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Stress exacerbates disease, and understanding its molecular mechanisms is crucial to the development of novel therapeutic interventions to combat stress-related disorders. The driver of the stress response in the hypothalamic-pituitary-adrenal axis (HPA) is corticotropin-releasing hormone (CRH), a neuropeptide synthesized in the paraventricular nucleus of the hypothalamus. Evidence supports that CRH expression is epigenetically modified at the molecular level by environmental stimuli, causing changes in the stress response. This effect is mediated by a concert of factors that translate environmental change into alterations in gene expression. An important regulator and epigenetic modulator of CRH expression is neuron-restrictive silencing factor (NRSF). Previously, our lab identified numerous splice variants of NRSF that are specific to humans and predictive of differential regulatory effects of NRSF variants on targeted gene expression. The human cell line BeWo has endogenous CRH and NRSF expression providing an in vitro model system. Here, we show that manipulation of NRSF expression through siRNA technology, overexpression by plasmid vectors, and direct cAMP induction that CRH expression is linked to changes in NRSF expression. Accordingly, this epigenetic regulatory pathway in humans might be a critical mechanism involved in the regulation of the stress response.

Huntington's disease (HD) is caused by a genetically mutated huntingtin (mHtt) protein with expanded polyQ stretch, which impairs cytosolic sequestration of the repressor element‐1 silencing transcription factor (REST), resulting in excessive nuclear REST and subsequent repression of neuronal genes. We recently demonstrated that REST undergoes extensive, context‐dependent alternative splicing, of which exon‐3 skipping (∆E3)—a common event in human and nonhuman primates—causes loss of a motif critical for REST nuclear targeting. This study aimed to determine whether ∆E3 can be targeted to reduce nuclear REST and rescue neuronal gene expression in mouse striatal‐derived, mHtt‐expressing STHdhQ111/Q111 cells—a well‐established cellular model of HD. We designed two morpholino antisense oligos (ASOs) targeting the splice sites of Rest E3 and examined their effects on ∆E3, nuclear Rest accumulation and Rest‐controlled gene expression in STHdhQ111/Q111 cells. We found that (1) the ASOs treatment significantly induced ∆E3, reduced nuclear Rest, and rescued transcription and/or mis‐splicing of specific neuronal genes (e.g. Syn1 and Stmn2) in STHdhQ111/Q111 cells; and (2) the ASOs‐induced transcriptional regulation was dependent on ∆E3 induction and mimicked by siRNA‐mediated knock‐down of Rest expression. Our findings demonstrate modulation of nuclear REST by ∆E3 and its potential as a new therapeutic target for HD and provide new insights into environmental regulation of genome function and pathogenesis of HD. As ∆E3 is modulated by cellular signalling and linked to various types of cancer, we anticipate that ∆E3 contributes to environmentally tuned REST function and may have a broad range of clinical implications.

As a major orchestrator of the cellular epigenome, the repressor element-1 silencing transcription factor (REST) can either repress or activate thousands of genes depending on cellular context, suggesting a highly context-dependent REST function tuned by environmental cues. While REST shows cell-type non-selective active transcription (Kojima et al., 2001), an N-terminal REST4 isoform caused by alternative splicing, inclusion of an extra exon (N3c) which introduces a pre-mature stop codon, contributes to neurogenesis and tumorigenesis (Palm et al., 1998, 1999; Lee et al., 2000; Raj et al., 2011). Recently, in line with established epigenetic regulation of pre-mRNA splicing (Allo et al., 2010; Luco et al., 2011), we demonstrated that REST undergoes extensive, context-dependent alternative splicing which results in the formation of a large number of mRNA variants predictive of multiple protein isoforms (Chen and Miller, 2013). Supported by the fact that immunoblotting/-staining with different anti-REST antibodies yield different results, alternative splicing allows production of various structurally and functionally different REST protein isoforms in response to shifting physiologic requirements, shedding light on environmental regulation of REST function. However, REST isoforms might be differentially assayed or manipulated, leading to data misinterpretation and controversial findings. For example, in contrast to the proposed neurotoxicity of elevated nuclear REST in ischemia (Noh et al., 2012) and Huntington’s disease (Zuccato et al., 2003; Buckley et al., 2010), Lu et al. recently reported decreased nuclear REST in Alzheimer’s disease and neuroprotection of REST in aging brain (Lu et al., 2014). Unfortunately, alternative REST splicing was largely neglected by Lu et al. (2014), making it necessary for a reevaluation of their findings. As shown in Figure 1 A , human REST gene boundary is now doubled by an alternative …