Morrison S, Mitchell L S, Ecob-Prince M S, Griffiths I R, Thomson C E, Barrie J A, Kirkham D
Applied Neurobiology Group, University of Glasgow, UK.
J Neurocytol. 1991 Sep;20(9):769-80. doi: 10.1007/BF01187850.
This study examines the expression of the major myelin protein gene P0 in cultured Schwann cells, grown on their own or in association with neurons. Many freshly dissociated Schwann cells from actively myelinating nerves express Po mRNA in high abundance. If neurons are not present, signal intensity falls markedly with time so that by 7 days in culture only a basal expression is evident which is negligible compared to the level in vivo. Dorsal root ganglia from embryo day 16 (E16) rats contain no significant levels of Po mRNA but when grown in full myelinating medium (containing serum and embryo extract) increasing expression is seen from 4 to 5 days onward even though myelination does not occur until after the second week. In this intervening period the intensity of P0 mRNA expression is lower than that found in the actively myelinating cell. Neurons from sympathetic ganglia are also capable of inducing P0 mRNA expression. Schwann cells in dorsal root ganglia explants grown in serum-free defined medium do not assemble a basal lamina and will not wrap or myelinate axons. Nevertheless P0 mRNA, but not protein, is expressed in levels similar to those found in full myelinating medium prior to myelination. Such Schwann cells also exhibit galactocerebroside and the sulphatide recognised by the 04 antibody. It appears that in defined medium or in myelinating medium prior to myelination axonal signals can induce P0 mRNA expression to a certain degree. However, full up-regulation is usually associated with the rapid membrane expansion accompanying myelination. Whether this augmented up-regulation is due to further axonal signalling or events in the Schwann cell is unknown, but the results suggest that P0 expression can be regulated at several stages of synthesis.
本研究检测了主要髓磷脂蛋白基因P0在单独培养或与神经元共同培养的雪旺细胞中的表达情况。许多从活跃髓鞘化神经中新鲜分离的雪旺细胞大量表达P0 mRNA。如果没有神经元，信号强度会随时间显著下降，以至于在培养7天时，仅能观察到基础表达，与体内水平相比可忽略不计。胚胎第16天（E16）大鼠的背根神经节中不含显著水平的P0 mRNA，但在完全髓鞘化培养基（含血清和胚胎提取物）中培养时，从第4至5天起表达逐渐增加，尽管直到第二周后才发生髓鞘化。在这个间隔期，P0 mRNA表达强度低于活跃髓鞘化细胞中的水平。交感神经节的神经元也能够诱导P0 mRNA表达。在无血清限定培养基中培养的背根神经节外植体中的雪旺细胞不会组装基膜，也不会包裹或髓鞘化轴突。然而，P0 mRNA而非蛋白质的表达水平与髓鞘化前在完全髓鞘化培养基中发现的水平相似。这类雪旺细胞也表现出半乳糖脑苷脂和被04抗体识别的硫脂。看来在限定培养基或髓鞘化前的髓鞘化培养基中，轴突信号可在一定程度上诱导P0 mRNA表达。然而，完全上调通常与髓鞘化伴随的快速膜扩张有关。这种增强的上调是由于进一步的轴突信号传导还是雪旺细胞中的事件尚不清楚，但结果表明P0表达可在合成的几个阶段受到调控。
