Timoshevskiy Vladimir A, Timoshevskaya Nataliya, Eşkut Kaan I, Rajandran Kasturi, Smith Jeramiah J
Department of Biology, University of Kentucky, Lexington, KY 40508.
Markey Cancer Center, University of Kentucky, Lexington, KY 40508.
Proc Natl Acad Sci U S A. 2025 Jun 17;122(24):e2421883122. doi: 10.1073/pnas.2421883122. Epub 2025 Jun 12.
Many eukaryotic species undergo programmed elimination of specific chromosomes during embryogenesis, typically retaining these chromosomes only in their germ cells. In some species, programmatic elimination of GRCs, or sex chromosomes, also occurs in a sex-specific manner, with specific chromosomes being transmitted or eliminated by only one sex. As such, these chromosomes provide a unique perspective on the evolution of gene functions that are advantageous to the germline and genetic tradeoffs between somatic vs germline or oocyte vs sperm biology. While GRCs have been extensively characterized in male sea lampreys (), the status of GRCs in females has not yet been resolved, though it has been hypothesized that male-specific expression/transmission of these chromosomes might provide a solution to resolving the long-standing mystery of lamprey sex determining mechanisms. To gain insight into the roles of GRCs in female lampreys, we performed several karyological, transcriptomic, and genomic analyses, which demonstrate that GRCs are present in the female lamprey germline, transmitted by oocytes and somatically eliminated in both sexes. These analyses also show that GRCs play important roles in the maintenance and development of female germline but provide no evidence for sex-specific variation in the elimination and transmission of lamprey GRCs. These findings underscore the diversity of germline functions that are carried out by GRCs in both male and female lampreys and highlight the fact that sex-specific transmission/retention of GRCs likely follows no universal rules across the diverse lineages that have independently evolved to undergo developmentally programmed DNA elimination.
许多真核生物在胚胎发育过程中会经历特定染色体的程序性消除，通常仅在生殖细胞中保留这些染色体。在一些物种中，性染色体（GRCs）的程序性消除也以性别特异性的方式发生，特定染色体仅由一种性别传递或消除。因此，这些染色体为基因功能的进化提供了独特的视角，这些基因功能有利于生殖系以及体细胞与生殖系或卵母细胞与精子生物学之间的遗传权衡。虽然在雄性海七鳃鳗中已对性染色体进行了广泛的表征，但雌性海七鳃鳗中性染色体的情况尚未明确，不过据推测，这些染色体的雄性特异性表达/传递可能为解开七鳃鳗性别决定机制这一长期谜团提供一种解决方案。为了深入了解性染色体在雌性七鳃鳗中的作用，我们进行了多项核型分析、转录组分析和基因组分析，结果表明性染色体存在于雌性七鳃鳗的生殖系中，由卵母细胞传递，并在两性的体细胞中被消除。这些分析还表明，性染色体在雌性生殖系的维持和发育中发挥着重要作用，但没有证据表明七鳃鳗性染色体在消除和传递方面存在性别特异性差异。这些发现强调了性染色体在雄性和雌性七鳃鳗中所执行的生殖系功能的多样性，并突出了一个事实，即性染色体的性别特异性传递/保留在独立进化为经历发育程序性DNA消除的不同谱系中可能没有普遍规律。
