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 Astyanax scabripinnis 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) in vivo, 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 As51. 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.

中文翻译：

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Astyanax scabripinnis（Teleostei：Characidae）肾脏组织细胞中B染色体复制和核定位的动力学。

B染色体是在不同分类组（包括植物和动物）中发现的额外基因组化合物。获得分辨染色体条带的模式对于了解B染色体染色质的核组织，变异性和性质以及可能的转录区域是必要的。在这项研究中，我们分析了从巴西巴西南帕拉伊巴流域Fazenda Lavrinha采集的35个Astyanax scabripinnis标本。通过在体内掺入胸苷类似物5'-溴-2'-脱氧尿苷（5-BrdU），有可能在S期开始时识别B染色体的复制区域，该复制区域与后期复制的区域具有不同的特征。从这个角度来看，可能暗示该物种的B染色体拥有一个区域，并且染色质易于转录，尤其是在轻（即，早期复制）带中（p1.1； p1.3和p2.1）和q1.1，q1.3，q2.1和q2.2）。晚期复制区域对应于组成型异染色质的块。它们显示出卫星DNA As的优先积累51.通过使用荧光染料蓝霉素A3（CMA3），可以鉴定出富含GC的染色体区域，对应于基因组的后期复制部分，并通过复制条带和C条带确认了揭示的数据。另外，通过共聚焦显微镜对肾细胞的分析表明该染色体的周边锚定在核层中的位置，增强了相关区域下调的想法。