Characterization and expression of lin-28a involved in lin28/let-7signal pathway during early development of P. olivaceus

PM2.5 induces the distant metastasis of lung adenocarcinoma via promoting the stem cell properties of cancer cells

Lung cancer is the most common cancer in China and second worldwide, of which the incidence of lung adenocarcinoma is rising. As an independent factor, air pollution has drawn the attention of the public. An increasing body of studies has focused on the effect of PM_2.5 on lung adenocarcinoma; however, the mechanism remains unclear. We collected the PM_2.5 in two megacities, Beijing (BPM) and Shijiazhuang (SPM), located in the capital of China, and compared the different components and sources of PM_2.5 in the two cities. Vehicle emissions are the primary sources of BPM, whereas SPM is industrial emissions. We found that chronic exposure to PM_2.5 promotes the tumorigenesis and metastasis of lung adenocarcinoma in patient-derived xenograft (PDX) models, as well as the migration and invasion of lung adenocarcinoma cell lines. SPM has more severe effects in vivo and in vitro. The underlying mechanisms are related to the stem cell properties of cancer cells, the epithelial-mesenchymal transition (EMT) process, and the corresponding miRNAs. It is hopeful to provide a theoretical basis for improving air pollution in China, especially in the capital area, and is of the significance of long-term survival of lung cancer patients.

Distinct expression patterns of seven crucial microRNAs during early embryonic development in medaka (Oryzias latipes)

MicroRNAs (i.e. miRNAs) are small non-coding RNAs that play essential modulation roles in embryonic development in vertebrates. Paternal and maternal miRNAs contribute to the development of post-fertilization embryo and zygotic genome activation. The pattern of expression and their roles in embryonic development of medaka are not clearly understood. The present study, therefore, examined a temporal expression of seven miRNAs, ola-let-7a, ola-miR-202-3p, ola-miR-126-3p, ola-miR-122, ola-miR-92a, ola-miR-125a-3p and ola-miR-430a in sperm, oocytes, and embryos during early developmental stages. Three unique expression patterns of miRNAs were observed. ola-let7a, ola-miR-202-3p and ola-miR-126-3p showed both paternal and maternal expression, and ola-miR-122, ola-miR-92a, ola-miR-125a-3p showed maternal expression only. The expression of six out of seven miRNAs significantly decreased after maternal-zygotic transition (MZT), whereas ola-miR-430a expression initiated only after MZT. The temporal dynamic expression of these miRNAs suggests their potential roles in early embryogenesis and genome-zygotic activation in medaka.

Comparative expression analysis of let-7 microRNAs during ovary development in Megalobrama amblycephala

As a critical regulator of gene expression, let-7 family miRNAs have been reported to be involved in multiple physiological processes. In this study, in order to elucidate the putative regulatory effect of let-7 miRNAs during fish gonadal development and to identify which member is crucial for this regulation, the expression of ten members including let-7a/b/c/d/e/f/g/h/i/j were quantified in ovary, pituitary, and brain tissues during the different ovarian developmental stages of blunt snout bream Megalobrama amblycephala. According to the data from analysis of expression patterns, let-7a showed the highest expression value in almost all the tested ovaries, pituitaries, and brains, with let-7b and let-7d moderately expressed, following by other let-7 miRNAs. In terms of the differential expression levels of ten let-7 miRNAs at each developmental stage, the results showed that let-7a/b/d/f/h expression gradually increased during the ovary development from stage I to V and dropped significantly at the phase VI in ovary tissues. However, the expression of let-7a/b/e/f in pituitary increased during the ovary development from stage I to IV and declined at stage V. Among all the let-7 miRNAs, let-7a/b/d had the highest expression and their expression patterns were consistent with the gonad development of M. amblycephala. Furthermore, the mostly predicted target genes of let-7 miRNAs are significantly enriched in signaling pathways closely related to gonadal development through KEGG enrichment analysis. These results indicate that let-7 miRNA members, especially let-7a/b/d, may play important roles in the regulation of ovary development in M. amblycephala through negatively regulating expression of their target genes.

Lin28 promotes dental pulp cell proliferation via upregulation of cyclin-dependent proteins and interaction with let-7a/IGF2BP2 pathways

Caries, pulpitis, and trauma are the main causes of dental pulp damage. The regeneration capacity of dental pulp declines with age. Lin28 is a conserved RNA-binding protein in higher eukaryotes that regulates several important cellular functions associated with development, glucose metabolism, differentiation, and pluripotency. Conditional reactivation of Lin28 gene in adult mice markedly accelerates the wound-healing process in injured digits. However, little is known about its functions and molecular mechanism in human dental pulp. The aim of this study was to investigate the effects and mechanism of overexpression of Lin28 gene on the proliferation of human dental pulp cells (HDPCs). For this purpose, a number of molecular and biochemical analytical techniques, including the ethynyl-2'-deoxyuridine (EdU) incorporation assay, RNA-protein immunoprecipitation (RIP) analysis, and luciferase assays, were used for detailed characterization. In addition, factors regulating HDPCs activation were explored through gain-of-function and loss-of-function analyses. The results demonstrate that Lin28 promotes cell proliferation and the S-G2/M transition of HDPCs and directly binds to a group of cell cycle regulatory mRNAs in HDPCs. Through bioinformatics analysis and luciferase assays, we confirmed that let-7a targets IGF2BP2. Silencing of IGF2BP2 showed similar cellular and molecular effects as let-7a. Similarly, restoration of IGF2BP2 counteracted the effects of let-7a expression. In conclusion, Lin28 promotes cell proliferation by regulation of both mRNA translation (let-7-independent) and miRNA biogenesis (let-7-dependent). Lin28 can promote the expression of pro-proliferative genes by directly enhancing their translation to maintain a tight control over HDPC proliferation.

Cell Cycle Regulation of Stem Cells by MicroRNAs

MicroRNAs (miRNAs) are a class of small non-coding RNA molecules involved in the regulation of gene expression. They are involved in the fine-tuning of fundamental biological processes such as proliferation, differentiation, survival and apoptosis in many cell types. Emerging evidence suggests that miRNAs regulate critical pathways involved in stem cell function. Several miRNAs have been suggested to target transcripts that directly or indirectly coordinate the cell cycle progression of stem cells. Moreover, previous studies have shown that altered expression levels of miRNAs can contribute to pathological conditions, such as cancer, due to the loss of cell cycle regulation. However, the precise mechanism underlying miRNA-mediated regulation of cell cycle in stem cells is still incompletely understood. In this review, we discuss current knowledge of miRNAs regulatory role in cell cycle progression of stem cells. We describe how specific miRNAs may control cell cycle associated molecules and checkpoints in embryonic, somatic and cancer stem cells. We further outline how these miRNAs could be regulated to influence cell cycle progression in stem cells as a potential clinical application.