Cerná Adriana, López-Fernández Carmen, Fernández José Luis, Moreno Díaz de la Espina Susana, de la Torre Consuelo, Gosálvez Jaime
Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu, 9, Madrid, 8040, Spain.
Chromosoma. 2008 Feb;117(1):15-24. doi: 10.1007/s00412-007-0121-9. Epub 2007 Sep 1.
After applying proper deoxyribonucleic acid (DNA) probes, fluorescence in situ hybridization (FISH) showed that the 8/9 centromeres-one per chromatid of the male haploid complement (X0) of Pyrgomorpha conica grasshopper-colocalized at the spermatid blunt end, where the spermatozoa flagellum inserts. A bundle of aligned 4',6-diamidino-2-phenylindole-positive chromatid scaffolds, which formed the central spermatid core, was observed after DNA breakage detection followed by FISH. Modular nature of scaffold DNA was occasionally evident. The technique also showed that in the early spermatid, the chromatid scaffolds lacked any DNA nick, whereas abundant breaks accumulated in the surrounding loops. Moreover, immunodetection showed that scaffold DNA participated in the formation of triplex DNA, while this configuration was absent from the loops. During spermatid maturation, triplex DNA disappeared from the scaffold in parallel with loop retraction, while protamines replace histones. Thus, the presence of triplex DNA in the chromatid scaffold correlates with the anchoring of expanded DNA loops to it. After loop retraction, the scaffolds of all chromatids coiled as a single unit in the spermatid head. This cooperative coiling produced enlargement and tilting of the distal telomeric signals, which were distributed along the spermatid head according to the length of each chromosome. We propose that specific DNA sequences dispersed throughout the whole chromatid fold forward and backward coaxially to chromatid length, forming individual scaffold modules whose linear assembly accounts for the minimum length of each individual chromatid. Finally, the core of the grasshopper male spermatid should be considered as a single chromosome in which the DNA scaffolds of the whole set of the nonhomologous chromosomes of the haploid complement are interconnected. This pattern of chromatin organization applies probably to other elongated spermatids.
应用适当的脱氧核糖核酸（DNA）探针后，荧光原位杂交（FISH）显示，锥头蝗（Pyrgomorpha conica）雄配子单倍体互补组（X0）的每条染色单体上的8个或9个着丝粒，在精子尾部插入的精子细胞钝端共定位。在DNA断裂检测后进行FISH，观察到一束排列整齐的4',6-二脒基-2-苯基吲哚阳性染色单体支架，它们形成了精子细胞的中央核心。支架DNA的模块化性质偶尔也很明显。该技术还表明，在早期精子细胞中，染色单体支架没有任何DNA切口，而周围的环中积累了大量断裂。此外，免疫检测表明，支架DNA参与了三链DNA的形成，而环中不存在这种结构。在精子细胞成熟过程中，随着环的收缩，三链DNA从支架上消失，同时鱼精蛋白取代组蛋白。因此，染色单体支架中三链DNA的存在与扩展的DNA环与之的锚定相关。环收缩后，所有染色单体的支架在精子细胞头部作为一个单一单元盘绕。这种协同盘绕导致远端端粒信号的扩大和倾斜，这些信号根据每条染色体的长度沿着精子细胞头部分布。我们提出，分散在整个染色单体中的特定DNA序列，与染色单体长度同轴向前和向后折叠，形成单个支架模块，其线性组装构成每个染色单体的最小长度。最后，锥头蝗雄性精子细胞的核心应被视为一条单一的染色体，其中单倍体互补组的整套非同源染色体的DNA支架相互连接。这种染色质组织模式可能适用于其他细长的精子细胞。
