Apoptosis-inducing effect of ribosomal protein L4 during neurogenesis and aging

采用RT-PCR和原位杂交技术检测rpL4在大鼠脑发育过程中的表达和分布。rpL4mRNA在胚胎和新生儿（至出生后14天）大脑的高细胞增殖区域有显著表达。提示rpL4可能在胎儿和新生儿大脑细胞增殖和细胞死亡中起一定作用。第13天给予大鼠胚胎5-氮杂胞苷（5AzC），观察脑内细胞凋亡和rpL4 mRNA表达。9时观察脑组织细胞凋亡。5AzC给药后24小时。然而，rpL4 mRNA的表达水平在此期间没有变化。采用免疫组织化学和RT-PCR检测5azc处理大鼠胚胎脑中p53、P21、bax、cyclin G1、’fas和gadd 45的表达。用BrdU标记法检测细胞增殖水平。在给药5次azc后12小时、9小时和12小时，tunel阳性凋亡细胞、p53阳性凋亡细胞和p21阳性凋亡细胞的数量达到最大，且这些细胞分布在相同的区域。通过RT-PCR检测，p21（9 ~ 12小时）、bax（12小时）、cyclin G1（9 ~ 24小时）和fas（9 ~ 12小时）的表达均较对照显著升高。5azc给药后12小时brdu阳性细胞数量明显减少，表明细胞周期G1阻滞。研究结果阐明了5azc给药后rpL4 mRNA表达的细节，以及随后DNA损伤和凋亡的机制。在老化过程中同样的检查正在进行。

The expression and distribution of rpL4 during rat brain development were examined by RT-PCR and in situ hybridization techniques. Marked expression of rpL4mRNA observed in the areas of high cellular proliferation in the brian of embryos and neonates (up to postnatal day 14). It is suggested that rpL4 would have certain roles involved in cell proliferation and cell death in the fetal and neonatal brain. Rat embryos were administered with 5-Azacytidine (5AzC) at day 13 and apoptosis and rpL4 mRNA expression in the brain were investigated. Brain cell apoptosis was observed at.9.to 24 hr after 5AzC administration. The level of rpL4 mRNA expression, however, did not change during this period.The expression of p53, P21, bax, cyclin G1, 'fas and gadd 45 in the 5AzC-treated rat embryonal brain was examined by immunohistochemistry and RT-PCR. Cell proliferation level was also examined by BrdU labeling. The number of TUNEL-positive apoptotic cells, p53-positive cells, and p21-positive cells were at the maximum level at 12 hr, 9 hr and 12 hr after 5 AzC-administration, respectively, and these cells were observed at the same areas. By RT-PCR, the expression of p21 (at 9 to 12 hr), bax (at 12 hr), cyclin G1 (at 9 to 24 hr), and fas (at 9 to 12 hr) was markedly increased compared with control. The number of BrdU-positive cells was markedly decreased at 12 hr after 5AzC-administration, indicating G1 arrest of the cell cycle.The results of the study clarified details of the rpL4 mRNA expression, and the mechanism of subsequent DNA damage and apoptosis, after 5AzC-administration. Same examination during the aging process is now going on.