressed genes with an average of three maternal alleles, but this may reflect the complex transcriptional and posttranslational regulation of UBE3A. The function of UBE3A as a transcriptional coactivator has been largely unexplored in the context of human genetic disease, but, in a Drosophila model of 15q duplication syndrome, elevated levels of an enzymatically defective version of Dube3a were able to induce transcription of the dopamine regulator GTP cyclohydrolase I and elevate dopamine levels in the fly brain [46]. Here, UBE3A is linked to hereditary disease.