Promoter haplotypes of the corticotropin-releasing hormone encoding gene modulate the physiological stress response in vitro and in vivo.

The corticotropin-releasing hormone (CRH) is a neuropeptide mediating stress responses. CRH exerts effects via the hypothalamus pituitary adrenal axis as well as immediate effects on the sympathetic-adrenal-medullary system. Genetic variants of the CRH promoter were previously found to be associated with altered CRH promoter activity and physiological reactions. Functional characterization of three CRH promoter haplotypes have been performed in vitro using a reporter gene assay under different stimulation conditions. Furthermore, 232 healthy subjects were genotyped and the influence of CRH haplotypes on basal parameters such as post-awakening cortisol and blood pressure as well as on stress reactivity measured after socially evaluated cold pressor test (SeCPT) was investigated. In vitro, CRH haplotype 2 showed the highest promoter activity under baseline conditions and after forskolin stimulation compared with other haplotypes. Forskolin treatment resulted in a two fold increase of haplotype 2 promoter activity compared with the baseline condition. Cell line-dependent promoter activation was found after hydrocortisone treatment. In vivo, CRH haplotype 2 carriers showed significant higher baseline blood pressure (p = .002) and blood pressure after SeCPT (p < .001), but did not differ in cortisol levels. This study provides converging evidence for the importance of CRH promoter variants on physiological stress response parameters.

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.

A new transcript splice variant of the human glucocorticoid receptor: identification and tissue distribution of hGR Delta 313-338, an alternative exon 2 transactivation domain isoform.

All human glucocorticoid receptor (hGR) isoforms are encoded by the NR3C1 gene consisting of seven core exons (exons 2-8) common to all protein isoforms. The gene has two major exon 8-9 splice variants and a 5'-UTR consisting of 11 alternative splice variants. The N-terminal region of the hGR includes a tau 1 transactivation domain that interacts with proteins in the basal transcriptional apparatus, including the TATA box-binding protein. Here, we report the existence and the tissue distribution of a novel splice variant, hGRDelta313-338, with a 26 residue (78 bp) deletion in this N-terminal region encoded by exon 2, between amino acids 313 and 338. The hGRDelta313-338 observed at the mRNA level represents a transcript variant encoding a smaller protein isoform detected by WB with a predicted deletion between the tau 1 domain and the DNA-binding domain (DBD) encoded by exons 3 and 4. Previous studies in transgenic mice showed that the removal of the entire exon 2 covering both the tau 1 transactivation domain and our deleted region produced a functional receptor albeit with an altered glucocorticoid-induced gene transcription pattern. Interestingly, the deleted residues show a number of potential phosphorylation sites including serine 317, known to be phosphorylated. It is thought that phosphorylation plays an important role in transactivation action of hGR. Thus, we hypothesize that hGRDelta313-338 represents a hGR isoform with an altered glucocorticoid-induced transactivation profile.