Carey M B, Matsumoto S G
Department of Biological Structure and Function, Oregon Health Sciences University, Portland, Oregon 97201, USA.
Dev Biol. 1999 Nov 15;215(2):298-313. doi: 10.1006/dbio.1999.9433.
We have shown that cultured mouse neural crest (NC) cells exhibit transient increases in intracellular calcium. Up to 50% of the cultured NC-derived cells exhibited calcium transients during the period of neuronal differentiation. As neurogenic activity declined, so did the percentage of active NC-derived cells and their calcium spiking frequency. The decrease in calcium transient activity correlated with a decreased sensitivity to thimerosal, which sensitizes inositol 1,4,5-triphosphate receptors. Thimerosal increased the frequency of oscillations in active NC-derived cells and induced them in a subpopulation of quiescent cells. As neurogenesis ended, NC-derived cells became nonresponsive to thimerosal. Using the expression of time-dependent neuronal traits, we determined that neurons exhibited spontaneous calcium transients as early as a neuronal phenotype could be detected and continued through the acquisition of caffeine sensitivity, soon after which calcium transient activity stopped. A subpopulation of nonneuronal NC-derived cells exhibited calcium transient activity within the same time frame as neurogenesis in culture. Exposing NC-derived cells to 20 mM Mg(2+) blocked calcium transient activity and reduced neuronal number without affecting the survival of differentiated neurons. Using lineage-tracing analysis, we found that 50% of active NC-derived cells gave rise to clones containing neurons, while inactive cells did not. We hypothesize that calcium transient activity establishes a neuronal competence for undifferentiated NC cells.
我们已经表明，培养的小鼠神经嵴（NC）细胞表现出细胞内钙的短暂增加。在神经元分化期间，高达50%的培养的NC衍生细胞表现出钙瞬变。随着神经源性活动的下降，活跃的NC衍生细胞的百分比及其钙尖峰频率也随之下降。钙瞬变活动的减少与对硫柳汞的敏感性降低相关，硫柳汞可使肌醇1,4,5-三磷酸受体敏感化。硫柳汞增加了活跃的NC衍生细胞中的振荡频率，并在静止细胞亚群中诱导出振荡。随着神经发生结束，NC衍生细胞对硫柳汞变得无反应。利用时间依赖性神经元特征的表达，我们确定神经元早在能够检测到神经元表型时就表现出自发性钙瞬变，并持续到获得咖啡因敏感性之后不久，此后钙瞬变活动停止。非神经元NC衍生细胞的一个亚群在与培养中的神经发生相同的时间框架内表现出钙瞬变活动。将NC衍生细胞暴露于20 mM Mg(2+)可阻断钙瞬变活动并减少神经元数量，而不影响分化神经元的存活。通过谱系追踪分析，我们发现50%的活跃NC衍生细胞产生了包含神经元的克隆，而不活跃的细胞则没有。我们假设钙瞬变活动为未分化的NC细胞建立了神经元能力。
