Department of Obstetrics and Gynecology, Louisiana State University Health Sciences Center - Shreveport, Louisiana, 71103, USA.
Department of Obstetrics and Gynecology, Louisiana State University Health Sciences Center - Shreveport, Louisiana, 71103, USA; Department of Obstetrics and Gynecology, Second Affiliated Hospital, Harbin Medical University, Harbin, Heilongjiang, 150086, China.
Placenta. 2021 Jan 1;103:43-49. doi: 10.1016/j.placenta.2020.10.016. Epub 2020 Oct 13.
N6-methyladenosine (m6A) has been recognized as one of the most abundant and functionally relevant modifications of RNAs and plays critical roles in biological and pathological processes. Placental trophoblast dysfunction significantly contributes to the pathogenesis of preeclampsia. The present study aimed to determine if altered m6A expression occurs in placental trophoblasts in preeclampsia. Expression of m6A methyltransferase (methyltransferase like 3 (METTL3)), m6A demethylases (fat mass and obesity-associated protein (FTO) and AlkB homolog 5 (ALKBH5)), and m6A reader protein, heterogeneous nuclear ribonucleoprotein C1/C2 (hnRNPC1/C2), were also examined.
A total of 43 placentas (20 normal term, 5 normotensive preterm, and 18 preeclamptic) were used in the study. Expression of m6A, METTL3, FTO, ALKBH5, and hnRNPC1/C2 were examined by immunostaining in villous tissue sections and/or by Western blot of total cellular protein in trophoblasts isolated from normotensive and preeclamptic placentas. Total RNA extracted from trophoblasts was used to measure m6A RNA methylation. Effects of METTL3 on m6A RNA methylation and hnRNPC1/C2 expression were assessed by transfection of METTL3 siRNA in trophoblasts from preeclamptic placentas.
Expression of m6A and m6A RNA methylation were significantly increased in trophoblasts from preeclamptic vs. normotensive placentas, p < 0.05. Expression of METTL3 and hnRNPC1/C2, but not FTO and ALKBH5, was significantly upregulated in trophoblasts from preeclamptic vs. normotensive placentas, p < 0.01. Transfection of METTL3 siRNA significantly reduced the level of m6A RNA methylation and hnRNPC1/C2 expression in trophoblasts from preeclamptic placentas, p < 0.05.
The finding of increased METTL3 expression and m6A RNA methylation associated with increased hnRNPC1/C2 expression provides a new posttranscriptional mechanism that aberrant m6A modification may contribute to trophoblast dysfunction in preeclampsia.
N6-甲基腺嘌呤（m6A）已被认为是 RNA 中最丰富和功能相关的修饰之一，在生物和病理过程中发挥着关键作用。胎盘滋养层功能障碍显著促进子痫前期的发病机制。本研究旨在确定 m6A 表达是否在子痫前期胎盘滋养层中发生改变。还检查了 m6A 甲基转移酶（甲基转移酶样 3（METTL3））、m6A 去甲基化酶（肥胖相关蛋白（FTO）和 AlkB 同源物 5（ALKBH5））和 m6A 读蛋白异质核核糖核蛋白 C1/C2（hnRNPC1/C2）的表达。
本研究共使用 43 个胎盘（20 个正常足月、5 个正常早产和 18 个子痫前期）。通过免疫染色检查绒毛组织切片中 m6A、METTL3、FTO、ALKBH5 和 hnRNPC1/C2 的表达，或通过分离自正常和子痫前期胎盘的滋养层细胞的总细胞蛋白的 Western blot 检查。从滋养层细胞中提取总 RNA，用于测量 m6A RNA 甲基化。通过转染子痫前期胎盘滋养层的 METTL3 siRNA 评估 METTL3 对 m6A RNA 甲基化和 hnRNPC1/C2 表达的影响。
与正常血压胎盘的滋养层相比，子痫前期胎盘的滋养层中 m6A 和 m6A RNA 甲基化表达显著增加，p<0.05。与正常血压胎盘的滋养层相比，子痫前期胎盘的滋养层中 METTL3 和 hnRNPC1/C2 的表达显著上调，而 FTO 和 ALKBH5 的表达则没有显著上调，p<0.01。METTL3 siRNA 的转染显著降低了子痫前期胎盘滋养层的 m6A RNA 甲基化和 hnRNPC1/C2 表达水平，p<0.05。
发现 METTL3 表达增加与 m6A RNA 甲基化增加以及 hnRNPC1/C2 表达增加相关，提供了一种新的转录后机制，即异常的 m6A 修饰可能导致子痫前期的滋养层功能障碍。
