Department of Computer Science and Engineering, University of Texas at Arlington, Arlington, TX 76019, USA.
Department of Biology, University of Texas at Arlington, Arlington, TX 76019, USA.
Genome Biol Evol. 2024 Mar 2;16(3). doi: 10.1093/gbe/evae059.
Spermatogenesis is critical to sexual reproduction yet evolves rapidly in many organisms. High-throughput single-cell transcriptomics promises unparalleled insight into this important process but understanding can be impeded in nonmodel systems by a lack of known genes that can reliably demarcate biologically meaningful cell populations. Tribolium castaneum, the red flour beetle, lacks known markers for spermatogenesis found in insect species like Drosophila melanogaster. Using single-cell sequencing data collected from adult beetle testes, we implement a strategy for elucidating biologically meaningful cell populations by using transient expression stage identification markers, weighted principal component clustering, and SNP-based haploid/diploid phasing. We identify populations that correspond to observable points in sperm differentiation and find species specific markers for each stage. Our results indicate that molecular pathways underlying spermatogenesis in Coleoptera are substantially diverged from those in Diptera. We also show that most genes on the X chromosome experience meiotic sex chromosome inactivation. Temporal expression of Drosophila MSL complex homologs coupled with spatial analysis of potential chromatin entry sites further suggests that the dosage compensation machinery may mediate escape from meiotic sex chromosome inactivation and postmeiotic reactivation of the X chromosome.
精子发生对于有性生殖至关重要，但在许多生物体中进化迅速。高通量单细胞转录组学有望为这一重要过程提供无与伦比的洞察力，但在非模式系统中，由于缺乏可靠地标定生物学意义上的细胞群体的已知基因，理解可能会受到阻碍。赤拟谷盗（Tribolium castaneum）缺乏像黑腹果蝇（Drosophila melanogaster）等昆虫物种中已知的精子发生标记物。我们使用从成年甲虫睾丸中收集的单细胞测序数据，通过使用瞬时表达阶段鉴定标记物、加权主成分聚类和基于 SNP 的单倍体/二倍体分相，实施了一种阐明生物学意义上的细胞群体的策略。我们确定了与精子分化中可观察到的点相对应的群体，并为每个阶段找到了特定于物种的标记物。我们的结果表明，鞘翅目动物精子发生的分子途径与双翅目动物的途径有很大的不同。我们还表明，X 染色体上的大多数基因都经历减数分裂性染色体失活。果蝇 MSL 复合物同源物的时空表达以及潜在染色质进入位点的空间分析进一步表明，剂量补偿机制可能介导减数分裂性染色体失活的逃逸和 X 染色体的减数后再激活。
