Early embryos are vulnerable to environmental insults, such as medications taken by the mother. Due to increasing prevalence of hypercholesterolemia, more women of childbearing potential are taking cholesterol-lowering medications called statins. Previously, we showed that inhibition of the mevalonate pathway by statins impaired mouse preimplantation development, by modulating HIPPO signaling, a key regulator for trophectoderm (TE) lineage specification. Here, we further evaluated molecular events that are altered by mevalonate pathway inhibition during the timeframe of morphogenesis and cell lineage specification. Whole transcriptome analysis revealed that statin treatment dysregulated gene expression underlying multiple processes, including cholesterol biosynthesis, HIPPO signaling, cell lineage specification and endoplasmic reticulum (ER) stress response. We explored mechanisms that link the mevalonate pathway to ER stress, because of its potential impact on embryonic health and development. Upregulation of ER stress-responsive genes was inhibited when statin-treated embryos were supplemented with the mevalonate pathway product, geranylgeranyl pyrophosphate (GGPP). Inhibition of geranylgeranylation was sufficient to upregulate ER stress-responsive genes. However, ER stress-responsive genes were not upregulated by inhibition of ras homolog family member A (RHOA), a geranylgeranylation target, although it interfered with TE specification and blastocyst cavity formation. In contrast, inhibition of Rac family small GTPase 1 (RAC1), another geranylgeranylation target, upregulated ER stress-responsive genes, while it did not impair TE specification or cavity formation. Thus, our study suggests that the mevalonate pathway regulates cellular homeostasis (ER stress repression) and differentiation (TE lineage specification) in preimplantation embryos through GGPP-dependent activation of two distinct small GTPases, RAC1 and RHOA, respectively. Translation of the findings to human embryos and clinical settings requires further investigations.

中文翻译：

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甲羟戊酸通路对小鼠植入前胚胎内质网应激和滋养外胚层谱系规范的调控

早期胚胎容易受到环境损害，例如母亲服用的药物。由于高胆固醇血症的患病率越来越高，越来越多的育龄妇女正在服用称为他汀类药物的降胆固醇药物。以前，我们通过调节 HIPPO 信号传导（滋养外胚层 (TE) 谱系规范的关键调节因子）表明，他汀类药物对甲羟戊酸途径的抑制会损害小鼠植入前发育。在这里，我们进一步评估了在形态发生和细胞谱系规范的时间范围内由甲羟戊酸途径抑制改变的分子事件。全转录组分析显示，他汀类药物治疗导致多个过程的基因表达失调，包括胆固醇生物合成、HIPPO 信号传导、细胞谱系规范和内质网（ER）应激反应。我们探索了将甲羟戊酸途径与 ER 应激联系起来的机制，因为它对胚胎健康和发育有潜在影响。当他汀类药物处理的胚胎补充甲羟戊酸途径产物香叶基香叶基焦磷酸 (GGPP) 时，ER 应激反应基因的上调受到抑制。香叶基香叶酰化的抑制足以上调 ER 应激反应基因。然而，ER 应激反应基因并未通过抑制 ras 同源家族成员 A (RHOA)（一种香叶基香叶酰化靶标）而上调，尽管它干扰了 TE 规范和胚泡腔的形成。相比之下，抑制 Rac 家族小 GTPase 1 (RAC1)，另一种香叶基香叶酰化靶标，上调 ER 应激反应基因，而它不会影响 TE 规格或空腔形成。因此，我们的研究表明，甲羟戊酸途径分别通过 GGPP 依赖性激活两种不同的小 GTP 酶 RAC1 和 RHOA 来调节植入前胚胎中的细胞稳态（ER 应激抑制）和分化（TE 谱系规范）。将研究结果转化为人类胚胎和临床环境需要进一步调查。