Nutrients are utilized and re-constructed by endodermal epithelial cells (EECs) of yolk sac membrane (YSM) in avian species during embryonic development. Sterol O-acyltransferase 1 (SOAT1) is the key enzyme to convert cholesterol to cholesteryl ester for delivery to growing embryos. During embryonic development, yolk absorption is concomitant with significant changes of SOAT1 mRNA concentration and enzyme activity in YSM. Presence of microRNAs (miRNAs) are observed in the embryonic liver and muscle during avian embryogenesis. However, the expression of miRNAs in YSM during embryogenesis and the involvement of miRNAs in lipid utilization are not known. Using a miRNA sequencing technique, we found several miRNA candidates and confirmed their expression patterns individually by real time PCR. MiRNA candidates were selected based on the expression pattern and their possible roles in inhibiting transforming growth factor beta receptor type 1 (TGFBR1) that would regulate the function of SOAT1. Similar to SOAT1 mRNA, the gga-miR-181a-5p expression was gradually elevated during embryonic development. However, the expression of gga-miR-429-3p in YSM was gradually decreased during embryonic development. The inhibitory effects of gga-miR-181a-5p or gga-miR-429-3p on the potential targets (SOAT1 and TGFBR1) were demonstrated by transient miRNA transfections in EECs. We also found that mutated TGFBR1 3'UTR prevented the direct pairings of gga-miR-181a-5p and gga-miR-429-3p. Treatment of TGFBR1 inhibitor, LY364947, further decreased SOAT1 transcription. Similar results were also observed by the miRNA transfection studies. The results showed the vital participations of gga-miR-181a-5p and gga-miR-429-3p in regulating TGFβ pathway, and affecting downstream SOAT1 expression and function in the YSM. This is indicative of possible regulation of avian yolk lipid utilization by changing YSM miRNA expressions.

中文翻译：

---

在日本鹌鹑的内胚层上皮细胞中，gga-miR-181a-5p和gga-miR-429-3p通过TGFβ途径抑制了Sterol-O酰基转移酶1。

在禽类胚胎发育过程中，卵黄囊膜（YSM）的内胚层上皮细胞（EEC）利用并重建了营养物质。甾醇O-酰基转移酶1（SOAT1）是将胆固醇转化为胆固醇酯以递送至正在生长的胚胎的关键酶。在胚胎发育过程中，蛋黄吸收伴随着YSM中SOAT1 mRNA浓度和酶活性的显着变化。在禽类胚胎发生过程中，在胚胎肝和肌肉中观察到了microRNA（miRNA）的存在。然而，尚不清楚胚胎发生过程中YSM中miRNA的表达以及miRNA在脂质利用中的参与。使用miRNA测序技术，我们发现了几种miRNA候选物，并通过实时PCR分别确认了它们的表达模式。根据表达模式及其在抑制可调节SOAT1功能的转化生长因子β受体1型（TGFBR1）中的可能作用来选择MiRNA候选物。与SOAT1 mRNA相似，在胚胎发育过程中，gga-miR-181a-5p表达逐渐升高。然而，在胚胎发育过程中，YSM中gga-miR-429-3p的表达逐渐降低。通过在EEC中进行瞬时miRNA转染，证明了gga-miR-181a-5p或gga-miR-429-3p对潜在靶标（SOAT1和TGFBR1）的抑制作用。我们还发现，突变的TGFBR1 3'UTR阻止了gga-miR-181a-5p和gga-miR-429-3p的直接配对。TGFBR1抑制剂LY364947的处理进一步降低了SOAT1转录。miRNA转染研究也观察到了相似的结果。结果表明，gga-miR-181a-5p和gga-miR-429-3p参与了TGFβ途径的调控，并影响YSM下游SOAT1的表达和功能。这表明可能通过改变YSM miRNA表达来调节禽蛋黄脂质利用。