Department of Anatomy, Institute of Physiological and Anatomical Medicine, Tzu Chi University, Hualien, Taiwan.
J Anat. 2010 Apr;216(4):525-32. doi: 10.1111/j.1469-7580.2009.01204.x. Epub 2010 Jan 27.
Extensive morphological modification occurs during mammalian spermiogenesis when spermatids change their spherical shape into cells with a compact head and a long tail. In this study, freeze-fracture was used to elucidate the alteration of the nuclear envelope during this process. Nuclear condensation resulted in a great reduction of spermatid nuclear volume and the formation of the redundant nuclear envelope. During nuclear condensation, distribution patterns of nuclear pores were greatly affected by the developing acrosome and manchette. As the acrosome enlarged to cap the nucleus, the pores redistributed caudally in the nuclear membranes and became exclusively localized to the redundant nuclear envelope. Manchette microtubules play an important role in shaping the nucleus, and formation of the manchette was associated with exclusion of nuclear pores from the underlying nuclear envelope; therefore, it is likely that the redistribution of nuclear pores was aided by manchette development. The appearance of an electron-lucent nuclear region surrounded by the nascent redundant nuclear envelope indicated a pathway for transporting degradation products through the nuclear pores to the residual cytoplasm. The packaging of the nuclear pores into the redundant nuclear envelope suggests that they play a role in late stages of sperm maturation or in fertilization, as most other unnecessary organelles of sperm are discarded during spermiogenesis or during shedding of the cytoplasmic droplet.
在哺乳动物精子发生过程中，精子细胞经历广泛的形态修饰，从球形变为具有紧凑头部和长尾巴的细胞。在这项研究中，使用冷冻断裂来阐明核膜在这个过程中的变化。核浓缩导致精子细胞核体积大大减小，并形成多余的核膜。在核浓缩过程中，核孔的分布模式受到不断发育的顶体和顶体囊的极大影响。随着顶体扩大覆盖核，核膜中的核孔向尾部重新分布，并专门定位于多余的核膜上。顶体囊微管在塑造核方面发挥着重要作用，顶体囊的形成与核膜下核孔的排除有关；因此，核孔的重新分布可能是由顶体囊的发育辅助的。由新生的多余核膜包围的电子透明核区的出现表明了一种通过核孔将降解产物运输到残留细胞质的途径。核孔被包装到多余的核膜中表明它们在精子成熟的后期或受精过程中发挥作用，因为在精子发生过程或细胞质滴脱落过程中，精子的大多数其他不必要的细胞器都会被丢弃。
