Programa de Pós-Graduação em Biologia Evolutiva, Laboratório de Genética Evolutiva, Universidade Estadual de Ponta Grossa, Ponta Grossa, Paraná, Brazil.
Programa de Pós-Graduação em Genética Evolutiva e Biologia Molecular, Laboratório de Citogenética de Peixes, Universidade Federal de São Carlos, São Carlos, São Paulo, Brazil.
Zebrafish. 2020 Apr;17(2):147-152. doi: 10.1089/zeb.2019.1756. Epub 2020 Mar 10.
B chromosomes are extra genomic compounds found in different taxonomic groups, including plants and animals. Obtaining patterns of resolutive chromosomal bands is necessary to understand the nuclear organization, variability and nature of B chromosome chromatin and possible transcriptional regions. In this study, we analyzed 35 specimens sampled from Fazenda Lavrinha, a stream in the Paraíba do Sul river basin, Brazil. Through the incorporation of the thymidine analog 5'-bromo-2'-deoxyuridine (5-BrdU) , it was possible to recognize the replicating regions of the B chromosome at the beginning of the S phase, differentially characterized in relationship to the regions of late replication. In this perspective, it is possible to suggest that the B chromosome of this species possesses a territory and the chromatin accessible for transcription, especially in the light (i.e., early replicating) bands (p1.1; p1.3; and p2.1 and q1.1, q1.3, q2.1, and q2.2). The late-replicating regions are corresponding to the blocks of constitutive heterochromatin. They show a preferential accumulation of satellite DNA 51. By the use of the fluorochrome chromomycin A3 (CMA3), it was possible to identify GC-rich chromosomal regions, corresponding to late-replicating parts of genome, confirming the revealed data by the replication banding and C-banding. In addition, the analysis by confocal microscopy in kidney cells indicates the location of a peripheral anchorage of this chromosome in the nuclear lamina, reinforcing the idea of downregulation of the associated regions.
B 染色体是在不同的分类群中发现的额外基因组化合物，包括植物和动物。获得可分辨的染色体带型对于理解 B 染色体染色质和可能的转录区域的核组织、变异性和性质是必要的。在这项研究中，我们分析了来自巴西 Paraíba do Sul 河流域 Lavrinha 农场的 35 个样本。通过掺入胸腺嘧啶类似物 5'-溴-2'-脱氧尿苷（5-BrdU），可以在 S 期开始时识别 B 染色体的复制区域，与晚期复制区域有区别。从这个角度来看，可以推测该物种的 B 染色体具有一个可转录的区域和染色质，特别是在亮带（即早期复制带）（p1.1;p1.3;p2.1 和 q1.1,q1.3,q2.1 和 q2.2）中。晚期复制区域对应于组成型异染色质块。它们表现出卫星 DNA 51 的优先积累。通过使用荧光染料 chromomycin A3（CMA3），可以识别富含 GC 的染色体区域，对应于基因组的晚期复制部分，通过复制带型和 C 带型证实了所揭示的数据。此外，肾脏细胞的共聚焦显微镜分析表明，该染色体在核层中有一个外周锚定位置，这加强了与相关区域下调的想法。
