Elsevier

Neuroscience

Volume 166, Issue 1, 10 March 2010, Pages 1-4
Neuroscience

Rapid Report
Neuron-restrictive silencer factor causes epigenetic silencing of Kv4.3 gene after peripheral nerve injury

https://doi.org/10.1016/j.neuroscience.2009.12.021Get rights and content

Abstract

Peripheral nerve injury causes a variety of alterations in pain-related gene expression in primary afferent, which underlie the neuronal plasticity in neuropathic pain. One of the characteristic alterations is a long-lasting downregulation of voltage-gated potassium (Kv) channel, including Kv4.3, in the dorsal root ganglion (DRG). The present study showed that nerve injury reduces the messenger RNA (mRNA) expression level of Kv4.3 gene, which contains a conserved neuron-restrictive silencer element (NRSE), a binding site for neuron-restrictive silencer factor (NRSF). Moreover, we found that injury causes an increase in direct NRSF binding to Kv4.3-NRSE in the DRG, using chromatin immunoprecipitation (ChIP) assay. ChIP assay further revealed that acetylation of histone H4, but not H3, at Kv4.3-NRSE is markedly reduced at day 7 post-injury. Finally, the injury-induced Kv4.3 downregulation was significantly blocked by antisense-knockdown of NRSF. Taken together, these data suggest that nerve injury causes an epigenetic silencing of Kv4.3 gene mediated through transcriptional suppressor NRSF in the DRG.

Section snippets

Animals and surgery

Male C57BL/6J mice weighing 20–25 g were used. They were kept in a room with a temperature of 21±2 °C with free access to standard laboratory diet and tap water. The experiments were designed to minimize the number of animals used and their suffering. All procedures were approved by the Nagasaki University Animal Care Committee and were carried out in accordance with the National Institute of Health Guide for the Care and Use of Laboratory Animals. Partial sciatic nerve ligation was performed

Results

To examine whether Kv4.3 is downregulated at the transcriptional level after injury, we quantified its mRNA expressions in the DRG by real-time PCR. There was a significant reduction in Kv4.3 expression starting from day 7 post-injury, which persisted at least 14 days (Fig. 1A). Using TFSEARCH program (version 1.3, available at: http://www.cbrc.jp/research/db/TFSEARCHJ.html), we found that mouse Kv4.3 gene contains a putative NRSE sequence within intron 2, which is completely conserved in rat (

Discussion

Given that the long-term changes in pain-related gene expression underlie the most important mechanisms responsible for injury-induced neuropathic pain (Hökfelt et al., 2006, Ueda, 2006), we focused on the critical contribution of epigenetic mechanisms (Borrelli et al., 2008). Here, we demonstrated that injury-induced Kv4.3 downregulation, which is implicated in neuronal hyperexcitability underlying neuropathic pain (Kim et al., 2002, Chien et al., 2007), is closely related to the

Conclusion

In conclusion, the present study demonstrated that NRSF plays a key role in injury-induced Kv4.3 downregulation in the DRG through epigenetic mechanisms. A study concerning the regulatory mechanisms for NRSE-NRSF system after injury is the next subject for research.

Acknowledgments

We thank W. Xie for technical help. This work was supported by MEXT KAKENHI (17109015 to Hiroshi Ueda). Health Sciences Research Grants from the Ministry of Health, Labor and Welfare of Japan (Hiroshi Ueda) and Health Labour Sciences Research Grant “Third Term Comprehensive Control Research for Cancer” (398-49) are also supported this work.

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These authors have contributed equally to this manuscript.

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