Kerrebrock Anne, Flynn Jullien M, Baird Robert B, Hodson Christina N, Ross Laura, Yamashita Yukiko M
Whitehead Institute for Biomedical Research, Cambridge, MA 02142, United States.
Howard Hughes Medical Institute, Cambridge, MA 02138, United States.
G3 (Bethesda). 2025 Sep 3;15(9). doi: 10.1093/g3journal/jkaf155.
Programmed DNA elimination, a phenomenon wherein cells eliminate a subset of genetic material during certain stages of development, is observed in a broad range of organisms. The fungus gnat Bradysia (formerly Sciara) coprophila undergoes a series of programmed DNA elimination events during their development, including elimination of germline-restricted chromosomes (called L chromosomes) in the soma and elimination of paternal chromosomes during male meiosis. However, a lack of understanding surrounding the nature of eliminated chromosomes poses a barrier to studying programmed DNA elimination in this system. Highly repetitive satellite DNA, which often shows chromosome-specific distribution, is a possible candidate for sequences involved in programmed DNA elimination. In this study, we utilized recent genomic data and genome assemblies to identify new satellite DNA sequences of B. coprophila, and characterized their distribution on chromosomes. The results imply that the X and autosomes do not share centromeric satellite DNA sequence (BcopSat-155) with the L chromosomes. We further provide cytological evidence that confirms a recent finding based on the genome assembly that there are 2 distinct L chromosomes that were not previously distinguished cytologically. Together, our work lays a foundation for future studies to explore the possible connection between satellite DNA and the mechanism of programmed DNA elimination in B. coprophila.
程序性DNA消除是一种细胞在发育的特定阶段消除一部分遗传物质的现象，在广泛的生物体中都有观察到。粪蚊（以前称为Sciara）嗜粪菌在其发育过程中经历了一系列程序性DNA消除事件，包括在体细胞中消除生殖系限制染色体（称为L染色体）以及在雄性减数分裂过程中消除父本染色体。然而，对消除染色体的性质缺乏了解成为研究该系统中程序性DNA消除的障碍。高度重复的卫星DNA通常表现出染色体特异性分布，是参与程序性DNA消除的序列的可能候选者。在这项研究中，我们利用最近的基因组数据和基因组组装来鉴定嗜粪菌的新卫星DNA序列，并表征它们在染色体上的分布。结果表明，X染色体和常染色体与L染色体不共享着丝粒卫星DNA序列（BcopSat-155）。我们进一步提供了细胞学证据，证实了基于基因组组装的最近一项发现，即存在2条不同的L染色体，以前在细胞学上未被区分。总之，我们的工作为未来研究探索卫星DNA与嗜粪菌程序性DNA消除机制之间的可能联系奠定了基础。
