Institute of Marine Research, Postboks 1870 Nordnes, 5817, Bergen, Norway.
Reproductive Biology group, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands.
BMC Genomics. 2017 Oct 18;18(1):801. doi: 10.1186/s12864-017-4205-5.
Our understanding of the molecular mechanisms implementing pubertal maturation of the testis in vertebrates is incomplete. This topic is relevant in Atlantic salmon aquaculture, since precocious male puberty negatively impacts animal welfare and growth. We hypothesize that certain miRNAs modulate mRNAs relevant for the initiation of puberty. To explore which miRNAs regulate mRNAs during initiation of puberty in salmon, we performed an integrated transcriptome analysis (miRNA and mRNA-seq) of salmon testis at three stages of development: an immature, long-term quiescent stage, a prepubertal stage just before, and a pubertal stage just after the onset of single cell proliferation activity in the testis.
Differentially expressed miRNAs clustered into 5 distinct expression profiles related to the immature, prepubertal and pubertal salmon testis. Potential mRNA targets of these miRNAs were predicted with miRmap and filtered for mRNAs displaying negatively correlated expression patterns. In summary, this analysis revealed miRNAs previously known to be regulated in immature vertebrate testis (miR-101, miR-137, miR-92b, miR-18a, miR-20a), but also miRNAs first reported here as regulated in the testis (miR-new289, miR-30c, miR-724, miR-26b, miR-new271, miR-217, miR-216a, miR-135a, miR-new194 and the novel predicted n268). By KEGG enrichment analysis, progesterone signaling and cell cycle pathway genes were found regulated by these differentially expressed miRNAs. During the transition into puberty we found differential expression of miRNAs previously associated (let7a/b/c), or newly associated (miR-15c, miR-2184, miR-145 and the novel predicted n7a and b) with this stage. KEGG enrichment analysis revealed that mRNAs of the Wnt, Hedgehog and Apelin signaling pathways were potential regulated targets during the transition into puberty. Likewise, several regulated miRNAs in the pubertal stage had earlier been associated (miR-20a, miR-25, miR-181a, miR-202, let7c/d/a, miR-125b, miR-222a/b, miR-190a) or have now been found connected (miR-2188, miR-144, miR-731, miR-8157 and the novel n2) to the initiation of puberty.
This study has - for the first time - linked testis maturation to specific miRNAs and their inversely correlated expressed targets in Atlantic salmon. The study indicates a broad functional conservation of already known miRNAs and associated pathways involved in the transition into puberty in vertebrates. The analysis also reveals miRNAs not previously associated with testis tissue or its maturation, which calls for further functional studies in the testis.
我们对脊椎动物睾丸青春期成熟的分子机制的理解还不完整。这一主题在大西洋鲑鱼养殖中很重要，因为性早熟会对动物福利和生长产生负面影响。我们假设某些 miRNA 可以调节与青春期开始相关的 mRNA。为了探讨哪些 miRNA 在鲑鱼青春期开始时调节 mRNA，我们对处于三个发育阶段的鲑鱼睾丸进行了整合的转录组分析（miRNA 和 mRNA-seq）：一个不成熟、长期静止的阶段，一个青春期前的阶段，以及一个青春期后的阶段，此时睾丸中的单细胞增殖活动刚刚开始。
差异表达的 miRNA 聚类为 5 个不同的表达谱，与不成熟、青春期前和青春期的鲑鱼睾丸有关。使用 miRmap 预测这些 miRNA 的潜在 mRNA 靶标，并对显示负相关表达模式的 mRNA 进行过滤。总之，这项分析揭示了以前在不成熟的脊椎动物睾丸中被调控的 miRNA（miR-101、miR-137、miR-92b、miR-18a、miR-20a），但也首次报道了在睾丸中被调控的 miRNA（miR-new289、miR-30c、miR-724、miR-26b、miR-new271、miR-217、miR-216a、miR-135a、miR-new194 和新预测的 n268）。通过 KEGG 富集分析，发现孕激素信号和细胞周期途径的基因受到这些差异表达 miRNA 的调控。在进入青春期的过程中，我们发现了先前与该阶段相关（let7a/b/c）或新相关（miR-15c、miR-2184、miR-145 和新预测的 n7a 和 b）的 miRNA 的差异表达。KEGG 富集分析显示，Wnt、Hedgehog 和 Apelin 信号通路的 mRNAs 是进入青春期时潜在的调控靶标。同样，在青春期阶段有几个调控的 miRNA 以前也与青春期的开始有关（miR-20a、miR-25、miR-181a、miR-202、let7c/d/a、miR-125b、miR-222a/b、miR-190a）或现在已经发现与青春期的开始有关（miR-2188、miR-144、miR-731、miR-8157 和新预测的 n2）。
本研究首次将睾丸成熟与大西洋鲑鱼中的特定 miRNA 及其反向相关表达的靶基因联系起来。该研究表明，在脊椎动物的青春期过渡中，已经存在广泛的功能保守的 miRNA 和相关途径。该分析还揭示了以前与睾丸组织或其成熟无关的 miRNA，这需要进一步在睾丸中进行功能研究。
