Lee M, Brennan A, Blanchard A, Zoidl G, Dong Z, Tabernero A, Zoidl C, Dent M A, Jessen K R, Mirsky R
Department of Anatomy and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, England.
Mol Cell Neurosci. 1997;8(5):336-50. doi: 10.1006/mcne.1996.0589.
We show that in the rat, the major gene of PNS myelin, P0, is expressed long before myelination in the neural crest, Schwann cell precursors, and embryonic Schwann cells irrespective of whether they will myelinate or not. This myelin-independent P0 expression is constitutive and likely to serve as a specific marker for the Schwann cell lineage. The much higher P0 expression accompanying myelination is therefore not new gene expression but strong up-regulation of preexisting basal levels. We provide new evidence that the up-regulation to myelination-related levels depends on positive extrinsic signals and therefore does not represent a constitutive phenotype. P0 mRNA is not detectable in mature non-myelin-forming Schwann cells of the sympathetic trunk, but is detectable after transection, indicating that there is a P0-inhibitory signal associated with mature unmyelinated axons. Thus, the regulation of the P0 gene is complex, encompassing extrinsically signaled amplification superimposed on a highly lineage-specific and constitutive basal expression.
我们发现，在大鼠中，周围神经系统髓鞘的主要基因P0早在神经嵴、雪旺细胞前体和胚胎雪旺细胞中髓鞘形成之前就已表达，无论它们是否会形成髓鞘。这种与髓鞘形成无关的P0表达是组成性的，可能作为雪旺细胞谱系的特异性标志物。因此，伴随髓鞘形成的更高水平的P0表达并非新基因表达，而是已有基础水平的强烈上调。我们提供了新的证据，表明上调至与髓鞘形成相关的水平依赖于正向的外在信号，因此并不代表组成性表型。在交感干成熟的非髓鞘形成雪旺细胞中检测不到P0 mRNA，但在横断后可检测到，这表明存在与成熟无髓鞘轴突相关的P0抑制信号。因此，P0基因的调控是复杂的，包括外在信号介导的扩增叠加在高度谱系特异性和组成性的基础表达之上。
