Mompart Florence, Robelin David, Delcros Chantal, Yerle-Bouissou Martine
INRA, UMR 444, Génétique Cellulaire, F-31326 Castanet, Tolosan, France.
BMC Cell Biol. 2013 Jun 26;14:30. doi: 10.1186/1471-2121-14-30.
While the essential role of 3D nuclear architecture on nuclear functions has been demonstrated for various cell types, information available for neutrophils, essential components of the immune system, remains limited. In this study, we analysed the spatial arrangements of telomeres which play a central role in cell fate. Our studies were carried out in swine, which is an excellent model organism for both biomedical research and agronomic applications. We isolated bacterial artificial chromosome (BAC)-containing subtelomeric p and q sequences specific to each porcine chromosome. This allowed us to study the behaviour of p and q telomeres of homologous chromosomes for seven pairs chosen for their difference in length and morphology. This was performed using 3D-FISH on structurally preserved neutrophils, and confocal microscopy. Resting and lipopolysaccharide (LPS)-activated states were investigated to ascertain whether a response to a pathogen aggression modifies this organization.
The positions of the p and q telomeres relative to the nuclear outer border were determined in the two states. All p telomeres changed their position significantly during the activation process, although the effect was less pronounced for the q telomeres. The patterns of telomeric associations between homologs and their frequencies were analysed for 7 pairs of chromosomes. This analysis revealed that the distribution of pp, qq and pq associations differs significantly among the 7 chromosomes. This distribution does not fit with the theoretical distribution for each chromosome, suggesting that preferential associations occur between subtelomeres.
The percentage of nuclei harbouring at least one telomeric association between homologs varies significantly among the chromosomes, the smallest metacentric chromosome SSC12, which is also the richest in gene-density, harbouring the highest value. The distribution of types of telomeric associations is highly dependent on the chromosomes and is not affected by the activation process. The frequencies of telomeric associations are also highly dependent on the type of association and the type of chromosome. Overall, the LPS-activation process induces only minor changes in these patterns of associations. When telomeric associations occur, the associations of p and q arms from the same chromosome are the most frequent, suggesting that "chromosome bending" occurs in neutrophils as previously observed in gametes.
虽然三维核结构在各种细胞类型的核功能中所起的重要作用已得到证实，但关于免疫系统的重要组成部分中性粒细胞的现有信息仍然有限。在本研究中，我们分析了在细胞命运中起核心作用的端粒的空间排列。我们的研究在猪身上进行，猪是生物医学研究和农业应用的优秀模式生物。我们分离出了包含特定于每条猪染色体的细菌人工染色体（BAC）的亚端粒p和q序列。这使我们能够研究因长度和形态不同而挑选出的七对同源染色体的p和q端粒的行为。这是通过对结构保存的中性粒细胞进行三维荧光原位杂交（3D-FISH）以及共聚焦显微镜来完成的。研究了静息状态和脂多糖（LPS）激活状态，以确定对病原体侵袭的反应是否会改变这种组织形式。
在两种状态下确定了p和q端粒相对于核外边界的位置。在激活过程中，所有p端粒的位置都发生了显著变化，尽管q端粒的变化不太明显。分析了7对染色体同源物之间的端粒关联模式及其频率。该分析表明，pp、qq和pq关联的分布在7条染色体之间存在显著差异。这种分布不符合每条染色体的理论分布，表明亚端粒之间存在优先关联。
同源物之间至少存在一个端粒关联的细胞核百分比在各染色体之间差异显著，最小的中着丝粒染色体SSC12（其基因密度也最高）的这一百分比最高。端粒关联类型的分布高度依赖于染色体，且不受激活过程的影响。端粒关联的频率也高度依赖于关联类型和染色体类型。总体而言，LPS激活过程仅在这些关联模式中引起微小变化。当发生端粒关联时，来自同一染色体的p和q臂的关联最为频繁，这表明中性粒细胞中会出现“染色体弯曲”，正如之前在配子中观察到的那样。
