Nomura Jumpei, Yokoi Hayato, Hondo Eiichi, Iida Atsuo
Laboratory of Animal Morphology, Graduate School of Bioagricultural Sciences, Nagoya University, Tokai National Higher Education and Research System, Nagoya, Aichi, Japan.
Laboratory of Fish Genetics, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi, Japan.
Biochem Biophys Res Commun. 2023 Feb 12;644:79-84. doi: 10.1016/j.bbrc.2023.01.009. Epub 2023 Jan 5.
In the viviparous teleost species belonging to the family Goodeidae, intraovarian embryos absorb maternal supplements while they grow during the gestation period. They take up the components via trophotaeniae, a hindgut-derived placental structure. Our previous study using a goodeid species Xenotoca eiseni revealed that intraovarian embryos absorb the yolk protein vitellogenin (Vtg) via the trophotaenia. However, another group indicated yolk components accumulate in the intestinal lumen of X. eiseni embryos. Here, we investigated whether the intestinal duct is capable of protein uptake, as is the trophotaenia. Immunohistochemical studies indicated that endogenous vitellogenin is detected in the intestinal epithelial cells of the intraovarian embryo. Tracer analysis using FITC-Vtg also indicated that intestinal tissues can take up protein. The endocytosis-related genes expressed in trophotaenia were also detected in the intestinal tissues of the embryo. Lipid transporter genes which are not expressed in the trophotaenia were detected in the embryonic intestine. This evidence suggests that the intraovarian embryo of X. eiseni possesses two distinct sites for uptake of the maternal proteins. However, the presumed functions of the embryonic intestine and trophotaenia might be not identical. The study provides a new perspective on how mother-to-embryo matrotrophic interactions have changed in the evolution of viviparous teleosts.
在属于古氏鱼科的胎生硬骨鱼物种中，卵巢内的胚胎在妊娠期生长过程中会吸收母体的营养物质。它们通过滋养带吸收这些成分，滋养带是一种源自后肠的胎盘结构。我们之前使用古氏鱼物种艾氏异齿鳉进行的研究表明，卵巢内的胚胎通过滋养带吸收卵黄蛋白卵黄生成素（Vtg）。然而，另一组研究表明，卵黄成分在艾氏异齿鳉胚胎的肠腔内积累。在这里，我们研究了肠道导管是否像滋养带一样能够摄取蛋白质。免疫组织化学研究表明，在卵巢内胚胎的肠上皮细胞中检测到内源性卵黄生成素。使用异硫氰酸荧光素标记的卵黄生成素（FITC-Vtg）进行的示踪分析也表明，肠道组织能够摄取蛋白质。在滋养带中表达的内吞作用相关基因在胚胎的肠道组织中也被检测到。在胚胎肠道中检测到了在滋养带中不表达的脂质转运蛋白基因。这一证据表明，艾氏异齿鳉的卵巢内胚胎拥有两个不同的母体蛋白质摄取位点。然而，胚胎肠道和滋养带的推测功能可能并不相同。这项研究为胎生硬骨鱼进化过程中母胎营养相互作用的变化提供了新的视角。
