DNA synthesis and methylations are crucial during pre-implantation embryonic development, and are mediated by one-carbon metabolism of folates. Folates, transported into the cells via folate receptors (FOLR1 and FOLR2) and carriers (SLC19A1), are metabolized by various enzymes involved in folate-methionine cycle. However, the variations in temporal expression of folate transporters and folate-methionine cycle enzymes during pre-implantation embryo development is obscure. Thus, the present study aimed to investigate the differential expression of the genes for folate transporters and folate-methionine cycle enzymes. We also examined the expression of folate transport proteins in different pre-implantation development stages. Immature buffalo oocytes were matured in maturation medium followed by in vitro fertilization and culture at standard culture conditions. The temporal pattern of gene expression in buffalo, when compared to previous studies, indicated an inter-specific variation. The transcripts of some enzymes and folate transporters were significantly upregulated after zygotic genome activation. The transcripts as well as proteins for FOLR1, FOLR2 and SLC19A1 were present in oocytes and all the pre-implantation embryo stages. FOLR1 was present in the nuclei of different stages of developing embryos but not in the metaphase (MII) oocytes. As a result, the present study advocates the existence of active folate transport in buffalo oocytes and pre-implantation embryos. The data provided by the analysis of differential gene expression of folate transporters and metabolic enzymes would likely contribute to a better understanding of the role of folates in embryo development as well as advancements in assisted reproductive technologies.

DNA 合成和甲基化在植入前胚胎发育过程中至关重要，并且由叶酸的单碳代谢介导。叶酸通过叶酸受体（FOLR1 和 FOLR2）和载体（SLC19A1）转运到细胞中，被参与叶酸-甲硫氨酸循环的各种酶代谢。然而，叶酸转运蛋白和叶酸甲硫氨酸循环酶在植入前胚胎发育过程中的时间表达变化尚不清楚。因此，本研究旨在研究叶酸转运蛋白和叶酸-甲硫氨酸循环酶基因的差异表达。我们还检查了叶酸转运蛋白在不同植入前发育阶段的表达。未成熟的水牛卵母细胞在成熟培养基中成熟，然后在标准培养条件下进行体外受精和培养。与以前的研究相比，水牛基因表达的时间模式表明存在种间变异。一些酶和叶酸转运蛋白的转录物在合子基因组激活后显着上调。FOLR1、FOLR2 和 SLC19A1 的转录本和蛋白质存在于卵母细胞和所有植入前胚胎阶段。FOLR1 存在于胚胎发育不同阶段的细胞核中，但不存在于中期 (MII) 卵母细胞中。因此，本研究提倡在水牛卵母细胞和植入前胚胎中存在主动叶酸转运。