Abstract：
Chondrichthyes is an important lineage to reconstruct the evolutionary history of vertebrates. Here, we analyzed genome synteny for six chondrichthyan chromosome-level genomes. Our comparative analysis reveals a slow evolutionary rate of chromosomal changes, with infrequent but independent fusions observed in sharks, skates, and chimaeras. The chondrichthyan common ancestor had a proto-vertebrate-like karyotype, including the presence of 18 microchromosome pairs. The X chromosome is a conversed microchromosome shared by all sharks, suggesting a likely common origin of the sex chromosome at least 181 million years ago. We characterized the Y chromosomes of two sharks that are highly differentiated from the X except for a small young evolutionary stratum and a small pseudoautosomal region. We found that shark sex chromosomes lack global dosage compensation but that dosage-sensitive genes are locally compensated. Our study on shark chromosome evolution enhances our understanding of shark sex chromosomes and vertebrate chromosome evolution.
摘要：
软骨是重建脊椎动物进化史的重要谱系。这里,我们分析了6个软骨病染色体水平基因组的基因组同系性。我们的比较分析揭示了染色体变化的进化速度缓慢，在鲨鱼中观察到罕见但独立的融合，溜冰鞋,和嵌合体。软骨病的共同祖先具有类似脊椎动物的核型，包括18个微染色体对的存在。X染色体是所有鲨鱼共享的转换微染色体，这表明至少1.81亿年前性染色体的共同起源。我们表征了两条鲨鱼的Y染色体，它们与X高度分化，除了一个小的年轻进化层和一个小的伪常染色体区域。我们发现鲨鱼性染色体缺乏全局剂量补偿，但剂量敏感基因得到局部补偿。我们对鲨鱼染色体进化的研究增强了我们对鲨鱼性染色体和脊椎动物染色体进化的理解。
