ABSTRACT: Background: We have recently identified the nuclear hormone receptor RORA (retinoic acid-related orphan receptor-alpha) as a novel candidate gene for autism spectrum disorder (ASD). Our independent cohort studies have consistently demonstrated the reduction of RORA transcript and/or protein levels in blood-derived lymphoblasts as well as the postmortem prefrontal cortex and cerebellum of individuals with ASD. Moreover, we have also shown that RORA has the potential to be under negative and positive regulation by androgen and estrogen, respectively, suggesting the possibility that RORA may contribute to the male bias of ASD. However, little is known about transcriptional targets of this nuclear receptor, particularly in humans. Methods: Here we comprehensively identify transcriptional targets of RORA in human neuronal cells using chromatin immunoprecipitation (ChIP), followed by whole-genome promoter array (chip) analysis. Selected potential targets of RORA were then further validated by an independent chromatin immunoprecipitation, followed by qPCR analysis. To further demonstrate that reduced RORA expression results in aberrant transcription of RORA targets, we determined the expression levels of selected transcriptional targets in RORA-deficient human neuronal cells, as well as in postmortem brain tissues from individuals with ASD who exhibit reduced RORA expression. Results: The ChIP-on-chip analysis reveals that RORA1, a major isoform of RORA protein in human brain, can be recruited to as many as 1,338 genomic locations corresponding to promoter regions of 1,274 genes across the human genome. Among the genes potentially directly regulated by RORA1 are genes known to have biological functions negatively impacted in individuals with ASD, including neuronal adhesion and survival, synaptogenesis, and development of the cortex and the cerebellum. Independent ChIP-qPCR analyses confirm binding of RORA1 to promoter regions of several ASD-associated genes, including A2BP1, CYP19A1, HSD17B10, ITPR1, NLGN1, and NTRK2, whose expression levels are also decreased in RORA1-repressed human neuronal cells and in prefrontal cortex tissues from individuals with ASD. Conclusion: Findings from this study indicate that RORA transcriptionally regulates A2BP1, CYP19A1, HSD17B10, ITPR1, NLGN1, and NTRK2, and strongly suggest that reduction of this sex hormone-sensitive nuclear receptor in the brain causes dysregulated expression of these genes which, in turn, may contribute to the underlying pathobiology of ASD.
