Johnson W B, Ruppe M D, Rockenstein E M, Price J, Sarthy V P, Verderber L C, Mucke L
Department of Neuropharmacology, Scripps Research Institute, La Jolla, California 92037, USA.
Glia. 1995 Mar;13(3):174-84. doi: 10.1002/glia.440130304.
An increase in the expression of the glial fibrillary acidic protein (GFAP) gene by astrocytes appears to constitute a crucial component of the brain's response to injury because it is seen in many different species and features prominently in diverse neurological diseases. Previously, we have used a modified GFAP gene (C-339) to target the expression of beta-galactosidase (beta-gal) to astrocytes in transgenic mice (Mucke et al.; New Biol 3:465-474 1991). To determine to what extent the in vivo expression of GFAP-driven fusion genes is influenced by intragenic GFAP sequences, the E. coli lacZ reporter gene was either placed downstream of approximately 2 kb of murine GFAP 5' flanking region (C-259) or ligated into exon 1 of the entire murine GFAP gene (C-445). Transgenic mice expressing C-259 versus C-445 showed similar levels and distributions of beta-gal activity in their brains. Exclusion of intragenic GFAP sequences from the GFAP-lacZ fusion gene did not diminish injury-induced upmodulation of astroglial beta-gal expression or increase beta-gal expression in non-astrocytic brain cells. These results demonstrate that 2 kb of murine GFAP 5' flanking region is sufficient to restrict transgene expression primarily to astrocytes and to mediate injury-responsiveness in vivo. This sequence therefore constitutes a critical target for mediators of reactive astrocytosis. While acute penetrating brain injuries induced focal increases in beta-gal expression around the lesion sites in C-259, C-445, and C-339 transgenic mice, infection of C-339 transgenic mice with scrapie led to a widespread upmodulation of astroglial beta-gal expression. Hence, GFAP-lacZ transgenic mice can be used to monitor differential patterns of astroglial activation in vivo. These and related models should facilitate the assessment of strategies aimed at the in vivo manipulation of GFAP expression and astroglial activation.
星形胶质细胞中胶质纤维酸性蛋白（GFAP）基因表达的增加似乎是大脑对损伤反应的关键组成部分，因为在许多不同物种中都能观察到这一现象，并且在多种神经疾病中表现突出。此前，我们已使用修饰后的GFAP基因（C-339），将β-半乳糖苷酶（β-gal）的表达靶向转基因小鼠中的星形胶质细胞（Mucke等人；《新生物学》3:465 - 474，1991年）。为了确定GFAP驱动的融合基因的体内表达在多大程度上受基因内GFAP序列的影响，将大肠杆菌lacZ报告基因置于约2 kb的小鼠GFAP 5'侧翼区域（C-259）下游，或将其连接到整个小鼠GFAP基因的外显子1中（C-445）。表达C-259和C-445的转基因小鼠在大脑中显示出相似水平和分布的β-gal活性。从GFAP-lacZ融合基因中排除基因内GFAP序列，并不会减少损伤诱导的星形胶质细胞β-gal表达上调，也不会增加非星形胶质细胞大脑细胞中的β-gal表达。这些结果表明，2 kb的小鼠GFAP 5'侧翼区域足以将转基因表达主要限制在星形胶质细胞中，并在体内介导损伤反应性。因此，该序列构成了反应性星形胶质细胞增生介质的关键靶点。虽然急性穿透性脑损伤在C-259、C-445和C-339转基因小鼠的损伤部位周围引起β-gal表达的局部增加，但用瘙痒病感染C-339转基因小鼠会导致星形胶质细胞β-gal表达的广泛上调。因此，GFAP-lacZ转基因小鼠可用于监测体内星形胶质细胞激活的不同模式。这些及相关模型应有助于评估旨在体内操纵GFAP表达和星形胶质细胞激活的策略。
