Endocrine Abstracts

The corticosteroids aldosterone and cortisol are implicated in the aetiology of hypertension. The CYP11B1 and CYP11B2 genes encode 11β-hydroxlylase and aldosterone synthase; polymorphisms across the CYP11B1/B2 locus are associated with increased aldosterone production, inefficient 11β-hydroxlation and hypertension. While polymorphisms located in the promoter region of both genes may alter transcription factor binding, other variants located in the introns and 3′-untranslated region (3′-UTR) may affect binding of regulatory microRNA (miRNA) species. MiRNAs are small, endogenous, non-coding RNAs, which originate from intronic or intergenic sequences. By binding to the 3′-UTR of mRNA they can cause post-transcriptional gene regulation. To determine the potential influence of miRNAs on regulation of CYP11B1 and CYP11B2, we measured miRNA expression in four non-tumourous human adrenals and used bioinformatic databases to predict miRNA binding sites in CYP11B1 and CYP11B2.

Methods: Total RNA was extracted from four human adrenal glands and miRNA expression measured using μParaflo technology microarray. Putative miRNA binding sites in CYP11B1 and CYP11B2 genes were screened using four miRNA bioinformatic databases (miRBASE, microRNA.org, TargetScan and miRanda).

Results: Microarray analysis identified 104 miRNAs expressed at a level greater than a predetermined signal intensity threshold. Bioinformatic analysis identified 198 putative miRNA binding sites in CYP11B1 and 154 in CYP11B2; 80 sites were common to both genes. By comparing microarray and bioinformatic data, we found 21 miRNAs that were present in adrenal glands with a predicted binding site in CYP11B1 and 18 miRNAs in CYP11B2; 13 miRNAs were common to both genes.

Conclusions: A miRNA expression profile for the human adrenal has been established for the first time. Microarray data combined with bioinformatic database analysis highlights numerous miRNAs that may be involved in regulation of CYP11B1 and CYP11B2. These data allow us to explore the hypothesis that dysregulation of miRNAs expression or binding may be important in adrenal pathophysiology.