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Expression of DNA methyltransferases in adult dorsal root ganglia is cell-type specific and up regulated in a rodent model of neuropathic pain.

Pollema-Mays SL, Centeno MV, Apkarian AV, Martina M - Front Cell Neurosci (2014)

Bottom Line: Real-time RT PCR analysis revealed robust and time-dependent changes in DNMT transcript expression in ipsilateral DRGs from spared nerve injury (SNI) but not sham rats.Interestingly, DNMT3b transcript showed a robust upregulation that appeared already 1 week after surgery and persisted at 4 weeks (our endpoint); in contrast, DNMT1 and DNMT3a transcripts showed only moderate upregulation that was transient and did not appear until the second week.We suggest that DNMT regulation in adult DRGs may be a contributor to the pain phenotype and merits further study.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, Northwestern University Feinberg School of Medicine Chicago, IL, USA.

ABSTRACT
Neuropathic pain is associated with hyperexcitability and intrinsic firing of dorsal root ganglia (DRG) neurons. These phenotypical changes can be long lasting, potentially spanning the entire life of animal models, and depend on altered expression of numerous proteins, including many ion channels. Yet, how DRGs maintain long-term changes in protein expression in neuropathic conditions remains unclear. DNA methylation is a well-known mechanism of epigenetic control of gene expression and is achieved by the action of three enzymes: DNA methyltransferase (DNMT) 1, 3a, and 3b, which have been studied primarily during development. We first performed immunohistochemical analysis to assess whether these enzymes are expressed in adult rat DRGs (L4-5) and found that DNMT1 is expressed in both glia and neurons, DNMT3a is preferentially expressed in glia and DNMT3b is preferentially expressed in neurons. A rat model of neuropathic pain was then used to determine whether nerve injury may induce epigenetic changes in DRGs at multiple time points after pain onset. Real-time RT PCR analysis revealed robust and time-dependent changes in DNMT transcript expression in ipsilateral DRGs from spared nerve injury (SNI) but not sham rats. Interestingly, DNMT3b transcript showed a robust upregulation that appeared already 1 week after surgery and persisted at 4 weeks (our endpoint); in contrast, DNMT1 and DNMT3a transcripts showed only moderate upregulation that was transient and did not appear until the second week. We suggest that DNMT regulation in adult DRGs may be a contributor to the pain phenotype and merits further study.

No MeSH data available.


Related in: MedlinePlus

DNMT3b transcript expression remains exclusively neuronal after peripheral nerve injury. Immunohistochemisry was performed on sections obtained from DRG ipsilateral to the peripheral injury in two SNI rats 1 week post-surgery. (A,B) are two examples of images obtained by staining the DRG sections with DNMT3b (green) antibody and DAPI (blue). Note that, similar to the naïve tissue, DNMT3b expression is ubiquitous in neurons, but absent from glia.
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Figure 5: DNMT3b transcript expression remains exclusively neuronal after peripheral nerve injury. Immunohistochemisry was performed on sections obtained from DRG ipsilateral to the peripheral injury in two SNI rats 1 week post-surgery. (A,B) are two examples of images obtained by staining the DRG sections with DNMT3b (green) antibody and DAPI (blue). Note that, similar to the naïve tissue, DNMT3b expression is ubiquitous in neurons, but absent from glia.

Mentions: At 4 weeks post injury, in the ipsilateral DRG both DNMT1 and DNMT3a transcripts still showed a trend for a slight increase relative to sham controls (28% for DNMT1, p = 0.09, 42% for DNMT3a, p = 0.22); no significant increase was found in the DRG contralateral to nerve injury (Figure 4C). DNMT3b transcript was still significantly elevated by 41% in the DRG ipsilateral to nerve injury (p < 0.05). DRGs contralateral to injury showed no changes. Thus, these data demonstrate that nerve injury associated changes in DNMT3b expression are early and robust, while changes in DNMT1 and DNMT3a occur later and more transiently. Thus, only DNMT3b transcript expression was significantly increased at all time points after surgery. Because, in control conditions, this transcript is found in all neurons, but not in glia, we wanted to verify whether this qualitative pattern is maintained after peripheral nerve injury. Therefore, immunohistochemistry was performed on DRG sections from 2 SNI animals 1 week after the surgery, when the transcript expression was the highest (Figure 5). We found that, similar to the naïve rat condition, DNMT3b expression was still neuronal-specific and no evidence for glial expression was found.


Expression of DNA methyltransferases in adult dorsal root ganglia is cell-type specific and up regulated in a rodent model of neuropathic pain.

Pollema-Mays SL, Centeno MV, Apkarian AV, Martina M - Front Cell Neurosci (2014)

DNMT3b transcript expression remains exclusively neuronal after peripheral nerve injury. Immunohistochemisry was performed on sections obtained from DRG ipsilateral to the peripheral injury in two SNI rats 1 week post-surgery. (A,B) are two examples of images obtained by staining the DRG sections with DNMT3b (green) antibody and DAPI (blue). Note that, similar to the naïve tissue, DNMT3b expression is ubiquitous in neurons, but absent from glia.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126486&req=5

Figure 5: DNMT3b transcript expression remains exclusively neuronal after peripheral nerve injury. Immunohistochemisry was performed on sections obtained from DRG ipsilateral to the peripheral injury in two SNI rats 1 week post-surgery. (A,B) are two examples of images obtained by staining the DRG sections with DNMT3b (green) antibody and DAPI (blue). Note that, similar to the naïve tissue, DNMT3b expression is ubiquitous in neurons, but absent from glia.
Mentions: At 4 weeks post injury, in the ipsilateral DRG both DNMT1 and DNMT3a transcripts still showed a trend for a slight increase relative to sham controls (28% for DNMT1, p = 0.09, 42% for DNMT3a, p = 0.22); no significant increase was found in the DRG contralateral to nerve injury (Figure 4C). DNMT3b transcript was still significantly elevated by 41% in the DRG ipsilateral to nerve injury (p < 0.05). DRGs contralateral to injury showed no changes. Thus, these data demonstrate that nerve injury associated changes in DNMT3b expression are early and robust, while changes in DNMT1 and DNMT3a occur later and more transiently. Thus, only DNMT3b transcript expression was significantly increased at all time points after surgery. Because, in control conditions, this transcript is found in all neurons, but not in glia, we wanted to verify whether this qualitative pattern is maintained after peripheral nerve injury. Therefore, immunohistochemistry was performed on DRG sections from 2 SNI animals 1 week after the surgery, when the transcript expression was the highest (Figure 5). We found that, similar to the naïve rat condition, DNMT3b expression was still neuronal-specific and no evidence for glial expression was found.

Bottom Line: Real-time RT PCR analysis revealed robust and time-dependent changes in DNMT transcript expression in ipsilateral DRGs from spared nerve injury (SNI) but not sham rats.Interestingly, DNMT3b transcript showed a robust upregulation that appeared already 1 week after surgery and persisted at 4 weeks (our endpoint); in contrast, DNMT1 and DNMT3a transcripts showed only moderate upregulation that was transient and did not appear until the second week.We suggest that DNMT regulation in adult DRGs may be a contributor to the pain phenotype and merits further study.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, Northwestern University Feinberg School of Medicine Chicago, IL, USA.

ABSTRACT
Neuropathic pain is associated with hyperexcitability and intrinsic firing of dorsal root ganglia (DRG) neurons. These phenotypical changes can be long lasting, potentially spanning the entire life of animal models, and depend on altered expression of numerous proteins, including many ion channels. Yet, how DRGs maintain long-term changes in protein expression in neuropathic conditions remains unclear. DNA methylation is a well-known mechanism of epigenetic control of gene expression and is achieved by the action of three enzymes: DNA methyltransferase (DNMT) 1, 3a, and 3b, which have been studied primarily during development. We first performed immunohistochemical analysis to assess whether these enzymes are expressed in adult rat DRGs (L4-5) and found that DNMT1 is expressed in both glia and neurons, DNMT3a is preferentially expressed in glia and DNMT3b is preferentially expressed in neurons. A rat model of neuropathic pain was then used to determine whether nerve injury may induce epigenetic changes in DRGs at multiple time points after pain onset. Real-time RT PCR analysis revealed robust and time-dependent changes in DNMT transcript expression in ipsilateral DRGs from spared nerve injury (SNI) but not sham rats. Interestingly, DNMT3b transcript showed a robust upregulation that appeared already 1 week after surgery and persisted at 4 weeks (our endpoint); in contrast, DNMT1 and DNMT3a transcripts showed only moderate upregulation that was transient and did not appear until the second week. We suggest that DNMT regulation in adult DRGs may be a contributor to the pain phenotype and merits further study.

No MeSH data available.


Related in: MedlinePlus