Department of Genetics, Human Genetics Institute of New Jersey, Rutgers University, Piscataway, NJ, USA.
Nat Commun. 2021 Nov 25;12(1):6854. doi: 10.1038/s41467-021-27136-4.
Transposable elements (TEs) must replicate in germline cells to pass novel insertions to offspring. In Drosophila melanogaster ovaries, TEs can exploit specific developmental windows of opportunity to evade host silencing and increase their copy numbers. However, TE activity and host silencing in the distinct cell types of Drosophila testis are not well understood. Here, we reanalyze publicly available single-cell RNA-seq datasets to quantify TE expression in the distinct cell types of the Drosophila testis. We develop a method for identification of TE and host gene expression modules and find that a distinct population of early spermatocytes expresses a large number of TEs at much higher levels than other germline and somatic components of the testes. This burst of TE expression coincides with the activation of Y chromosome fertility factors and spermatocyte-specific transcriptional regulators, as well as downregulation of many components of the piRNA pathway. The TEs expressed by this cell population are specifically enriched on the Y chromosome and depleted on the X chromosome, relative to other active TEs. These data suggest that some TEs may achieve high insertional activity in males by exploiting a window of opportunity for mobilization created by the activation of spermatocyte-specific and Y chromosome-specific transcriptional programs.
转座元件 (TEs) 必须在生殖细胞中复制，才能将新的插入物传递给后代。在黑腹果蝇的卵巢中，TEs 可以利用特定的发育机会窗口来逃避宿主沉默并增加它们的拷贝数。然而，果蝇睾丸中不同细胞类型的 TE 活性和宿主沉默情况尚不清楚。在这里，我们重新分析了公开的单细胞 RNA-seq 数据集，以量化果蝇睾丸中不同细胞类型的 TE 表达。我们开发了一种识别 TE 和宿主基因表达模块的方法，发现一个独特的早期精母细胞群体以比睾丸中其他生殖细胞和体细胞成分高得多的水平表达大量 TE。这种 TE 表达的爆发与 Y 染色体生育因子和精母细胞特异性转录调节剂的激活以及许多 piRNA 途径成分的下调同时发生。与其他活跃的 TE 相比，这个细胞群体表达的 TE 特异性地富集在 Y 染色体上，而在 X 染色体上则缺失。这些数据表明，一些 TEs 可能通过利用由精母细胞特异性和 Y 染色体特异性转录程序激活产生的动员机会窗口，在雄性中实现高插入活性。
