Department of Animal Sciences and DH Barron Reproductive and Perinatal Biology Research Program, University of Florida, Gainesville, FL 32611-0910, USA.
Mol Cell Endocrinol. 2011 Jan 30;332(1-2):170-9. doi: 10.1016/j.mce.2010.10.009. Epub 2010 Oct 19.
Insulin-like growth factor 1 (IGF1) is an important endocrine signal for regulation of early embryonic development. It increases the proportion of preimplantation embryos becoming blastocysts, alters blastocyst gene expression, improves resistance of embryos to various stresses and can enhance survival of embryos after transfer to recipients. The present study had two objectives. The first was to determine whether the thermoprotective actions of IGF1 on the preimplantation bovine embryo was developmentally regulated, with the two-cell embryo being refractory to IGF1. The second was to determine the molecular basis for the improved competence of embryos treated with IGF1 to establish pregnancy after transfer to heat-stressed recipients. Treatment of embryos with 100 ng/ml IGF1 reduced the effects of heat shock on embryos ≥16 cells at day 5 after insemination but did not provide thermoprotection to two-cell embryos. Failure of IGF1 to alter embryo survival after heat shock was not associated with reduced expression of genes involved in IGF1 signaling (IGF1R, RAF1, PI3K, and MAPK) or immunoreactive IGF1R protein. Treatment with IGF1 had little effect on the transcriptome at the blastocyst stage of development, with a total of 102 differentially expressed genes identified. Among the differentially expressed genes were several involved in apoptosis, protection against free radicals and development. Changes in gene expression were consistent with IGF1 acting to induce an anti-apoptotic state and inhibit neurulation. In conclusion, thermoprotective actions of IGF1 are developmentally regulated. Failure of IGF1 to protect the two-cell embryo from heat shock could reflect the fact that these embryos are maximally sensitive to damage caused by heat shock or reflect the quiescence of the embryonic genome at this stage of development. Changes in gene expression at the blastocyst stage induced by IGF1 could contribute to the increased survival of IGF1-treated embryos when transferred during periods of heat stress.
胰岛素样生长因子 1（IGF1）是调节早期胚胎发育的重要内分泌信号。它增加了胚胎成为囊胚的比例，改变了囊胚的基因表达，提高了胚胎对各种应激的抵抗力，并能提高胚胎在转移到受体后的存活率。本研究有两个目的。第一个目的是确定 IGF1 对牛胚胎的热保护作用是否受发育调控，两细胞胚胎对 IGF1 有抗性。第二个目的是确定 IGF1 处理的胚胎在转移到热应激受体后建立妊娠的能力提高的分子基础。用 100ng/ml IGF1 处理胚胎可降低胚胎在受精后第 5 天 ≥16 细胞时的热休克作用，但不能为两细胞胚胎提供热保护。IGF1 不能改变热休克后胚胎的存活率与参与 IGF1 信号转导的基因（IGF1R、RAF1、PI3K 和 MAPK）或免疫反应性 IGF1R 蛋白的表达减少无关。IGF1 处理对囊胚发育阶段的转录组几乎没有影响，总共鉴定出 102 个差异表达基因。在差异表达的基因中，有几个与凋亡、自由基保护和发育有关。基因表达的变化与 IGF1 诱导抗凋亡状态和抑制神经形成一致。总之，IGF1 的热保护作用是受发育调控的。IGF1 不能保护两细胞胚胎免受热休克的影响，可能反映了这些胚胎对热休克引起的损伤最敏感，或者反映了胚胎基因组在这一发育阶段的静止状态。IGF1 诱导的囊胚阶段基因表达的变化可能有助于增加 IGF1 处理的胚胎在热应激期间转移时的存活率。
