Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115.
Department of Genetics, Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem 91904, Israel.
Genetics. 2018 Oct;210(2):587-605. doi: 10.1534/genetics.118.301315. Epub 2018 Aug 9.
Developmental programs are executed by tightly controlled gene regulatory pathways. Here, we combined the unique sample retrieval capacity afforded by laser capture microscopy with analysis of mRNA abundance by CEL-Seq (cell expression by linear amplification and sequencing) to generate a spatiotemporal gene expression map of the syncytial germline from adult hermaphrodites and males. We found that over 6000 genes exhibit spatiotemporally dynamic expression patterns throughout the hermaphrodite germline, with two dominant groups of genes exhibiting reciprocal shifts in expression at late pachytene during meiotic prophase I. We found a strong correlation between restricted spatiotemporal expression and known developmental and cellular processes, indicating that these gene expression changes may be an important driver of germ cell progression. Analysis of the male gonad revealed a shift in gene expression at early pachytene and upregulation of subsets of genes following the meiotic divisions, specifically in early and late spermatids, mostly transcribed from the X chromosome. We observed that while the X chromosome is silenced throughout the first half of the gonad, some genes escape this control and are highly expressed throughout the germline. Although we found a strong correlation between the expression of genes corresponding to CSR-1-interacting 22G-RNAs during germ cell progression, we also found that a large fraction of genes may bypass the need for CSR-1-mediated germline licensing. Taken together, these findings suggest the existence of mechanisms that enable a shift in gene expression during prophase I to promote germ cell progression.
发育程序是通过紧密控制的基因调控途径来执行的。在这里,我们将激光捕获显微镜提供的独特样本检索能力与 CEL-Seq(通过线性扩增和测序进行细胞表达)分析相结合,生成了来自雌雄同体和雄性的合胞生殖系的时空基因表达图谱。我们发现,超过 6000 个基因在整个雌雄同体生殖系中表现出时空动态表达模式,其中两组主要的基因在减数分裂前期 I 的晚粗线期表现出表达的相互转换。我们发现,限制时空表达与已知的发育和细胞过程之间存在很强的相关性,表明这些基因表达变化可能是生殖细胞进展的重要驱动因素。对雄性性腺的分析表明,在早期粗线期发生了基因表达的转变,并且在减数分裂后,亚组基因的表达上调,特别是在早期和晚期精母细胞中,这些基因主要从 X 染色体转录。我们观察到,虽然 X 染色体在性腺的前半部分一直处于沉默状态,但一些基因逃脱了这种控制,并在整个生殖系中高度表达。虽然我们发现了在生殖细胞进展过程中 CSR-1 相互作用的 22G-RNAs 表达之间存在很强的相关性,但我们也发现很大一部分基因可能绕过 CSR-1 介导的生殖系许可的需要。总之,这些发现表明存在一些机制,可以在减数分裂前期 I 期间促进基因表达的转变,从而促进生殖细胞的进展。