Distribution Of5-hydroxymethylcytosine(5hmC)in Rat Brain Tissues And The Role Of5hmC In Brain Development

Background:5-hydroxymethylcytosine (5hmC) has recently been discovered as a new epigenetic modified base in higher organisms, but the concrete function of5hmC remains elusive. Hydroxylation of5mC by the TET proteins could yield5hmC. Previous study showed that5hmC was widely distributed in mice and human brain tissues. And5hmC levels in hippocampus and cerebellum had increased with aging. Besides,5hmC was also a form of oxidatively damaged nucleobases. Based on these theories, we hypothesized that5hmC might also exist in rat brain tissues. Moreover, if we confirmed that5hmC existed in rat striatum, it should be very interesting to explore whether striatal DNA5hmC levels changed during the aging and development process.6-OHDA induced rat was a classical vivo model of PD and numerous evidences were linked to the oxidative stress in6-OHDA induced rat. Thus we used this PD model to investigate whether striatal DNA5hmC would be formed under the oxidative stress in vivo study.Methods:A rat model of aging was used, including postnatal day1(P1) male Sprague-Dawley (SD) rats, P21male SD rats and P65male SD rats. Each group has6rats and bilateral striatum has been used.6-OHDA induced rat was used as the classical vivo PD model. Each group has6rats and the right striatum has been used. Brain tissues including bilateral striatum, bilateral cerebral cortex, bilateral hippocampus, bilateral brainstem and bilateral cerebellum were obtained from SD rats. Each group has6rats. Global DNA was obtained from these tissues. The global5hmC DNA content was measured with the corresponding ELISA.Results:The data showed that the global5hmC DNA content was widely distributed in the investigated rat brain tissues and it was tissue-specific. Difference of global striatal5hmC was found in P21rat compared to P1rat (P<0.05). Difference of global striatal5hmC was also found in P65rat compared to P21rat (P<0.05).We also found that global striatal5hmC content increased from P1to adult rat. But no difference of global striatal5hmC was found in6-OHDA induced rat compared to the normal rat (P>0.05).Conclusion:These findings indicated that we revealed the first global5hmC DNA content distribution in the rat brain. Particularly, we revealed for the first time that global5hmC DNA content exists in striatum. Moreover, we demonstrated that5hmC might play a critical role in striatum maturation. Finally, in the6-OHDA induced rat (vivo PD model),5hmC might not change.