Aldosterone and cortisol serve important roles in the pathogenesis of cardiovascular diseases and metabolic disorders. Epigenetics is a mechanism to control enzyme expression by genes without changing the gene sequence. Steroid hormone synthase gene expression is regulated by transcription factors specific to each gene, and methylation has been reported to be involved in steroid hormone production and disease. Angiotensin II or potassium regulates the aldosterone synthase gene, CYP11B2. The adrenocorticotropic hormone controls the 11b-hydroxylase, CYP11B1. DNA methylation negatively controls the CYP11B2 and CYP11B1 expression and dynamically changes the expression responsive to continuous stimulation of the promoter gene. Hypomethylation status of the CYP11B2 promoter region is seen in aldosterone-producing adenomas. Methylation of recognition sites of transcription factors, including cyclic AMP responsive element binding protein 1 or nerve growth factor-induced clone B, diminish their DNA-binding activity. A methyl-CpG-binding protein 2 cooperates directly with the methylated CpG dinucleotides of CYP11B2. A low-salt diet, treatment with angiotensin II, and potassium increase the CYP11B2 mRNA levels and induce DNA hypomethylation in the adrenal gland. A close association between a low DNA methylation ratio and an increased CYP11B1 expression is seen in Cushing’s adenoma and aldosterone-producing adenoma with autonomous cortisol secretion. Epigenetic control of CYP11B2 or CYP11B1 plays an important role in autonomic aldosterone or cortisol synthesis.

Angiotensinogen (AGT) and aldosterone play key roles in the regulation of blood pressure and are implicated in the pathogenesis of cardiovascular diseases. DNA methylation typically acts to repress gene transcription. The aldosterone synthase gene CYP11B2 is regulated by angiotensin II and potassium. DNA methylation negatively regulates AGT and CYP11B2 expression and dynamically changes in response to continuous promoter stimulation of each gene. High salt intake and excess circulating aldosterone cause DNA demethylation around the CCAAT-enhancer-binding-protein (CEBP) sites of the ATG promoter region, thereby converting the phenotype of AGT expression from an inactive to an active state in visceral adipose tissue and heart. A close association exists between low DNA methylation at CEBP-binding sites and increased AGT expression in salt-sensitive hypertensive rats. Salt-dependent hypertension may be partially affected by increased cardiac AGT expression. CpG dinucleotides in the CYP11B2 promoter are hypomethylated in aldosterone-producing adenomas. Methylation of recognition sequences of transcription factors, including CREB1, NGFIB (NR4A1), and NURR1 (NR4A2) diminish their DNA-binding activity. The methylated CpG-binding protein MECP2 interacts directly with the methylated CYP11B2 promoter. Low salt intake and angiotensin II infusion lead to upregulation of CYP11B2 expression and DNA hypomethylation in the adrenal gland. Treatment with the angiotensin II type 1 receptor antagonist decreases CYP11B2 expression and leads to DNA hypermethylation. A close association between low DNA methylation and increased CYP11B2 expression are seen in the hearts of patients with hypertrophic cardiomyopathy. These results indicate that epigenetic regulation of both AGT and CYP11B2 contribute to the pathogenesis of cardiovascular diseases.

Background: DNA methylation is believed to be maintained in adult somatic cells. Recent findings, however, suggest that all methylation patterns are not stable. We demonstrate that stimulatory signals can change the DNA methylation status around transcription factor binding sites and a transcription start site and activate expression of the aldosterone synthase gene ( CYP 11B2 ). Methods and Results: DNA methylation of CYP 11B2 was analyzed in aldosterone‐producing adenomas, nonfunctioning adrenal adenomas, and adrenal glands and compared with the gene expression levels. CpG dinucleotides in the CYP 11B2 promoter were found to be hypormethylated in tissues with high expression, but not in those with low expression, of CYP 11B2 . Methylation of the CYP 11B2 promoter fused to a reporter gene decreased transcriptional activity. Methylation of recognition sequences of transcription factors, including CREB 1, NGFIB ( NR 4A1), and NURR 1 ( NR 4A2) diminished their DNA ‐binding activity. A methylated‐CpG‐binding protein MECP 2 interacted directly with the methylated CYP 11B2 promoter. In rats, low salt intake led to upregulation of CYP 11B2 expression and DNA hypomethylation in the adrenal gland. Treatment with angiotensin II type 1 receptor antagonist decreased CYP 11B2 expression and led to DNA hypermethylation. Conclusions: DNA demethylation may switch the phenotype of CYP 11B2 expression from an inactive to an active state and regulate aldosterone biosynthesis.

Study of two families containing individuals with nephrogenic diabetes insipidus (NDI) indicated different types of 21.3 kb and 26.3 kb deletions involving the AVPR2 and ARHGAP4 (RhoGAP C1) genes. In the case of the 21.3 kb deletion, the deletion consensus motif (5′‐TGAAGG‐3′) and polypurine runs, known as the arrest site of polymerase alpha, were detected in the vicinity of the deletion junction. Inverted repeats (7/8 matches), believed to potentiate DNA loop formation, flank the deletion breakpoint. We propose this deletion to be the result of slipped mispairing during DNA replication. In the case of the 26.3 kb deletion, the 12,945 bp inverted region with the 10,003 bp internal deletion was accompanied with the 2,509 bp deletion in the 5′‐side and the 13,785 bp deletion in the 3′‐side. We defined three deletion junctions in this rearrangement (DJ1, DJ2, and DJ3) from the 5′‐side. The surrounding sequence of DJ1 (5′‐CCC‐3′) closely resembled that of DJ3 (5′‐AGGG‐3′) (DJ1; 5′‐cCCCgaggg‐3′, DJ3; 5′‐ccccAGGG‐3′), and DJ1 was located in the 5′‐side of DJ3 without any overlapping in sequence. The immunoglobulin class switch (ICS) motif (5′‐TGGGG‐3′) was found around the complementary sequence of DJ3. There was a 10‐base palindrome (5′‐aGACAtgtct‐3′) in the alignment of the DJ2 (5′‐GACA‐3′) region. From these findings, we propose a novel mutation process with the rearrangement probably resulting from stem‐loop induced non‐homologous recombination in an ICS‐like fashion. Both patients, despite lacking ARHGAP4, had no morphological, clinical, or laboratory abnormalities except for those usually found in patients with NDI. Hum Mutat 19:23–29, 2002.