Kost-Mikucki S A, Oblinger M M
Department of Cell Biology and Anatomy, Chicago Medical School, IL 60064.
J Neurosci Res. 1991 Feb;28(2):182-91. doi: 10.1002/jnr.490280205.
We examined changes in the expression of glial fibrillary acidic protein (GFAP) mRNA during Wallerian degeneration in the corticospinal system of the adult Golden hamster following axotomy. GFAP is the product of a type III intermediate filament (IF) gene that is expressed specifically in mature astrocytes. A well-studied component of a complex response termed reactive astrogliosis that occurs after various types of CNS injury is the increased production of astrocytic processes filled with GFAP-containing IFs. While increased expression of GFAP during reactive astrogliosis has been well established at the protein level, little is known about whether or not changes in GFAP mRNA levels occur after CNS injury. In the present study we used in situ hybridization methods to examine this issue. A 35S-labeled mouse GFAP cDNA probe was used for in situ hybridizations of sections of the brain stem obtained 2, 7, and 14 days after unilateral transections of the corticospinal tract in the caudal medulla. Film as well as emulsion autoradiography showed a dramatic increase in GFAP mRNA labeling associated with the degenerating corticospinal tract. GFAP mRNA levels were already dramatically increased in the injured corticospinal tract by 2 days post axotomy and remained elevated at 14 days. Interestingly, in addition to the robust increase in GFAP mRNA levels specifically associated with the degenerating tract, a diffuse increase in GFAP mRNA labeling was observed throughout the grey matter of the brain stem at 2 days post-axotomy, but not after this time. Immunoblotting and immunocytochemical experiments verified that the increased GFAP mRNA levels in the degenerating corticospinal system were accompanied by an increased expression of the protein. These results demonstrate that an increase in GFAP mRNA levels occurs during Wallerian degeneration in the CNS and suggest that increased expression of the GFAP gene is a major contributor to CNS scarring that results after direct traumatic injury.
我们研究了成年金黄地鼠皮质脊髓系统在轴突切断后沃勒变性过程中胶质纤维酸性蛋白（GFAP）mRNA表达的变化。GFAP是III型中间丝（IF）基因的产物，在成熟星形胶质细胞中特异性表达。反应性星形胶质化是在各种类型的中枢神经系统损伤后发生的一种复杂反应，其一个经过充分研究的组成部分是充满含GFAP的IF的星形胶质细胞突起的产生增加。虽然在反应性星形胶质化过程中GFAP表达的增加在蛋白质水平上已得到充分证实，但对于中枢神经系统损伤后GFAP mRNA水平是否发生变化却知之甚少。在本研究中，我们使用原位杂交方法来研究这个问题。一个35S标记的小鼠GFAP cDNA探针用于对在延髓尾部单侧切断皮质脊髓束后2天、7天和14天获得的脑干切片进行原位杂交。胶片以及乳胶放射自显影显示，与变性的皮质脊髓束相关的GFAP mRNA标记显著增加。轴突切断后2天，损伤的皮质脊髓束中的GFAP mRNA水平就已显著增加，并在14天时仍保持升高。有趣的是，除了与变性束特异性相关的GFAP mRNA水平的强劲增加外，在轴突切断后2天，在整个脑干灰质中观察到GFAP mRNA标记的弥漫性增加，但在此之后则没有。免疫印迹和免疫细胞化学实验证实，变性的皮质脊髓系统中GFAP mRNA水平的增加伴随着该蛋白表达的增加。这些结果表明，在中枢神经系统的沃勒变性过程中GFAP mRNA水平会升高，并表明GFAP基因表达的增加是直接创伤性损伤后中枢神经系统瘢痕形成的主要原因。
