Muñoz A, Rodriguez-Peña A, Perez-Castillo A, Ferreiro B, Sutcliffe J G, Bernal J
Instituto de Investigaciones Biomédicas C.S.I.C. Facultad de Medicina U.A.M., Madrid, Spain.
Mol Endocrinol. 1991 Feb;5(2):273-80. doi: 10.1210/mend-5-2-273.
To define at the molecular biological level the effects of thyroid hormone on brain development we have examined cDNA clones of brain mRNAs and identified several whose expression is altered in hypothyroid animals during the neonatal period. Clones were identified with probes prepared by subtractive or differential hybridization, and those corresponding to mRNAs altered in hypothyroidism were further studied by Northern blot analysis. Using RNA prepared from whole brains, no effect of hypothyroidism was found on the expression of the astroglial gene coding for glial fibrillary acidic protein. Among genes of neuronal expression, no significant alterations were found in the steady state levels of mRNAs coding for neuron-specific enolase, microtubule-associated protein-2, Tau, or nerve growth factor. N-CAM mRNA increased slightly in hypothyroid brains. In contrast a 2- to 3-fold decrease was found in the mRNA coding for a novel neuronal gene, RC3. This is the first neuronal gene known to be significantly altered at the mRNA level by thyroid hormone deprivation. The abundance of the mRNAs for the major myelin proteins proteolipid protein, myelin basic protein, and myelin-associated glycoprotein, expressed by oligodendrocytes, were also decreased in hypothyroid brains. Developmental studies on RC3 and myelin-associated glycoprotein expression indicated that the corresponding mRNAs accumulate in the brain of normal rats during the first 15-20 days of neonatal life. A similar accumulation occurred in hypothyroid brains, but at much reduced levels. The results demonstrate that thyroid hormone controls the steady state levels of particular mRNAs during brain development.
为了在分子生物学水平上确定甲状腺激素对脑发育的影响，我们检测了脑信使核糖核酸（mRNA）的互补脱氧核糖核酸（cDNA）克隆，并鉴定出了几个在新生期甲状腺功能减退的动物中其表达发生改变的克隆。通过消减杂交或差异杂交制备的探针鉴定出克隆，对于那些在甲状腺功能减退中发生改变的与mRNA相对应的克隆，通过Northern印迹分析进一步研究。使用从全脑制备的RNA，未发现甲状腺功能减退对编码胶质纤维酸性蛋白的星形胶质细胞基因的表达有影响。在神经元表达的基因中，编码神经元特异性烯醇化酶、微管相关蛋白-2、Tau或神经生长因子的mRNA的稳态水平未发现显著改变。在甲状腺功能减退的脑中，神经细胞黏附分子（N-CAM）mRNA略有增加。相反，在编码一种新的神经元基因RC3的mRNA中发现减少了2至3倍。这是已知的第一个在mRNA水平上因甲状腺激素缺乏而发生显著改变的神经元基因。少突胶质细胞表达的主要髓鞘蛋白蛋白脂蛋白、髓鞘碱性蛋白和髓鞘相关糖蛋白的mRNA丰度在甲状腺功能减退的脑中也降低了。对RC3和髓鞘相关糖蛋白表达的发育研究表明，相应的mRNA在新生大鼠出生后的前15至20天内在脑中积累。在甲状腺功能减退的脑中也发生了类似的积累，但水平大大降低。结果表明，甲状腺激素在脑发育过程中控制特定mRNA的稳态水平。
