Martinez Maria Elena, Hernandez Arturo
Center for Molecular Medicine, Maine Medical Center Research Institute, MaineHealth, Scarborough, ME, United States.
Graduate School for Biomedical Science and Engineering, University of Maine, Orono, ME, United States.
Front Neurosci. 2021 Jun 29;15:703730. doi: 10.3389/fnins.2021.703730. eCollection 2021.
Thyroid hormones (TH) are critical for the development and function of the central nervous system (CNS). Although their effects on the rodent brain peak within 2-3 weeks postnatally, the fetal brain has been found largely insensitive to exogenously administrated TH. To address this issue, here we examined gene expression in brains from mouse fetuses deficient in the type 3 deiodinase (DIO3), the selenoenzyme responsible for clearing TH. At embryonic day E18.5 qPCR determinations indicated a marked increase in the mRNA expression of T3-responsive genes and . The increased expression of these genes was confirmed by hydridization in multiple areas of the cortex and in the striatum. RNA sequencing revealed 246 genes differentially expressed (70% up-regulated) in the brain of E18.5 -/- male fetuses. Differential expression of 13 of these genes was confirmed in an extended set of samples that included females. Pathway analyses of differentially expressed genes indicated enrichment in glycolysis and signaling related to axonal guidance, synaptogenesis and hypoxia inducible factor alpha. Additional RNA sequencing identified 588 genes differentially expressed (35% up-regulated) in the brain of E13.5 -/- male fetuses. Differential expression of 13 of these genes, including , and , was confirmed in an extended set of samples including females. Although pathway analyses of differentially expressed genes at E13.5 also revealed significant enrichment in axonal guidance and synaptogenesis signaling, top enrichment was found for functions related to the cell cycle, aryl hydrocarbon receptor signaling, PCP and kinetochore metaphase signaling pathways and mitotic roles of polo-like kinase. Differential expression at E13.5 was confirmed by qPCR for additional genes related to collagen and extracellular matrix and for selected transcription factors. Overall, our results demonstrate that the rodent fetal brain is sensitive to TH as early as E13.5 of gestational age, and suggest that TH distinctly affects brain developmental programs in early and late gestation. We conclude that DIO3 function is critical to ensure an adequate timing for TH action in the developing brain and is probably the main factor underlying the lack of effects on the fetal brain observed in previous studies after TH administration.
甲状腺激素（TH）对中枢神经系统（CNS）的发育和功能至关重要。尽管它们对啮齿动物大脑的影响在出生后2 - 3周内达到峰值，但已发现胎儿大脑对外源性给予的TH基本不敏感。为了解决这个问题，我们在此研究了3型脱碘酶（DIO3）缺陷的小鼠胎儿大脑中的基因表达，DIO3是负责清除TH的硒酶。在胚胎第18.5天，定量PCR测定表明T3反应性基因 和 的mRNA表达显著增加。这些基因表达的增加通过在皮质和纹状体的多个区域进行杂交得到证实。RNA测序显示在E18.5 -/-雄性胎儿的大脑中有246个基因差异表达（70%上调）。在包括雌性的扩展样本集中证实了其中13个基因的差异表达。对差异表达基因的通路分析表明在糖酵解以及与轴突导向、突触形成和缺氧诱导因子α相关的信号传导中富集。额外的RNA测序确定在E13.5 -/-雄性胎儿的大脑中有588个基因差异表达（35%上调）。在包括雌性的扩展样本集中证实了其中13个基因的差异表达，包括 、 和 。尽管对E13.5差异表达基因的通路分析也显示在轴突导向和突触形成信号传导中显著富集，但发现与细胞周期、芳烃受体信号传导、平面细胞极性（PCP）和动粒中期信号通路以及polo样激酶的有丝分裂作用相关的功能富集程度最高。通过定量PCR证实了E13.5时与胶原蛋白和细胞外基质相关的其他基因以及选定转录因子的差异表达。总体而言，我们的结果表明啮齿动物胎儿大脑早在胎龄E13.5时就对TH敏感，并表明TH在妊娠早期和晚期对大脑发育程序有明显影响。我们得出结论，DIO3功能对于确保TH在发育中的大脑中发挥作用的适当时间至关重要，并且可能是先前研究中给予TH后观察到对胎儿大脑缺乏影响的主要因素。
