Reuner B, Vassella E, Yutzy B, Boshart M
Max-Planck-Institut für Biochemie, Genzentrum, Martinsried, Germany.
Mol Biochem Parasitol. 1997 Dec 1;90(1):269-80. doi: 10.1016/s0166-6851(97)00160-6.
Differentiation from replicating slender forms to non-dividing stumpy bloodstream forms of T. brucei limits the parasite population size in the mammalian host in addition to and independently of the antibody response. Using a culture system for pleomorphic strains of T. brucei we show that slender forms very efficiently differentiate to stumpy forms in vitro and that the induction of differentiation is correlated to cell density. Differentiation in the host and in culture were compared using a battery of markers including cell morphology and volume, cell cycle position, the kinetics of the differentiation, expression of NADH dehydrogenase (diaphorase), expression of several differentially regulated transcripts and the kinetics of transformation to replicating procyclic forms after induction with cis-aconitate. By all available criteria, differentiation in culture reflects the natural process in the mammalian host. Time course experiments reveal a very tight temporal correlation between cell cycle arrest of bloodstream forms, appearance of a stumpy differentiation marker and the competence of a bloodstream form population to initiate transformation to procyclic forms in response to cis-aconitate. Our results show that induction of bloodstream form differentiation can occur independently of host-derived cues. We suggest a density sensing mechanism which induces differentiation to the non-dividing stumpy stage and thereby enables the parasite population to autoregulate its proliferation.
布氏锥虫从增殖性细长型向非分裂性粗短型血流形式的分化，除了抗体反应之外且与之独立，限制了哺乳动物宿主体内寄生虫种群的大小。利用布氏锥虫多形性菌株的培养系统，我们发现细长型在体外能非常高效地分化为粗短型，且分化诱导与细胞密度相关。使用一系列标志物，包括细胞形态和体积、细胞周期位置、分化动力学、NADH脱氢酶（黄递酶）的表达、几种差异调节转录本的表达以及顺乌头酸诱导后向增殖性前循环形式转化的动力学，对宿主体内和培养中的分化进行了比较。根据所有可用标准，培养中的分化反映了哺乳动物宿主体内的自然过程。时间进程实验揭示了血流形式的细胞周期停滞、粗短型分化标志物的出现以及血流形式群体响应顺乌头酸启动向前循环形式转化的能力之间存在非常紧密的时间相关性。我们的结果表明，血流形式分化的诱导可以独立于宿主来源的信号发生。我们提出一种密度感应机制，该机制诱导向非分裂性粗短阶段的分化，从而使寄生虫种群能够自动调节其增殖。
