Suja J A, Antonio C, Rufas J S
Departamento de Biología, Facultad de Ciencias C-XV, Universidad Autónoma de Madrid, Spain.
Chromosoma. 1992 Jun;101(8):493-501. doi: 10.1007/BF00352472.
Kinetochores and chromatid cores of meiotic chromosomes of the grasshopper species Arcyptera fusca and Eyprepocnemis plorans were differentially silver stained to analyse the possible involvement of both structures in chromatid cohesiveness and meiotic chromosome segregation. Special attention was paid to the behaviour of these structures in the univalent sex chromosome, and in B univalents with different orientations during the first meiotic division. It was observed that while sister chromatids of univalents are associated at metaphase I, chromatid cores are individualised independently of their orientation. We think that cohesive proteins on the inner surface of sister chromatids, and not the chromatid cores, are involved in the chromatid cohesiveness that maintains associated sister chromatids of bivalents and univalents until anaphase I. At anaphase I sister chromatids of amphitelically oriented B univalents or spontaneous autosomal univalents separate but do not reach the poles because they remain connected at the centromere by a long strand which can be visualized by silver staining, that joins stretched sister kinetochores. This strand is normally observed between sister kinetochores of half-bivalents at metaphase II and early anaphase II. We suggest that certain centromere proteins that form the silver-stainable strand assure chromosome integrity until metaphase II. These cohesive centromere proteins would be released or modified during anaphase II to allow normal chromatid segregation. Failure of this process during the first meiotic division could lead to the lagging of amphitelically oriented univalents. Based on our results we propose a model of meiotic chromosome segregation. During mitosis the cohesive proteins located at the centromere and chromosome arms are released during the same cellular division.(ABSTRACT TRUNCATED AT 250 WORDS)
对草蜢物种深色斧须蝗（Arcyptera fusca）和绿牧草蝗（Eyprepocnemis plorans）减数分裂染色体的动粒和染色单体核心进行了差异银染，以分析这两种结构在染色单体黏连性和减数分裂染色体分离中可能发挥的作用。特别关注了这些结构在单价性染色体以及第一次减数分裂期间具有不同取向的B单价体中的行为。观察到，虽然单价体的姐妹染色单体在中期I时相互关联，但染色单体核心是独立个体化的，与它们的取向无关。我们认为，姐妹染色单体内表面的黏连蛋白而非染色单体核心，参与了维持二价体和单价体的姐妹染色单体相互关联直至后期I的染色单体黏连过程。在后期I，双定向B单价体或自发常染色体单价体的姐妹染色单体分离，但未到达两极，因为它们在着丝粒处通过一条可通过银染可视化的长链相连，该链连接着伸展的姐妹动粒。这条链通常在中期II和后期II早期的半二价体的姐妹动粒之间观察到。我们认为，形成可银染链的某些着丝粒蛋白可确保染色体完整性直至中期II。这些黏连的着丝粒蛋白在后期II期间会被释放或修饰，以允许正常的染色单体分离。第一次减数分裂期间该过程的失败可能导致双定向单价体滞后。基于我们的结果，我们提出了一个减数分裂染色体分离模型。在有丝分裂期间，位于着丝粒和染色体臂上的黏连蛋白在同一细胞分裂过程中被释放。（摘要截选至250词）
