Molecular Medicine Branch, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA.
J Transl Med. 2009 Nov 25;7:98. doi: 10.1186/1479-5876-7-98.
MicroRNAs are approximately 22nt-long small non-coding RNAs that negatively regulate protein expression through mRNA degradation or translational repression in eukaryotic cells. Based upon their importance in regulating development and terminal differentiation in model systems, erythrocyte microRNA profiles were examined at birth and in adults to determine if changes in their abundance coincide with the developmental phenomenon of hemoglobin switching.
Expression profiling of microRNA was performed using total RNA from four adult peripheral blood samples compared to four cord blood samples after depletion of plasma, platelets, and nucleated cells. Labeled RNAs were hybridized to custom spotted arrays containing 474 human microRNA species (miRBase release 9.1). Total RNA from Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines provided a hybridization reference for all samples to generate microRNA abundance profile for each sample.
Among 206 detected miRNAs, 79% of the microRNAs were present at equivalent levels in both cord and adult cells. By comparison, 37 microRNAs were up-regulated and 4 microRNAs were down-regulated in adult erythroid cells (fold change > 2; p < 0.01). Among the up-regulated subset, the let-7 miRNA family consistently demonstrated increased abundance in the adult samples by array-based analyses that were confirmed by quantitative PCR (4.5 to 18.4 fold increases in 6 of 8 let-7 miRNA). Profiling studies of messenger RNA (mRNA) in these cells additionally demonstrated down-regulation of ten let-7 target genes in the adult cells.
These data suggest that a consistent pattern of up-regulation among let-7 miRNA in circulating erythroid cells occurs in association with hemoglobin switching during the fetal-to-adult developmental transition in humans.
microRNAs 是大约 22nt 长的小非编码 RNA，通过 mRNA 降解或翻译抑制在真核细胞中负调控蛋白质表达。基于它们在调节模型系统中的发育和终末分化的重要性，检查了出生时和成人的红细胞 microRNA 谱，以确定它们丰度的变化是否与血红蛋白转换的发育现象一致。
使用来自四个成人外周血样本和四个脐带血样本的总 RNA，在去除血浆、血小板和有核细胞后，进行 microRNA 表达谱分析。标记的 RNA 与含有 474 种人类 microRNA 种类（miRBase release 9.1）的定制点样阵列杂交。EBV 转化的淋巴母细胞系的总 RNA 为所有样品提供了杂交参考，以生成每个样品的 microRNA 丰度谱。
在 206 个检测到的 miRNAs 中，79%的 microRNAs 在脐带和成人细胞中的水平相当。相比之下，37 个 microRNAs 在成人红细胞中上调，4 个 microRNAs下调（倍数变化>2；p<0.01）。在上调的 microRNA 中，let-7 miRNA 家族在成人样本中的丰度通过基于阵列的分析一致增加，这通过定量 PCR 得到证实（在 8 个 let-7 miRNA 中有 6 个的倍数增加 4.5 到 18.4 倍）。这些细胞中的信使 RNA（mRNA）分析还表明，在成人细胞中，10 个 let-7 靶基因下调。
这些数据表明，在人类胎儿到成人发育过渡期间，循环红细胞中 let-7 miRNA 的一致上调模式与血红蛋白转换有关。
