Stahl A, Wachtler F, Hartung M, Devictor M, Schöfer C, Mosgöller W, de Lanversin A, Fouet C, Schwarzacher H G
Laboratoire de Génétique, Faculté de Médecine, Marseille, France.
Chromosoma. 1991 Dec;101(4):231-44. doi: 10.1007/BF00365155.
The formation and development of nucleoli and their connections with the nucleolar chromosomes were studied in human spermatocytes using electron microscopy, silver staining of nucleolus organizer regions (NORs), high resolution autoradiography and in situ hybridization in order to localize rRNA genes and their transcription in the different stages of meiotic prophase I. At leptotene, new nucleoli were formed, consisting of a fibrillar centre surrounded by a cap of dense fibrillar component. Following [3H]uridine uptake, label was found only over the dense fibrillar component. In situ hybridization revealed rDNA mainly in the dense fibrillar component and in the chromatin. During zygotene, nucleoli increased in size. The fibrillar centre was connected with the secondary constriction region of the nucleolar bivalent and was partially surrounded by dense fibrillar component. This shell of dense fibrillar component merged into a fibrillo-granular mesh that extended away from the fibrillar centre. Autoradiography following [3H]uridine uptake again showed the label overlaying the dense fibrillar component and the proximal part of the fibrillo-granular strands. With in situ hybridization in both the light and electron microscope, signal was mainly found in the dense fibrillar component. A small quantity of label was observed in the peripheral region of the fibrillar centre and in the adjacent chromatin. From early to late pachytene segregation of nucleolar components occurred, with a reduction in the dense fibrillar component that formed a narrow rim around the fibrillar centre with small extensions along the granular component. [3H]uridine incorporation progressively decreased. In situ hybridization showed signal located mainly in the dense fibrillar component and in the chromatin corresponding to the condensed short arm of the nucleolar bivalent. Our results indicate that the majority of rDNA is located and transcribed in the dense fibrillar component; only a small amount is present in the peripheral part of the fibrillar centre and may be transcribed there. Moreover, from leptotene to zygotene, rDNA unravels from the nucleolar chromosome into the nucleolar dense fibrillar component. From zygotene to late pachytene a progressive return to the condensed acrocentric short arm is observed.
利用电子显微镜、核仁组织区（NORs）银染、高分辨率放射自显影和原位杂交技术，对人类精母细胞中核仁的形成与发育及其与核仁染色体的连接进行了研究，以便在减数分裂前期I的不同阶段定位rRNA基因及其转录情况。细线期时，新的核仁形成，由一个纤维中心及其周围的致密纤维成分帽组成。摄取[3H]尿苷后，标记仅出现在致密纤维成分上。原位杂交显示rDNA主要存在于致密纤维成分和染色质中。偶线期时，核仁体积增大。纤维中心与核仁二价体的次缢痕区域相连，并部分被致密纤维成分包围。这种致密纤维成分的壳融合成一个纤维颗粒网，从纤维中心向外延伸。摄取[3H]尿苷后的放射自显影再次显示标记覆盖在致密纤维成分和纤维颗粒链的近端部分。通过光镜和电镜原位杂交，信号主要出现在致密纤维成分中。在纤维中心的周边区域和相邻染色质中观察到少量标记。从粗线期早期到晚期，核仁成分发生分离，致密纤维成分减少，在纤维中心周围形成一个窄边，并沿着颗粒成分有小的延伸。[3H]尿苷掺入逐渐减少。原位杂交显示信号主要位于致密纤维成分和与核仁二价体浓缩短臂相对应的染色质中。我们的结果表明，大多数rDNA位于致密纤维成分中并在其中转录；只有少量存在于纤维中心的周边部分，可能在那里转录。此外，从细线期到偶线期，rDNA从核仁染色体解旋进入核仁致密纤维成分。从偶线期到粗线期晚期，观察到逐渐回到浓缩的近端着丝粒短臂的过程。
