Kleppe Lene, Wargelius Anna, Johnsen Hanne, Andersson Eva, Edvardsen Rolf B
Institute of Marine Research, P. O. Box 1870 Nordnes, 5817 Bergen, Norway.
Nofima, Muninbakken 9-13, N-9291 Tromsø, Norway.
Gene. 2015 Apr 15;560(2):217-25. doi: 10.1016/j.gene.2015.02.008. Epub 2015 Feb 7.
Atlantic salmon is a commercially important species. Understanding key processes in their life history, such as germ cell development is essential for further improvements within salmon farming. Since salmonids have undergone an additional whole genome duplication compared to many other fish species, they possess more gene paralogues. Therefore, data on gene expression and function from other species may not apply for salmon. Our aim was to study the spatial and tissue specific expression of genes known from model species to be essential for germ cell development, to identify germ cell specific factors in salmon. Based on homology with other species, selected genes were predicted in the salmon genome assembly. Gene expression was measured by PCR in a variety of juvenile salmon tissues. For genes expressed exclusively in gonads we measured the expression in the same tissues as well as in eggs, embryos and larvae by qPCR. Finally, we revealed the cellular localization of the gonad specific mRNAs by in situ hybridization (ISH). Several of the selected genes (tdrd7, cxcr4b and dazl), were found in more than one copy (indicated by a number following the gene name) in the salmon genome. Expression of tdrd7-2, dazl-2, piwil1 and tdrd1 was detected exclusively in the testis and ovary of juvenile salmon, and transcripts of tdrd7-2, dazl-2 and piwil1 were localized within male and female germ cells. While tdrd7-2, piwil1 and tdrd1 were expressed in unfertilized eggs and all embryo and larval stages measured, dazl-2 was expressed in unfertilized eggs and embryos until the onset of gastrulation. This study shows that several of the genes known from model species to be essential for germ cell development, display paralogues in salmon with dissimilar and similar expression patterns in comparison to other species. Transcripts of tdrd7-2, dazl-2, piwil1 and tdrd1 are detected exclusively in gonads of juveniles and are found among maternal RNA of eggs and subsequent embryos. This information is valuable for further studies aiming at understanding salmon germ cell development.
大西洋鲑是一种具有重要商业价值的物种。了解其生命历程中的关键过程，如生殖细胞发育，对于鲑鱼养殖的进一步改进至关重要。由于鲑科鱼类与许多其他鱼类相比经历了一次额外的全基因组复制，它们拥有更多的基因旁系同源物。因此，来自其他物种的基因表达和功能数据可能不适用于鲑鱼。我们的目的是研究已知对生殖细胞发育至关重要的模型物种基因的空间和组织特异性表达，以鉴定鲑鱼中的生殖细胞特异性因子。基于与其他物种的同源性，在鲑鱼基因组组装中预测了选定的基因。通过PCR测量了各种幼年鲑鱼组织中的基因表达。对于仅在性腺中表达的基因，我们通过qPCR测量了相同组织以及卵、胚胎和幼虫中的表达。最后，我们通过原位杂交（ISH）揭示了性腺特异性mRNA的细胞定位。在鲑鱼基因组中发现几个选定的基因（tdrd7、cxcr4b和dazl）有多个拷贝（基因名称后有数字表示）。tdrd7-2、dazl-2、piwil1和tdrd1的表达仅在幼年鲑鱼的睾丸和卵巢中检测到，tdrd7-2、dazl-2和piwil1的转录本定位于雄性和雌性生殖细胞内。虽然tdrd7-2、piwil1和tdrd1在未受精卵以及所测量的所有胚胎和幼虫阶段都有表达，但dazl-2在未受精卵和胚胎中一直表达到原肠胚形成开始。这项研究表明，已知对生殖细胞发育至关重要的模型物种中的几个基因，在鲑鱼中显示出旁系同源物，与其他物种相比具有不同和相似的表达模式。tdrd7-2、dazl-2、piwil1和tdrd1的转录本仅在幼年性腺中检测到，并存在于卵和随后胚胎的母体RNA中。这些信息对于旨在了解鲑鱼生殖细胞发育的进一步研究具有重要价值。
