Wrabetz L, Taveggia C, Feltri M L, Quattrini A, Awatramani R, Scherer S S, Messing A, Kamholz J
DIBIT and Department of Neurology, San Raffaele Scientific Institute, Milano, Italy.
J Neurobiol. 1998 Jan;34(1):10-26. doi: 10.1002/(sici)1097-4695(199801)34:1<10::aid-neu2>3.0.co;2-f.
Previous studies, both in vitro and in vivo, suggest that small portions of the mouse myelin basic protein (MBP) promoter are sufficient to activate regulated expression of MBP. To confirm our previous in vitro studies, we prepared transgenic mice with short regions of the human MBP promoter fused to the lacZ reporter gene. We found that 750 nucleotides of the proximal human MBP promoter is sufficient to activate oligodendrocyte-specific, developmentally regulated expression of lacZ in three independent lines. This promoter, however, does not activate expression of lacZ in Schwann cells in peripheral nerve or in adult mouse brain. The relative levels of beta-galactosidase specific activity, mRNA, and transcription parallel those of MBP mRNA during myelinogenesis. Thus, we exploited this transgene as a quantitative tool to evaluate the response to stimuli known to affect myelination. Transgene expression is reduced 75 % after optic enucleation, as previously reported for levels of MBP mRNA, indicating that axons signal to this portion of the proximal MBP promoter to fully activate MBP expression during myelinogenesis. Instead, in adult shiverer mice, another setting in which MBP transcription is modulated, transgene expression is not increased, in contrast to the increased transcriptional activation of MBP previously reported in these mice. These data suggest that the regulatory region that mediates transcriptional activation of the MBP gene is modular, since discrete subregions are required for activation in Schwann cells, during myelinogenesis in oligodendrocytes, during maintenance myelination in adult brain, and in the dysmyelinating mutant shiverer mouse.
先前的体外和体内研究表明，小鼠髓鞘碱性蛋白（MBP）启动子的小部分足以激活MBP的调控表达。为了证实我们先前的体外研究，我们制备了将人MBP启动子的短区域与lacZ报告基因融合的转基因小鼠。我们发现，人MBP近端启动子的750个核苷酸足以在三个独立的品系中激活少突胶质细胞特异性的、发育调控的lacZ表达。然而，该启动子不会在外周神经的施万细胞或成年小鼠大脑中激活lacZ的表达。在髓鞘形成过程中，β-半乳糖苷酶比活性、mRNA和转录的相对水平与MBP mRNA的水平平行。因此，我们利用这个转基因作为定量工具来评估对已知影响髓鞘形成的刺激的反应。如先前报道的MBP mRNA水平一样，视神经摘除后转基因表达降低了75%，这表明轴突向近端MBP启动子的这一部分发出信号，以在髓鞘形成过程中完全激活MBP表达。相反，在成年颤抖小鼠中，另一种MBP转录受到调节的情况，与先前报道的这些小鼠中MBP转录激活增加相反，转基因表达并未增加。这些数据表明，介导MBP基因转录激活的调控区域是模块化的，因为在施万细胞中、少突胶质细胞髓鞘形成过程中、成年大脑维持髓鞘形成期间以及在脱髓鞘突变颤抖小鼠中，激活需要离散的亚区域。
