Developmental microRNA expression profiling of murine embryonic orofacial tissue

BACKGROUND: Orofacial development is a multifaceted process involving precise, spatio‐temporal expression of a panoply of genes. MicroRNAs (miRNAs), the largest family of noncoding RNAs involved in gene silencing, represent critical regulators of cell and tissue differentiation. MicroRNA gene expression profiling is an effective means of acquiring novel and valuable information regarding the expression and regulation of genes, under the control of miRNA, involved in mammalian orofacial development. METHODS: To identify differentially expressed miRNAs during mammalian orofacial ontogenesis, miRNA expression profiles from gestation day (GD) ‐12, ‐13 and ‐14 murine orofacial tissue were compared utilizing miRXplore microarrays from Miltenyi Biotech. Quantitative real‐time PCR was utilized for validation of gene expression changes. Cluster analysis of the microarray data was conducted with the clValid R package and the UPGMA clustering method. Functional relationships between selected miRNAs were investigated using Ingenuity Pathway Analysis. RESULTS: Expression of over 26% of the 588 murine miRNA genes examined was detected in murine orofacial tissues from GD‐12–GD‐14. Among these expressed genes, several clusters were seen to be developmentally regulated. Differential expression of miRNAs within such clusters wereshown to target genes encoding proteins involved in cell proliferation, cell adhesion, differentiation, apoptosis and epithelial‐mesenchymal transformation, all processes critical for normal orofacial development. CONCLUSIONS: Using miRNA microarray technology, unique gene expression signatures of hundreds of miRNAs in embryonic orofacial tissue were defined. Gene targeting and functional analysis revealed that the expression of numerous protein‐encoding genes, crucial to normal orofacial ontogeny, may be regulated by specific miRNAs. Birth Defects Research (Part A), 2010. © 2010 Wiley‐Liss, Inc.     

Systematic analysis of genomic organization and heterogeneities of miRNA cluster in vertebrates

The clustering propensity of microRNA genes is a common biological phenomenon in various animal and plant species. To gain novel insight into genomic organization and potential functional heterogeneities of miRNA clusters in vertebrates from a genome scale, we used large scale data and presented a comprehensive analysis to examine various features of genomic organization of miRNA clusters across seven vertebrates by a combination of comparative genomics and bioinformatics approaches. The results of pair-wise distance analysis of same-strand consecutive miRNAs suggested that the fractions of the miRNA gene pairs are higher at relatively short pair-wise distances than those of protein-coding genes and other non-coding RNA genes. Especially relatively small number of miRNAs is more clustered at very short pair-wise distances than expected at random. We further observed significant difference between real miRNA clusters and randomly organized clusters for different aspects, including higher overlap of target genes, fewer seed types and significant enrichment in diseases. However, the extent of these features of clustered miRNAs has a different tendency and largely depends on inter-miRNA distances because of diverse clustering propensity of miRNAs in vertebrates, suggesting that this cooperated function or cooperative effects between miRNAs in clusters perhaps be affected by inter-miRNA distances.     

MicroRNA profile analysis on duck feather follicle and skin with high-throughput sequencing technology

Skin acts an important protection role in animal survival and it evolves with the animal divergence. We identified the conserved miRNA families of skin among duck and other species. Cluster analysis showed that the species with similar skin characteristics were clustered into the same group, indicating miRNAs are important in skin function and skin evolution. The miRNA profiles demonstrated that different miRNA regulation mechanism may exist in contour feather follicles (with the surrounding skin) and down feather follicles (with the surrounding skin). Comparing the highly abundant miRNAs with those of mammalian hair follicles and skins, different miRNAs and miRNA families were found, suggesting the different ways in feather follicles and mammalian hair follicles. Bioinformatics prediction indicated that seven miRNAs probably targeted the genes of Wnt/β-catenin, Shh/BMP and Notch pathways which were important in feather morphogenesis. Further analysis should be conducted to experimentally validate the relationships between miRNAs and their predicted target genes because the target genes were based exclusively upon the bioinformatics.     

miRNA对水稻生长发育的调控

MicroRNA(miRNA)是一类小的非编码RNA,它们主要在转录后水平对靶mRNA进行切割或抑制mRNA的翻译来调控基因的表达. miRNA通过对靶基因的调控参与植物的生长发育、胁迫应答和代谢过程.在水稻中,已经发现并初步验证了许多与生长发育相关的miRNA,它们对水稻不同器官和形态发育发挥着重要作用.本文综述了水稻miRNA的发生和调控机制、靶基因的预测,重点介绍了miRNA对水稻生长发育和形态建成的研究进展,并对研究过程中存在的问题进行了讨论.为更好地了解miRNA及其靶基因在提高水稻产量和品质方面的作用,进一步解析miRNA在水稻中的调控机制提供参考.     

Clustering and conservation patterns of human microRNAs

MicroRNAs (miRNAs) are ~22 nt-long non-coding RNA molecules, believed to play important roles in gene regulation. We present a comprehensive analysis of the conservation and clustering patterns of known miRNAs in human. We show that human miRNA gene clustering is significantly higher than expected at random. A total of 37% of the known human miRNA genes analyzed in this study appear in clusters of two or more with pairwise chromosomal distances of at most 3000 nt. Comparison of the miRNA sequences with their homologs in four other organisms reveals a typical conservation pattern, persistent throughout the clusters. Furthermore, we show enrichment in the typical conservation patterns and other miRNA-like properties in the vicinity of known miRNA genes, compared with random genomic regions. This may imply that additional, yet unknown, miRNAs reside in these regions, consistent with the current recognition that there are overlooked miRNAs. Indeed, by comparing our predictions with cloning results and with identified miRNA genes in other mammals, we corroborate the predictions of 18 additional human miRNA genes in the vicinity of the previously known ones. Our study raises the proportion of clustered human miRNAs that are <3000 nt apart to 42%. This suggests that the clustering of miRNA genes is higher than currently acknowledged, alluding to its evolutionary and functional implications.     

玉米microRNAs及其靶基因的生物信息学预测

microRNAs (miRNAs) 是一类非编码的小分子RNA, 通过碱基互补调控靶基因的表达。鉴定和发现新的miRNAs及其靶基因, 对揭示miRNAs在基因表达调控中的作用至关重要。玉米全基因组测序工作开展较晚, 已经鉴定登记的miRNAs很少, 对靶基因的调控作用尚待解明。文章根据miRNA进化上的保守性, 以已知的植物miRNAs为探针, 与相关数据库中玉米表达序列标签(EST)和基因组序列(GSS)中的非编码序列比对, 共发现11个新的miRNA前体。虽然在序列长度和二级结构方面各有变化, 但这11个前体均可折叠形成miRNA家族的标准二级结构。通过靶基因预测, 找到其中7条miRNAs的26个靶基因, 分别编码与新陈代谢、信号转导、转录调节、跨膜运输、生物和非生物胁迫及叶绿体组装等相关的蛋白。这些miRNAs及其靶基因的鉴定, 补充了miRNA数据库的不足。