Tet1-dependent epigenetic modification of BDNF expression in dorsal horn neurons mediates neuropathic pain in rats

Abstract

Ten-eleven translocation methylcytosine dioxygenase 1 (Tet1) mediates the conversion of 5-methylcytosine (5 mC) to 5-hydroxymethylcytosine (5 hmC), hence promoting DNA demethylation. Although recent studies have linked the DNA demethylation of specific genes to pain hypersensitivity, the role of spinal Tet1-dependent DNA demethylation in nociception hypersensitivity development remains elusive. Here, we report correlated with behavioral allodynia, spinal nerve ligation (SNL) upregulated Tet1 expression in dorsal horn neurons that hydroxylate 5 mC to 5 hmC at CpG dinucleotides in the bdnf promoter to promote spinal BDNF expression at day 7 after operation. Focal knockdown of spinal Tet1 expression decreased Tet1 binding and 5 hmC enrichment, further increased 5 mC enrichment at CpG sites in the bdnf promoter and decreased spinal BDNF expression accompanied by the alleviation of the developed allodynia. Moreover, at day 7 after operation, SNL-enhanced Tet1 expression also inhibited the binding of DNA methyltransferases (DNMTs, i.e., DNMT1, DNMT3a, and DNMT3b) to the bdnf promoter, a requirement for transcriptional silencing by catalysing 5-cytosine (5C) to 5 mC. Together, these data suggest at CpG sites of the bdnf promoter, SNL-enhanced Tet1 expression promotes DNA demethylation both by converting 5 mC to 5 hmC and inhibiting DNMT binding to regulate spinal BDNF expression, hence contributing to behavioral allodynia development.

TET1 Overexpression Mitigates Neuropathic Pain Through Rescuing the Expression of μ-Opioid Receptor and Kv1.2 in the Primary Sensory Neurons

“…Recent work suggests the involvement of TET1 in pathological pain. TET1 is expressed exclusively in the neurons of the DRG and spinal cord dorsal horn [34,35], 2 major pain-related regions in the nervous system. Peripheral SNL and paw injection of formalin or complete Freund's adjuvant (CFA) increased TET1 expression in ipsilateral spinal cord dorsal horn, but not in the DRG [14,[34][35][36][37][38].…”

“…TET1 is expressed exclusively in the neurons of the DRG and spinal cord dorsal horn [34,35], 2 major pain-related regions in the nervous system. Peripheral SNL and paw injection of formalin or complete Freund's adjuvant (CFA) increased TET1 expression in ipsilateral spinal cord dorsal horn, but not in the DRG [14,[34][35][36][37][38]. Knockdown of spinal TET1 alleviated the formalin-, CFA-, and SNL-induced nociceptive behaviors through blocking TET1-triggered expression of dorsal horn miR-365, Stat3, and BDNF, respectively [35,37,38].…”

“…Peripheral SNL and paw injection of formalin or complete Freund's adjuvant (CFA) increased TET1 expression in ipsilateral spinal cord dorsal horn, but not in the DRG [14,[34][35][36][37][38]. Knockdown of spinal TET1 alleviated the formalin-, CFA-, and SNL-induced nociceptive behaviors through blocking TET1-triggered expression of dorsal horn miR-365, Stat3, and BDNF, respectively [35,37,38]. Overexpression of TET1 in the spinal cord led to pain-like behaviors [35,37,38].…”

FAM20C could be targeted by TET1 to promote odontoblastic differentiation potential of human dental pulp cells

“…Louisa et al reported that TET1 directly binds to the promoter of insulin‐like growth factor 2 mRNA binding protein 1 (IGF2BP1) and influences the DNA hydroxymethylation status of its promoter, which can contribute to the stemness of human mesenchymal stem cells. Knocking down the rat spinal TET1 decreased 5hmC enrichment and further increased 5mC enrichment on the promoter CpG sites of the brain‐derived neurotrophic factor gene, attenuating its expression . Given that the expression pattern of FAM20C and the effect of FAM20C depletion on the odontoblastic differentiation of hDPCs were quite similar to those of TET1 and that FAM20C with a putative long CGI in its promoter is thought to be one of the potential TET1‐occupancy genes in Mus musculus, we were prompted to explore the possibility that TET1 might regulate FAM20C transcription through its hydroxymethylation status in hDPCs.…”

“…Knocking down the rat spinal TET1 decreased 5hmC enrichment and further increased 5mC enrichment on the promoter CpG sites of the brain-derived neurotrophic factor gene, attenuating its expression. 45 Given that the expression pattern of FAM20C and the effect of FAM20C depletion on the odontoblastic differentiation of hDPCs were quite similar to those of TET1 and that FAM20C with a putative long CGI in its promoter is thought to be one of the potential TET1-occupancy genes in Mus musculus, we were prompted to explore the possibility that TET1 might regulate FAM20C transcription through its hydroxymethylation status in hDPCs. Our results revealed that TET1 deficiency with no compensatory upregulation of TET2 or TET3 led to significantly reduced odontoblast marker expression and a concomitant reduction in FAM20C levels.…”