背景:位于端粒和染色体体之间的基因组区域,被称为端粒下,是异色的,repeat-rich,并经常进行重新安排。在这个区域内,大规模的结构变化使基因多样化,and,因此,大的多拷贝基因家族通常在端粒下发现。在一些寄生虫中,与增殖相关的基因,入侵,通常在这些地区找到生存,它们受益于端粒的高度可塑性,快速变化的自然。完整(或接近完整)寄生虫基因组的日益增加的可用性提供了一个机会来研究这些通常定义不清和被忽视的基因组区域,并可能揭示寄生虫生活方式所必需的相关基因家族。
结果:使用最新的染色体尺度基因组组装和在染色体末端观察到的标志重复丰富度,我们已经鉴定并表征了曼氏血吸虫的亚端粒,一种后生寄生扁虫,感染全球超过2.5亿人。大约12%的曼索尼基因组被归类为亚端粒,and,与其他生物一致,我们发现这些区域基因贫乏,但富含转座因子。我们发现S.mansoni亚端粒已经经历了广泛的染色体间重组,并且这些位点不成比例地贡献了来自片段重复的基因组的2.3%。这种重组导致了包含103个基因的亚端粒基因簇的扩展,包括免疫调节膜联蛋白和其他作用未知的基因家族。其中最大的是含有49个拷贝的丛蛋白结构域的蛋白质簇,仅在皮膜-位于宿主-寄生虫物理界面的组织中表达。
结论:我们建议亚端粒区充当基因复制和随后分歧的试错的基因组游乐场。由于亚端粒基因在其他寄生虫中的重要性,与曼森氏杆菌内的这种亚端粒扩增有关的基因家族需要进一步表征其在寄生中的潜在作用。
BACKGROUND: The genomic region that lies between the telomere and chromosome body, termed the subtelomere, is heterochromatic, repeat-rich, and frequently undergoes rearrangement. Within this region, large-scale structural changes enable gene diversification, and, as such, large multicopy gene families are often found at the subtelomere. In some parasites, genes associated with proliferation, invasion, and survival are often found in these regions, where they benefit from the subtelomere\'s highly plastic, rapidly changing nature. The increasing availability of complete (or near complete) parasite genomes provides an opportunity to investigate these typically poorly defined and overlooked genomic regions and potentially reveal relevant gene families necessary for the parasite\'s lifestyle.
RESULTS: Using the latest chromosome-scale genome assembly and hallmark repeat richness observed at chromosome termini, we have identified and characterised the subtelomeres of Schistosoma mansoni, a metazoan parasitic flatworm that infects over 250 million people worldwide. Approximately 12% of the S. mansoni genome is classified as subtelomeric, and, in line with other organisms, we find these regions to be gene-poor but rich in transposable elements. We find that S. mansoni subtelomeres have undergone extensive interchromosomal recombination and that these sites disproportionately contribute to the 2.3% of the genome derived from segmental duplications. This recombination has led to the expansion of subtelomeric gene clusters containing 103 genes, including the immunomodulatory annexins and other gene families with unknown roles. The largest of these is a 49-copy plexin domain-containing protein cluster, exclusively expressed in the tegument-the tissue located at the host-parasite physical interface-of intramolluscan life stages.
CONCLUSIONS: We propose that subtelomeric regions act as a genomic playground for trial-and-error of gene duplication and subsequent divergence. Owing to the importance of subtelomeric genes in other parasites, gene families implicated in this subtelomeric expansion within S. mansoni warrant further characterisation for a potential role in parasitism.