Molecular basis of cellular functions in Dictyostelium

(1)利用良好的细胞同步方法和双转化盘基骨柱细胞群体，已经证明了饥饿时ceII周期位置与随后尖端分化标记的表达之间存在很强的相关性。在G2期极晚期饥饿的cei细胞选择性地分化为尖端前柄细胞，而G2期中后期饥饿的细胞则分化为后前孢子细胞。因此，细胞周期阶段和位置信息的结合决定了细胞的命运。(2) Nocodazole或calyculin a处理的ceii在早期聚集（丘）期周围生长明显受到抑制，形态发生异常，形成棒状多细胞结构，孢子前分化受到极大抑制。因此，围绕丘期的细胞周期进程似乎是孢子前分化所必需的。(3)饥饿反应的信号已被证明是通过升高的[Ca^<2+>] i来转导的。此外，还发现了一些与饥饿反应有关的磷酸化蛋白。(4)分离并鉴定了盘基骨柱细胞从生长到分化过程中特异性表达的3个基因。(5) Dictyostelium iqgap相关蛋白已被证实特异性参与细胞质分裂的完成。此外，肌动蛋白丝的滑动被发现受到Dictyostelium myosin ii中SH2胱氨酸突变的极大调节。

(1) Using the good method for cell synchnony and doubly transformed Dictyostelium cell populations, it has been demonstrated that there is a strong correlation between ceII cycle position at the time of starvation and subsequent expression of a marker of tip differentiation. CeIIs starved in very late-G2 phase selectively differentiated into tip prestalk cells, while cells starved in mid-late G2 phase into the posterior prespore cells. Thus a combination of cell cycle stage and positional information dictates cell fate.(2) Nocodazole- or calyculin A-treated ceIIs, whose growth around the early aggregate (mound) stage was markedly inhibited, exhibited abnormal morphogenesis to form a stick-like multicellular structure, and prespore differentiation was greatly suppressed. Accordingly, the cell-cycle progression around the mound stage seems to be required for prespore differentiation.(3) The signals for starvation response have been shown to be transduced through elevated [Ca^<2+>] i. Also, some phosphoproteins responsible for starvation response were found.(4) Three genes ware isolated and identified as ones specifically expressed during the transition of Dictyostelium cells from growth to differentiation.(5) Dictyostelium IQGAP-related protein has been shown to be specifically involved in the completion of cytokinesis. In addition, sliding of actin filaments was found to be greatly modulated by mutations of the SH2 cystcine in Dictyostelium myosin ll.