The molecular basis of viviparity in non-mammalian species has not been widely studied. Neoditrema ransonnetii, a surfperch, is a matrotrophic teleost whose fetuses grow by ovarian cavity fluid (OCF) ingestion and by nutrient absorption via their enlarged hindgut. We performed a proteomics analysis of N. ransonnetii plasma protein and found proteins specific to pregnant females; one of these was identified as transthyretin (TTR), a thyroid hormone distributor protein. We synthesized recombinant protein rNrTTR and raised an antibody, anti-rNrTTR, against it. Semi-quantitative analysis by western blotting using the antibody demonstrated that plasma TTR levels were significantly greater in pregnant fish than in non-pregnant fish. OCF and fetal plasma also contained high TTR levels. Immunohistochemical staining showed that large amounts of maternal TTR were taken up by fetal intestinal epithelial cells. These results indicate that maternal TTR is secreted into OCF and taken up by fetal enterocytes, presumably to deliver thyroid hormones to developing fetuses.

中文翻译：

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母体转甲状腺素蛋白在胎生硬骨鱼 Neoditrema ransonnetii (Perciformes, Embiotocidae) 中向胎儿的转运

非哺乳动物物种胎生的分子基础尚未得到广泛研究。Neoditrema ransonnetii，一种冲浪鲈，是一种营养性硬骨鱼，其胎儿通过摄入卵巢腔液 (OCF) 和通过增大的后肠吸收营养来生长。我们对 N.ransonnetii 血浆蛋白进行了蛋白质组学分析，发现了妊娠女性特有的蛋白质；其中一个被鉴定为甲状腺素转运蛋白 (TTR)，一种甲状腺激素分配蛋白。我们合成了重组蛋白 rNrTTR 并针对它产生了抗 rNrTTR 抗体。使用抗体通过蛋白质印迹进行的半定量分析表明，怀孕鱼的血浆 TTR 水平显着高于非怀孕鱼。OCF 和胎儿血浆也含有高 TTR 水平。免疫组化染色显示大量母体TTR被胎儿肠上皮细胞吸收。这些结果表明，母体 TTR 被分泌到 OCF 中并被胎儿肠细胞吸收，可能是为了向发育中的胎儿输送甲状腺激素。