Mommens Maren, Fernandes Jorge Mo, Bizuayehu Teshome T, Bolla Sylvie L, Johnston Ian A, Babiak Igor
Faculty of Biosciences and Aquaculture, Bodø University College, N-8049 Bodø, Norway.
BMC Res Notes. 2010 May 24;3:138. doi: 10.1186/1756-0500-3-138.
The commercial production of Atlantic halibut (Hippoglossus hippoglossus L.) suffers from a major bottleneck due to the low success of producing juveniles for on-growing. Atlantic halibut females are routinely hand-stripped and incorrect timing of stripping can result in low quality eggs due to post-ovulatory aging. Post-ovulatory aging leads to compositional changes in eggs that include maternally provided proteins and RNAs. There have been few studies of the maternally provided mRNA transcripts that control early development in commercially important fish species. The present study aimed to study maternal gene expression in Atlantic halibut and its relation to egg quality parameters including blastomere symmetry and hatching success.
A maternal EST library containing 2341 sequences was constructed by suppressive subtractive hybridisation. Thirty genes were selected for expression studies; 23 novel genes and 7 genes with documented roles in early development. The expressions of twenty-one selected genes were measured by qPCR from fertilization to the 10-somite stage. Three genes were identified as strictly maternal genes that were expressed until the start of gastrulation; askopos (kop), si:dkey-30j22.9 (Tudor family member), and Tudor 5 protein (Tdrd5). The expressions of 18 genes at the 8-cell stage were correlated with egg quality parameters. The majority of genes showed either no or very minor correlations with egg quality parameter. However, two genes correlated positively with hatching success (r> 0.50, HHC00353: r = 0.58, p < 0.01; HHC01517: r = 0.56, p < 0.01) and one gene (HHC00255) was negatively correlated with the percentage of normal blastomeres (r = -0.62, p < 0.05).
During this study we have related maternal levels of gene expression to hatching success in fish. Poor hatching success was not correlated with a general decrease in transcript abundance but with low transcript levels of some specific genes. Thus, the molecular mechanisms leading to low Atlantic halibut egg quality cannot be entirely explained by post-ovulatory aging.
大西洋庸鲽（Hippoglossus hippoglossus L.）的商业化生产面临一个主要瓶颈，即培育幼鱼的成功率较低，无法满足后续养殖需求。大西洋庸鲽雌鱼通常采用人工挤卵的方式获取鱼卵，然而，挤卵时间不当会因排卵后卵子老化而导致鱼卵质量下降。排卵后卵子老化会引发卵子成分变化，包括母源提供的蛋白质和RNA。目前，针对商业重要鱼类中控制早期发育的母源mRNA转录本的研究较少。本研究旨在探究大西洋庸鲽的母源基因表达及其与卵质量参数（包括卵裂球对称性和孵化成功率）的关系。
通过抑制性消减杂交构建了一个包含2341个序列的母源EST文库。选择了30个基因进行表达研究，其中包括23个新基因和7个在早期发育中具有明确作用的基因。通过qPCR测定了从受精到10体节期21个选定基因的表达。鉴定出3个严格的母源基因，它们在原肠胚形成开始前一直表达，分别是askopos（kop）、si:dkey-30j22.9（都铎家族成员）和都铎5蛋白（Tdrd5）。8细胞期18个基因的表达与卵质量参数相关。大多数基因与卵质量参数无相关性或相关性很小。然而，有两个基因与孵化成功率呈正相关（r>0.50，HHC00353：r = 0.58，p < 0.01；HHC01517：r = 0.56，p < 0.01），一个基因（HHC00255）与正常卵裂球的百分比呈负相关（r = -0.62，p < 0.05）。
在本研究中，我们将鱼类的母源基因表达水平与孵化成功率联系起来。孵化成功率低并非与转录本丰度的普遍降低相关，而是与某些特定基因的低转录水平相关。因此，导致大西洋庸鲽卵质量低的分子机制不能完全用排卵后卵子老化来解释。
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