Laboratory of Animal Morphology, Graduate School of Bioagricultural Sciences, Nagoya University, Tokai National Higher Education and Research System, Nagoya, Aichi, Japan.
Laboratory of Animal Morphology, Graduate School of Bioagricultural Sciences, Nagoya University, Tokai National Higher Education and Research System, Nagoya, Aichi, Japan.
Biochim Biophys Acta Mol Cell Biol Lipids. 2022 Sep;1867(9):159183. doi: 10.1016/j.bbalip.2022.159183. Epub 2022 Jun 2.
Certain viviparous animals possess mechanisms for mother-to-embryo nutrient transport during gestation. Xenotoca eiseni is one such viviparous teleost species in which the mother supplies proteins and other components to the offspring developing in the ovary. The embryo possesses trophotaenia, hindgut-derived placental structure, to receive the maternal supplement. However, research on the molecular mechanisms underlying viviparous species is scarce in non-mammalian vertebrates, including teleosts. Thus, we conducted this study to investigate the mechanism for nutrient absorption and degradation in trophotaeniae of X. eiseni. A tracer assay indicated that a lipid transfer protein, vitellogenin (Vtg), was absorbed into the epithelial layer cells of the trophotaeniae. Vtg uptake was significantly suppressed by Pitstop-2, an inhibitor of clathrin-mediated endocytosis. Gene expression analysis indicated that the genes involved in endocytosis-mediated lipolysis and lysosomal cholesterol transport were expressed in the trophotaeniae. In contrast, plasma membrane transporters expressed in the intestinal tract were not functional in the trophotaeniae. Our results suggested that endocytosis-mediated lysosomal lipolysis is one of the mechanisms underlying maternal component metabolism. Thus, our study demonstrated how viviparous teleost species have acquired a unique developmental system that is based on the hindgut-derived placenta.
某些胎生动物在妊娠期间具有母体向胚胎输送营养物质的机制。 Xenotoca eiseni 就是这样一种胎生硬骨鱼物种，其母体将蛋白质和其他成分输送给在卵巢中发育的后代。胚胎具有滋养层，即由后肠衍生而来的胎盘结构，以接收母体的补充。然而，在非哺乳动物的脊椎动物中，包括硬骨鱼，对胎生物种的分子机制的研究还很匮乏。因此，我们进行了这项研究，以探讨 Xenotoca eiseni 中滋养层的营养吸收和降解机制。示踪剂分析表明，一种脂质转移蛋白，卵黄蛋白原（Vtg），被吸收到滋养层的上皮层细胞中。Vtg 的摄取被 clathrin 介导的内吞作用抑制剂 Pitstop-2 显著抑制。基因表达分析表明，参与内吞介导的脂解和溶酶体胆固醇转运的基因在滋养层中表达。相比之下，在肠道中表达的质膜转运体在滋养层中不起作用。我们的结果表明，内吞介导的溶酶体脂解是母体成分代谢的机制之一。因此，我们的研究表明了胎生硬骨鱼物种如何获得了一种基于后肠衍生胎盘的独特发育系统。
