Uno S, Abé S
Department of Biology, Faculty of Science, Kumanoto University, Japan.
Exp Cell Res. 1990 Feb;186(2):279-87. doi: 10.1016/0014-4827(90)90307-v.
In order to elucidate mechanisms that control flagellar length of mature sperm, we studied in synchronous cell suspension cultures flagellar growth, tubulin pool, and tubulin synthesis in round spermatids of Xenopus laevis and the newt Cynops pyrrhogaster. The average final length of flagella in Xenopus round spermatids was 35 mum, almost the same length as that in mature sperm, whereas in the newt round spermatids, the length was 210 mum, almost half that of mature sperm. Kinetics of flagellar growth showed that the rate and period of flagellar growth in the newt spermatids were two to threefold those in Xenopus spermatids. The tubulin pool size in newt spermatids was estimated to be about 10-fold greater than that in Xenopus spermatids. But even if all of the pool was used for flagellar growth, it could support only about a seventh to a tenth of the flagellar length in mature sperm in either species. Thus, the possibility that the tubulin pool primarily determines flagellar length was excluded. Since the tubulin pool size did not change throughout the culture period, the possibility that the termination of flagellar growth is due to the exhaustion of the tubulin pool was also excluded. Tubulin synthesis declined over the culture period but continued in newt spermatids longer than in Xenopus spermatids. The period of flagellar elongation almost coincided with the period of tubulin synthesis. The amount of rRNA did not decrease, excluding the possibility that the decline of tubulin synthesis was due to cytoplasmic shedding which might result in the loss of ribosomes. Tubulin synthesis and the amount of rRNA in newt spermatids was more than threefold greater than that in Xenopus spermatids, which may explain the difference in growth rates of their flagella.
为了阐明控制成熟精子鞭毛长度的机制，我们在非洲爪蟾和东方蝾螈的圆形精子细胞同步化细胞悬浮培养物中研究了鞭毛生长、微管蛋白库和微管蛋白合成。非洲爪蟾圆形精子细胞中鞭毛的平均最终长度为35μm，几乎与成熟精子的长度相同，而在蝾螈圆形精子细胞中，长度为210μm，几乎是成熟精子长度的一半。鞭毛生长动力学表明，蝾螈精子细胞中鞭毛生长的速率和周期是非洲爪蟾精子细胞的两到三倍。据估计，蝾螈精子细胞中的微管蛋白库大小比非洲爪蟾精子细胞中的大约大10倍。但即使所有的微管蛋白库都用于鞭毛生长，在这两个物种中，它也只能支持成熟精子中约七分之一到十分之一的鞭毛长度。因此，微管蛋白库主要决定鞭毛长度的可能性被排除。由于在整个培养期间微管蛋白库大小没有变化，鞭毛生长终止是由于微管蛋白库耗尽的可能性也被排除。在培养期间微管蛋白合成下降，但在蝾螈精子细胞中持续的时间比在非洲爪蟾精子细胞中长。鞭毛伸长的时期几乎与微管蛋白合成的时期一致。rRNA的量没有减少，排除了微管蛋白合成下降是由于可能导致核糖体丢失的细胞质脱落的可能性。蝾螈精子细胞中的微管蛋白合成和rRNA的量比非洲爪蟾精子细胞中的大三倍多，这可能解释了它们鞭毛生长速率的差异。
