Molecular Basis for Glucocorticoid Induction of the Krüppel-Like Factor 9 Gene in Hippocampal Neurons

Abstract

Stress has complex effects on hippocampal structure and function, which consequently affects learning and memory. These effects are mediated in part by circulating glucocorticoids (GC) acting via the intracellular GC receptor (GR) and mineralocorticoid receptor (MR). Here, we investigated GC regulation of Krüppel-like factor 9 (KLF9), a transcription factor implicated in neuronal development and plasticity. Injection of corticosterone (CORT) in postnatal d 6 and 30 mice increased Klf9 mRNA and heteronuclear RNA by 1 h in the hippocampal region. Treatment of the mouse hippocampal cell line HT-22 with CORT caused a time- and dose-dependent increase in Klf9 mRNA. The CORT induction of Klf9 was resistant to protein synthesis inhibition, suggesting that Klf9 is a direct CORT-response gene. In support of this hypothesis, we identified two GR/MR response elements (GRE/MRE) located -6.1 and -5.3 kb relative to the transcription start site, and we verified their functionality by enhancer-reporter, gel shift, and chromatin immunoprecipitation assays. The -5.3-kb GRE/MRE is largely conserved across tetrapods, but conserved orthologs of the -6.1-kb GRE/MRE were only detected in therian mammals. GC treatment caused recruitment of the GR, histone hyperacetylation, and nucleosome removal at Klf9 upstream regions. Our findings support a predominant role for GR, with a minor contribution of MR, in the direct regulation of Klf9 acting via two GRE/MRE located in the 5'-flanking region of the gene. KLF9 may play a key role in GC actions on hippocampal development and plasticity.

Krüppel-like Factor 13 Is a Major Mediator of Glucocorticoid Receptor Signaling in Cardiomyocytes and Protects These Cells from DNA Damage and Death

“…2 and 3). These findings are supported by studies that have demonstrated that glucocorticoid receptor directly regulates several members of the KLF family (41,42). We also found that KLF13 is a direct target of GR and its regulation involves binding of activated glucocorticoid receptors to a conserved and functional GRE within intron 1 of the Klf13 gene (Figs.…”

Krüppel-like factors in mammalian stem cells and development

“…As mentioned earlier, KLF9 is implicated in neuronal development, and recent studies have also determined that KLF9 regulates neuronal plasticity by mediating the stress-induced effects of glucocorticoids in hippocampal neurons (Bagamasbad et al, 2012;Bonett et al, 2009). In addition, thyroid hormone induced oligodendrocyte differentiation and myelin regeneration are regulated by KLF9, which has direct implications in demyelinating disorders such as multiple sclerosis (Dugas et al, 2012).…”

Stress-induced gene expression and behavior are controlled by DNA methylation and methyl donor availability in the dentate gyrus

“…For instance, in silico analysis of transcription factor binding sites presented specificity protein 1 (Sp1) and Krüppel-like factor 9 (Klf9) sites within the DNA sequence of area A. The Klf9 gene contains glucocorticoid response elements (GREs), and expression is induced in response to elevated corticosterone levels (29), which are known to occur after FS (30). Thus, the SAM and FS-induced increases in CpG methylation in this region of the Egr-1 gene may have disrupted Klf9-mediated (and possibly Sp1-mediated) transcriptional activation, but confirmation of this postulate requires further investigation.…”