Epigenetic regulation of the glucocorticoid receptor promoter 1(7) in adult rats.

Regulation of glucocorticoid receptor (GR) levels is an important stress adaptation mechanism. Transcription factor Nfgi-a and environmentally induced Gr promoter 1 7 methylation have been implicated in fine-tuning the expression of Gr 1 7 transcripts. Here, we investigated Gr promoter 1 7 methylation and Gr 1 7 expression in adult rats exposed to either acute or chronic stress paradigms. A strong negative correlation was observed between the sum of promoter-wide methylation levels and Gr 1 7 transcript levels, independent of the stressor. Methylation of individual sites did not, however, correlate with transcript levels. This suggested that promoter 1 7 was directly regulated by promoter-wide DNA methylation. Although acute stress increased Ngfi-a expression in the hypothalamic paraventricular nucleus (PVN), Gr 1 7 transcript levels remained unaffected despite low methylation levels. Acute stress had little effect on these low methylation levels, except at four hippocampal CpGs. Chronic stress altered the corticosterone response to an acute stressor. In the adrenal and pituitary glands, but not in the brain, this was accompanied by an increase in methylation levels in orchestrated clusters rather than individual CpGs. PVN methylation levels, unaffected by acute or chronic stress, were significantly more variable within- than between-groups, suggesting that they were instated probably during the perinatal period and represent a pre-established trait. Thus, in addition to the known perinatal programming, the Gr 1 7 promoter is epigenetically regulated by chronic stress in adulthood, and retains promoter-wide tissue-specific plasticity. Differences in methylation susceptibility between the PVN in the perinatal period and the peripheral HPA axis tissues in adulthood may represent an important "trait" vs. "state" regulation of the Gr gene.

The chromosome 15q14 locus for bipolar disorder and schizophrenia: is C15orf53 a major candidate gene?

Bipolar disorder (BD) and schizophrenia are complexly inherited and highly heritable disorders with currently unknown etiologies. Recently, two independent genome-wide association studies for BD identified a small region on chromosome 15q14-15.1, pointing to a locus close to the gene C15orf53. Previously, this genomic region was also found to co-segregate with periodic catatonia (SCZD10, OMIM %605419), an unsystematic schizophrenia according to Leonhard's classification, in several multiplex families, thus pointing to overlapping etiologies of both conditions. A susceptibility locus on chromosome 15q14-15.1 was narrowed down to a 4.38 Mb region in these affected families followed by mutation and segregation analyses of C15orf53. Association analysis of individuals affected by BD and/or SCZD10 (n = 274) and controls (n = 230) and expression analyses in distinct post-mortem human limbic brain tissues were conducted. C15orf53 revealed no mutations in our SCZD10 family members, but segregation of two common haplotypes was found. No association of identified haplotypes was found in our case-control samples. Gene expression could be demonstrated for immune-system-derived cells but not for the post-mortem human limbic brain tissue. Our results indicate that C15orf53 is probably neither causative for the etiology of BD nor for SCZD10 in our samples.