DNA羟化酶TET1抑制甲状腺功能的机制研究

正常的甲状腺激素（TH）水平是维持机体基础代谢、多器官发育及生理功能的关键。甲状腺功能异常是不容忽视的内分泌疾病，可累积全身多个系统，近年来发病率急剧增加，严重影响人们的身心健康。TH合成及分泌主要依赖甲状腺刺激激素受体（TSHR）及下游转录因子的调控，而表观遗传学调控机制目前尚无报道。DNA羟化酶TET1介导DNA主动去甲基化及染色质重塑，参与基因表达调控。我们的前期研究发现在甲状腺中引入BrafV600E突变可导致小鼠发生严重的甲状腺功能减退，使之丧失生殖能力，而联合敲除Tet1基因可有效恢复小鼠的甲状腺功能及其生育能力，提示TET1可能负向调控甲状腺功能。本项目旨在此基础上拟通过RNA-Seq、ChIP-Seq、细胞生物能量分析等技术手段筛选TET1的下游靶基因，阐明其抑制甲状腺功能的分子机制，从表观遗传学视角完善TH合成及分泌的调控机制，为甲状腺功能异常提供新的治疗策略和思路。

Thyroid hormone (TH) plays a critical role in maintaining basal metabolic rate and the development of target organs, including central nervous system, skeletal and reproductive systems. Any abnormality in the intricate system of thyroid gland and hormone synthesis can introduce thyroid dysfunction and bring systematic damages even irreversible disabilities. Thyroid function is generally regulated by thyrotropin receptor (TSHR) and its downstream transcritpion factors including TTF1/2, PAX8, and CREB. However, the importance of epigenetic mechanisms in these key processes remains largely unknown. TET1 is a DNA hydroxylase that convert 5-methycytosine (5-mC) into 5-hydroxylmethylcytosine (5-hmC), and is involved in regulating gene expression through DNA demethylation and chromatin remodeling. Our preliminary data showed that severe hypothyroidism was observed in the thyroid glands of transgenic mice with thyroid-specific knock-in of BrafV600E (TPO-Cre/LSL-BrafV600E), resulting in loss of body weight and fertility in mice. Interestingly, we found that mice restored thyroid function and reproductive ability when Tet1 was knocked-out specifically in the thyroid gland of TPO-Cre/LSL-BrafV600E mice. These data suggest that TET1 negatively regulates thyroid function. The aims of this project were to identify the target genes of TET1 and explore the mechanism underlying the inhibitory effect of TET1 on thyroid function by using RNA-Seq, ChIP-Seq and cell bioenergy analysis. This study will help us to better understand the role of epigenetic mechanisms in regulating thyroid function and provide therapeutic startegies for thyroid dysfunction.