miR-29 and miR-30 regulate B-Myb expression during cellular senescence. Proc Natl Acad Sci U S A. 2011;108:522-527. [PMID: 21187425 DOI: 10.1073/pnas.1017346108]

miRNAs and aging: a genetic perspective

A growing body of evidence shows that microRNA expression changes with age in animals ranging from nematode to human. Genetic studies of microRNA function in vivo provide the means to move beyond correlation and to explore cause-effect relationships. Genetic studies in Caenorhabditis elegans and Drosophila have identified cellular pathways involved in organismal aging. Here, we review the evidence that microRNAs act in vivo as regulators of aging pathways, with emphasis on Drosophila.

MicroRNA-29 fine-tunes the expression of key FOXA2-activated lipid metabolism genes and is dysregulated in animal models of insulin resistance and diabetes

MicroRNAs (miRNAs) have emerged as biomarkers of metabolic status, etiological factors in complex disease, and promising drug targets. Recent reports suggest that miRNAs are critical regulators of pathways underlying the pathophysiology of type 2 diabetes. In this study, we demonstrate by deep sequencing and real-time quantitative PCR that hepatic levels of Foxa2 mRNA and miR-29 are elevated in a mouse model of diet-induced insulin resistance. We also show that Foxa2 and miR-29 are significantly upregulated in the livers of Zucker diabetic fatty (fa/fa) rats and that the levels of both returned to normal upon treatment with the insulin-sensitizing agent pioglitazone. We present evidence that miR-29 expression in human hepatoma cells is controlled in part by FOXA2, which is known to play a critical role in hepatic energy homeostasis. Moreover, we demonstrate that miR-29 fine-tunes FOXA2-mediated activation of key lipid metabolism genes, including PPARGC1A, HMGCS2, and ABHD5. These results suggest that miR-29 is an important regulatory factor in normal metabolism and may represent a novel therapeutic target in type 2 diabetes and related metabolic syndromes.

MicroRNAs as Mediators of the Ageing Process

Human ageing is a complex and integrated gradual deterioration of cellular processes. There are nine major hallmarks of ageing, that include changes in DNA repair and DNA damage response, telomere shortening, changes in control over the expression and regulation of genes brought about by epigenetic and mRNA processing changes, loss of protein homeostasis, altered nutrient signaling, mitochondrial dysfunction, stem cell exhaustion, premature cellular senescence and altered intracellular communication. Like practically all other cellular processes, genes associated in features of ageing are regulated by miRNAs. In this review, I will outline each of the features of ageing, together with examples of specific miRNAs that have been demonstrated to be involved in each one. This will demonstrate the interconnected nature of the regulation of transcripts involved in human ageing, and the role of miRNAs in this process. Definition of the factors involved in degeneration of organismal, tissue and cellular homeostasis may provide biomarkers for healthy ageing and increase understanding of the processes that underpin the ageing process itself.

The miR-29 family in hematological malignancies

BACKGROUND

MicroRNAs are short non-coding regulators of gene expression. The human miR-29 family consists of three members: miR-29a, miR-29b and miR-29c. Members of this family were found to be aberrantly expressed in various types of tumors, including hematological malignancies. This family was described to have both oncogenic and tumor suppressor features influencing various pathological processes, such as tumor growth and apoptosis. This review summarizes current knowledge about the miR-29 family in selected hematological malignancies.

CONCLUSION

Recent research of miR-29 family in hematological malignancies has proven its oncogenic as well as tumor suppressive potential. Nevertheless, the level of current evidence is not sufficient, and data remain inconclusive.

Identification of nuclear-enriched miRNAs during mouse granulopoiesis

Background

MicroRNAs (miRNAs) are coordinators of cellular differentiation, including granulopoiesis. Although differential expression of many miRNAs is associated with the maturation of granulocytes, analysis of differentially expressed miRNAs and their cellular localization across all stages of granulopoiesis, starting from hemopoietic stems cells, is not well characterized.

Methods

We analyzed whole cell miRNA and mRNA expression during granulopoiesis using Taqman low-density and Affymetrix arrays respectively. We also performed nuclear and cytoplasmic fractionation followed by Taqman low-density array and/or quantitative PCR to identify nuclear-enriched miRNAs in hemopoietic stem/progenitor cells, promyelocytes, myelocytes, granulocytes and several hemopoietic cell lines. Anti-correlation between the expression of miRNA and target pairs was used to determine putative miRNA targets.

Results

Analyses of our array data revealed distinct clusters of differentially expressed miRNAs that are specific to promyelocytes and granulocytes. While the roles of many of these miRNAs in granulopoiesis are not currently known, anti-correlation of the expression of miRNA/mRNA target pairs identified a suite of novel target genes. Clusters of miRNAs (including members of the let-7 and miR-17-92 families) are downregulated in hemopoietic stem/progenitor cells, potentially allowing the expression of target genes known to facilitate stem cell proliferation and homeostasis. Additionally, four miRNAs (miR-709, miR-706, miR-690 and miR-467a*) were found to be enriched in the nucleus of myeloid cells and multiple hemopoietic cell lines compared to other miRNAs, which are predominantly cytoplasmic-enriched. Both miR-709 and miR-706 are nuclear-enriched throughout granulopoiesis and have putative binding sites of extensive complementarity downstream of pri-miRNAs. Nuclear enrichment of miR-467a* is specific to hemopoietic stem/progenitors and promyelocytes. These miRNAs are also nuclear-enriched in other hemopoietic cell lines, where nuclear sequestering may fine-tune the expression of cytoplasmic mRNA targets.

Conclusions

Overall, we have demonstrated differentially expressed miRNAs that have not previously been associated with hemopoietic differentiation and provided further evidence of regulated nuclear-enrichment of miRNAs. Further studies into miRNA function in granulocyte development may shed light on fundamental aspects of regulatory RNA biology and the role of nuclear miRNAs.

miR-125b induces cellular senescence in malignant melanoma

BACKGROUND

Micro RNAs (miRs) have emerged as key regulators during oncogenesis. They have been found to regulate cell proliferation, differentiation, and apoptosis. Mir-125b has been identified as an oncomir in various forms of tumours, but we have previously proposed that miR-125b is a suppressor of lymph node metastasis in cutaneous malignant melanoma. Our goal was therefore to further examine this theory.

METHODS

We used in-situ-hybridization to visualise miR-125b expression in primary tumours and in lymph node metastasis. Then using a miRVector plasmid containing a miR-125b-1 insert we transfected melanoma cell line Mel-Juso and then investigated the effect of the presence of a stable overexpression of miR-125b on growth by western blotting, flow cytometry and β-galactosidase staining. The tumourogenicity of the transfected cells was tested using a murine model and the tumours were further examined with in-situ-hybridization.

RESULTS

In primary human tumours and in lymph node metastases increased expression of miR-125b was found in single, large tumour cells with abundant cytoplasm. A stable overexpression of miR-125b in human melanoma cell line Mel-Juso resulted in a G0/G1 cell cycle block and emergence of large cells expressing senescence markers: senescence-associated beta-galactosidase, p21, p27 and p53. Mel-Juso cells overexpressing miR-125b were tumourigenic in mice, but the tumours exhibited higher level of cell senescence and decreased expression of proliferation markers, cyclin D1 and Ki67 than the control tumours.

CONCLUSIONS

Our results confirm the theory that miR-125b functions as a tumour supressor in cutaneous malignant melanoma by regulating cellular senescence, which is one of the central mechanisms protecting against the development and progression of malignant melanoma.

High-throughput deep sequencing shows that microRNAs play important roles in switchgrass responses to drought and salinity stress

MicroRNAs (miRNAs) are an important class of small regulatory RNAs. The goal of this study was to analyse stress-responsive miRNAs in switchgrass (Panicum virgatum), the emerging biofuel crop, to facilitate choosing gene targets for improving biomass and biofuel yield. After sequencing three small RNA libraries constructed from control, salt- and drought-treated switchgrass using Illumina sequencing technology, we identified 670 known miRNA families from a total of more than 50 million short reads. A total of 273 miRNAs were identified with precursors: 126 conserved miRNAs and 147 novel miRNAs. Of them, 265 miRNAs were found to have their opposite sequences (miRNA*) with 2-nt overhang on the 3' end. Of them, 194 were detected in switchgrass transcriptome sequences generated from 31 high-throughput RNA sequencing (RNA-Seq) data sets in NCBI. Many miRNAs were differentially or uniquely expressed during salinity or drought stress treatment. We also discovered 11 miRNA clusters containing 29 miRNAs. These identified miRNAs potentially targeted 28549 genes with a various function, including transcription factors, stress-response proteins and cellulose biosynthesis-related proteins. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the identified miRNAs and their targets were classified to 3779 GO terms including 1534 molecular functions, 1851 biological processes and 394 cellular components and were enriched to 147 KEGG pathways. Interestingly, 195 miRNA families and 450 targets were involved in the biosynthesis pathways of carbon, glucose, starch, fatty acid and lignin and in xylem formation, which could aid in designing next-generation switchgrass for biomass and biofuel.

miR-30-5p functions as a tumor suppressor and novel therapeutic tool by targeting the oncogenic Wnt/β-catenin/BCL9 pathway

Wnt/β-catenin signaling underlies the pathogenesis of a broad range of human cancers, including the deadly plasma cell cancer multiple myeloma. In this study, we report that downregulation of the tumor suppressor microRNA miR-30-5p is a frequent pathogenetic event in multiple myeloma. Evidence was developed that miR-30-5p downregulation occurs as a result of interaction between multiple myeloma cells and bone marrow stromal cells, which in turn enhances expression of BCL9, a transcriptional coactivator of the Wnt signaling pathway known to promote multiple myeloma cell proliferation, survival, migration, drug resistance, and formation of multiple myeloma cancer stem cells. The potential for clinical translation of strategies to re-express miR-30-5p as a therapeutic approach was further encouraged by the capacity of miR-30c and miR-30 mix to reduce tumor burden and metastatic potential in vivo in three murine xenograft models of human multiple myeloma without adversely affecting associated bone disease. Together, our findings offer a preclinical rationale to explore miR-30-5p delivery as an effective therapeutic strategy to eradicate multiple myeloma cells in vivo.

Mir-29 repression in bladder outlet obstruction contributes to matrix remodeling and altered stiffness

Recent work has uncovered a role of the microRNA (miRNA) miR-29 in remodeling of the extracellular matrix. Partial bladder outlet obstruction is a prevalent condition in older men with prostate enlargement that leads to matrix synthesis in the lower urinary tract and increases bladder stiffness. Here we tested the hypothesis that miR-29 is repressed in the bladder in outlet obstruction and that this has an impact on protein synthesis and matrix remodeling leading to increased bladder stiffness. c-Myc, NF-κB and SMAD3, all of which repress miR-29, were activated in the rat detrusor following partial bladder outlet obstruction but at different times. c-Myc and NF-κB activation occurred early after obstruction, and SMAD3 phosphorylation increased later, with a significant elevation at 6 weeks. c-Myc, NF-κB and SMAD3 activation, respectively, correlated with repression of miR-29b and miR-29c at 10 days of obstruction and with repression of miR-29c at 6 weeks. An mRNA microarray analysis showed that the reduction of miR-29 following outlet obstruction was associated with increased levels of miR-29 target mRNAs, including mRNAs for tropoelastin, the matricellular protein Sparc and collagen IV. Outlet obstruction increased protein levels of eight out of eight examined miR-29 targets, including tropoelastin and Sparc. Transfection of human bladder smooth muscle cells with antimiR-29c and miR-29c mimic caused reciprocal changes in target protein levels in vitro. Tamoxifen inducible and smooth muscle-specific deletion of Dicer in mice reduced miR-29 expression and increased tropoelastin and the thickness of the basal lamina surrounding smooth muscle cells in the bladder. It also increased detrusor stiffness independent of outlet obstruction. Taken together, our study supports a model where the combined repressive influences of c-Myc, NF-κB and SMAD3 reduce miR-29 in bladder outlet obstruction, and where the resulting drop in miR-29 contributes to matrix remodeling and altered passive mechanical properties of the detrusor.

The inhibitory role of Mir-29 in growth of breast cancer cells

Mir-29 microRNA families are involved in regulation of various types of cancers. Although Mir-29 was shown to play an inhibitory role in tumorigenesis, the role of Mir-29 in breast cancer still remains obscure. In this study, we showed that Mir-29a is the dominant isoform in its family in mammary cells and expression of Mir-29a was down-regulated in different types of breast cancers. Furthermore, over-expression of Mir-29a resulted in significant slower growth of breast cancer cells and caused higher percentage of cells at G0/G1 phase. Consistent with this over-expression data, knockdown of Mir-29a in normal mammary cells lead to higher cell growth rate, and higher percentage of cells entering S phase. We further found that Mir-29a negatively regulated expression of B-Myb, which is a transcription factor associated with tumorigenesis. The protein levels of Cyclin A2 and D1 are consistent with the protein level of B-Myb. Taken together, our data suggests Mir-29a plays an important role in inhibiting growth of breast cancer cells and arresting cells at G0/G1 phase. Our data also suggests that Mir-29a may suppress tumor growth through down-regulating B-Myb.

Individual and combined effects of DNA methylation and copy number alterations on miRNA expression in breast tumors

Background

The global effect of copy number and epigenetic alterations on miRNA expression in cancer is poorly understood. In the present study, we integrate genome-wide DNA methylation, copy number and miRNA expression and identify genetic mechanisms underlying miRNA dysregulation in breast cancer.

Results

We identify 70 miRNAs whose expression was associated with alterations in copy number or methylation, or both. Among these, five miRNA families are represented. Interestingly, the members of these families are encoded on different chromosomes and are complementarily altered by gain or hypomethylation across the patients. In an independent breast cancer cohort of 123 patients, 41 of the 70 miRNAs were confirmed with respect to aberration pattern and association to expression. In vitro functional experiments were performed in breast cancer cell lines with miRNA mimics to evaluate the phenotype of the replicated miRNAs. let-7e-3p, which in tumors is found associated with hypermethylation, is shown to induce apoptosis and reduce cell viability, and low let-7e-3p expression is associated with poorer prognosis. The overexpression of three other miRNAs associated with copy number gain, miR-21-3p, miR-148b-3p and miR-151a-5p, increases proliferation of breast cancer cell lines. In addition, miR-151a-5p enhances the levels of phosphorylated AKT protein.

Conclusions

Our data provide novel evidence of the mechanisms behind miRNA dysregulation in breast cancer. The study contributes to the understanding of how methylation and copy number alterations influence miRNA expression, emphasizing miRNA functionality through redundant encoding, and suggests novel miRNAs important in breast cancer.

Profile of cerebrospinal microRNAs in fibromyalgia

Introduction

Fibromyalgia (FM) is characterized by chronic pain and reduced pain threshold. The pathophysiology involves disturbed neuroendocrine function, including impaired function of the growth hormone/insulin-like growth factor-1 axis. Recently, microRNAs have been shown to be important regulatory factors in a number of diseases.

The aim of this study was to try to identify cerebrospinal microRNAs with expression specific for FM and to determine their correlation to pain and fatigue.

Methods

The genome-wide profile of microRNAs in cerebrospinal fluid was assessed in ten women with FM and eight healthy controls using real-time quantitative PCR. Pain thresholds were examined by algometry. Levels of pain (FIQ pain) were rated on a 0-100 mm scale (fibromyalgia impact questionnaire, FIQ). Levels of fatigue (FIQ fatigue) were rated on a 0-100 mm scale using FIQ and by multidimensional fatigue inventory (MFI-20) general fatigue (MFIGF).

Results

Expression levels of nine microRNAs were significantly lower in patients with FM patients compared to healthy controls. The microRNAs identified were miR-21-5p, miR-145-5p, miR-29a-3p, miR-99b-5p, miR-125b-5p, miR-23a-3p, 23b-3p, miR-195-5p, miR-223-3p.

The identified microRNAs with significantly lower expression in FM were assessed with regard to pain and fatigue. miR-145-5p correlated positively with FIQ pain (r=0.709, p=0.022, n=10) and with FIQ fatigue (r=0.687, p=0.028, n=10).

Conclusion

To our knowledge, this is the first study to show a disease-specific pattern of cerebrospinal microRNAs in FM.

We have identified nine microRNAs in cerebrospinal fluid that differed between FM patients and healthy controls. One of the identified microRNAs, miR-145 was associated with the cardinal symptoms of FM, pain and fatigue.

MiR-30a-5p connects EWS-FLI1 and CD99, two major therapeutic targets in Ewing tumor

Ewing sarcoma is a pediatric bone tumor characterized in 85% of cases by the fusion between EWS and FLI1 genes that results in the expression of the EWS-FLI1 aberrant transcription factor. Histologically, the Ewing tumor expresses high levels of the CD99 membrane glycoprotein. It has been recently described that CD99 expression contributes to the Ewing tumor oncogenesis by modulating growth and differentiation of tumor cells. Different studies have also shown that overexpression of EWS-FLI1 induces CD99 expression in non-Ewing cells. At the opposite, the knockdown of EWS-FLI1 expression by siRNA approaches has no significant effect on CD99 mRNA level in Ewing cells. Here, by in vivo and in vitro studies, we show that while EWS-FLI1 inhibition has only slight effects on the amount of CD99 transcript, it induces a dramatic decrease of the CD99 protein expression level, hence suggesting post-transcriptional regulations, possibly mediated by microRNAs. To further investigate this issue, we identified a set of 91 miRNAs that demonstrate EWS-FLI1 modulation, three of them being predicted to bind CD99 3' untranslated region (30'UTR). Among these, we show that miR-30a-5p has the ability to interact with the 30'UTR region of CD99 and to regulate its expression. Moreover, the re-expression of miRNA-30a-5p in Ewing cell line induces decreased cell proliferation and invasion. In this study, we therefore show that miR-30a-5p constitutes a major functional link between EWS-FLI1 and CD99, two critical biomarkers and therapeutic targets in Ewing sarcoma.

Adverse prognostic value of MYBL2 overexpression and association with microRNA-30 family in acute myeloid leukemia patients

The MYBL2 gene encodes a transcription factor implicated in cell proliferation and maturation whose amplification or overexpression has been associated with different human malignancies, suggesting that it could be implicated in tumorigenesis. We analyzed MYBL2 expression and its prognostic value in 291 patients with de novo acute myeloid leukemia (AML) and we also evaluated its association with microRNAs 29 and 30 families. MYBL2 expression in AML patients was increased relative to CD34+ cells. Moreover, MYBL2 overexpression was associated with lower expression of miR-30a (P=0.024), miR-30b (P=0.021) and miR-30c (P=0.009). Multivariate analysis showed that MYBL2 expression was an independent factor for disease-free survival (HR 3.0, 95% CI 1.5-6.0, P=0.002) and cumulative incidence of relapse (HR 2.6, 95% CI 1.2-5.6, P=0.015) in patients with an intermediate-risk karyotype. In conclusion, our data showed that MYBL2 expression analysis could be useful to define subgroups of patients with poor prognosis.

MicroRNAs induced in melanoma treated with combination targeted therapy of Temsirolimus and Bevacizumab

Background

Targeted therapies directed at commonly overexpressed pathways in melanoma have clinical activity in numerous trials. Little is known about how these therapies influence microRNA (miRNA) expression, particularly with combination regimens. Knowledge of miRNAs altered with treatment may contribute to understanding mechanisms of therapeutic effects, as well as mechanisms of tumor escape from therapy. We analyzed miRNA expression in metastatic melanoma tissue samples treated with a novel combination regimen of Temsirolimus and Bevacizumab. Given the preliminary clinical activity observed with this combination regimen, we hypothesized that we would see significant changes in miRNA expression with combination treatment.

Methods

Using microarray analysis we analyzed miRNA expression levels in melanoma samples from a Cancer Therapy Evaluation Program-sponsored phase II trial of combination Temsirolimus and Bevacizumab in advanced melanoma, which elicited clinical benefit in a subset of patients. Pre-treatment and post-treatment miRNA levels were compared using paired t-tests between sample groups (patients), using a p-value < 0.01 for significance.

Results

microRNA expression remained unchanged with Temsirolimus alone; however, expression of 15 microRNAs was significantly upregulated (1.4 to 2.5-fold) with combination treatment, compared to pre-treatment levels. Interestingly, twelve of these fifteen miRNAs possess tumor suppressor capabilities. We identified 15 putative oncogenes as potential targets of the 12 tumor suppressor miRNAs, based on published experimental evidence. For 15 of 25 miRNA-target mRNA pairings, changes in gene expression from pre-treatment to post-combination treatment samples were inversely correlated with changes in miRNA expression, supporting a functional effect of those miRNA changes. Clustering analyses based on selected miRNAs suggest preliminary signatures characteristic of clinical response to combination treatment and of tumor BRAF mutational status.

Conclusions

To our knowledge, this is the first study analyzing miRNA expression in pre-treatment and post-treatment human metastatic melanoma tissue samples. This preliminary investigation suggests miRNAs that may be involved in the mechanism of action of combination Temsirolimus and Bevacizumab in metastatic melanoma, possibly through inhibition of oncogenic pathways, and provides the preliminary basis for further functional studies of these miRNAs.

Downregulation of microRNA-30 facilitates podocyte injury and is prevented by glucocorticoids

MicroRNAs (miRNAs) are essential for podocyte homeostasis, and the miR-30 family may be responsible for this action. However, the exact roles and clinical relevance of miR-30s remain unknown. In this study, we examined the expression of the miR-30 family in the podocytes of patients with FSGS and found that all members are downregulated. Treating cultured human podocytes with TGF-β, LPS, or puromycin aminonucleoside (PAN) also downregulated the miR-30 family. Podocyte cytoskeletal damage and apoptosis caused by treatment with TGF-β or PAN were ameliorated by exogenous miR-30 expression and aggravated by miR-30 knockdown. Moreover, we found that miR-30s exert their protective roles by direct inhibition of Notch1 and p53, which mediate podocyte injury. In rats, treatment with PAN substantially downregulated podocyte miR-30s and induced proteinuria and podocyte injury; however, transfer of exogenous miR-30a to podocytes of PAN-treated rats ameliorated proteinuria and podocyte injury and reduced Notch1 activation. Finally, we demonstrated that glucocorticoid treatment maintains miR-30 expression in cultured podocytes treated with TGF-β, LPS, or PAN and in the podocytes of PAN-treated rats. Glucocorticoid-sustained miR-30 expression associated with reduced Notch1 activation and alleviated podocyte damage. Taken together, these findings demonstrate that miR-30s protect podocytes by targeting Notch1 and p53 and that the loss of miR-30s facilitates podocyte injury. In addition, sustained miR-30 expression may be a novel mechanism underlying the therapeutic effectiveness of glucocorticoids in treating podocytopathy.

MicroRNAs linking inflamm-aging, cellular senescence and cancer

Epidemiological and experimental data demonstrate a strong correlation between age-related chronic inflammation (inflamm-aging) and cancer development. However, a comprehensive approach is needed to clarify the underlying molecular mechanisms. Chronic inflammation has mainly been attributed to continuous immune cells activation, but the cellular senescence process, which may involve acquisition of a senescence-associated secretory phenotype (SASP), can be another important contributor, especially in the elderly. MicroRNAs (miRs), a class of molecules involved in gene expression regulation, are emerging as modulators of some pathways, including NF-κB, mTOR, sirtuins, TGF-β and Wnt, that may be related to inflammation, cellular senescence and age-related diseases, cancer included. Interestingly, cancer development is largely avoided or delayed in centenarians, where changes in some miRs are found in plasma and leukocytes. We identified miRs that can be considered as senescence-associated (SA-miRs), inflammation-associated (inflamma-miRs) and cancer-associated (onco-miRs). Here we review recent findings concerning three of them, miR-21, -126 and -146a, which target mRNAs belonging to the NF-κB pathway; we discuss their ability to link cellular senescence, inflamm-aging and cancer and their changes in centenarians, and provide an update on the possibility of using miRs to block accumulation of senescent cells to prevent formation of a microenvironment favoring cancer development and progression.

MYBL2 is a sub-haploinsufficient tumor suppressor gene in myeloid malignancy

A common deleted region (CDR) in both myelodysplastic syndromes (MDS) and myeloproliferative neoplasms (MPN) affects the long arm of chromosome 20 and has been predicted to harbor a tumor suppressor gene. Here we show that MYBL2, a gene within the 20q CDR, is expressed at sharply reduced levels in CD34+ cells from most MDS cases (65%; n = 26), whether or not they harbor 20q abnormalities. In a murine competitive reconstitution model, Mybl2 knockdown by RNAi to 20-30% of normal levels in multipotent hematopoietic progenitors resulted in clonal dominance of these 'sub-haploinsufficient' cells, which was reflected in all blood cell lineages. By 6 months post-transplantation, the reconstituted mice had developed a clonal myeloproliferative/myelodysplastic disorder originating from the cells with aberrantly reduced Mybl2 expression. We conclude that downregulation of MYBL2 activity below levels predicted by classical haploinsufficiency underlies the clonal expansion of hematopoietic progenitors in a large fraction of human myeloid malignancies. DOI:http://dx.doi.org/10.7554/eLife.00825.001.

MicroRNA-30a suppresses breast tumor growth and metastasis by targeting metadherin

Accumulating data have shown the involvement of microRNAs in cancerous processes as either oncogenes or tumor suppressor genes. Here, we established miR-30a as a tumor suppressor gene in breast cancer development and metastasis. Ectopic expression of miR-30a in breast cancer cell lines resulted in the suppression of cell growth and metastasis in vitro. Consistently, the xenograft mouse model also unveiled the suppressive effects of miR-30a on tumor growth and distal pulmonary metastasis. With dual luciferase reporter assay, we revealed that miR-30a could bind to the 3'-untranslated region of metadherin (MTDH) gene, thus exerting inhibitory effect on MTDH. Furthermore, we demonstrated that silence of MTDH could recapitulate the effects of miR-30a overexpression, while overexpression of MTDH could partially abrogate miR-30a-mediated suppression. Of significance, expression level of miR-30a was found to be significantly lower in primary breast cancer tissues than in the paired normal tissues. Further evaluation verified that miR-30a was negatively correlated with the extent of lymph node and lung metastasis in patients with breast cancer. Taken together, our findings indicated miR-30a inhibits breast cancer proliferation and metastasis by directly targeting MTDH, and miR-30a can serve as a prognostic marker for breast cancer. Manipulation of miR-30a may provide a promising therapeutic strategy for breast cancer treatment.

Ten-eleven translocation (Tet) and thymine DNA glycosylase (TDG), components of the demethylation pathway, are direct targets of miRNA-29a

The ten-eleven translocation family of proteins (Tet1/2/3, Tets) converts 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), which can be further oxidized and repaired by thymine DNA glycosylase (TDG), to influence gene transcription in embryonic and adult tissues. However the mechanisms of how Tets and TDG levels are regulated are unknown. We show that miR-29 can directly regulate Tet1-3 and TDG mRNA levels through binding to their 3'UTRs. miR-29 mimic decreases global 5hmC levels, a hallmark of Tet activity. Moreover, the mRNA levels for Tet3 and TDG are inversely correlated with the levels of miR-29 in aged mouse aorta implying that aging may affect methylation patterns via miRNA. In summary, our data show that Tets and TDG are direct targets of miR-29 and unravel a novel regulatory role for this miRNA in epigenetic DNA demethylation pathways.

miR-30 as a tumor suppressor connects EGF/Src signal to ERG and EMT

Src tyrosine kinase (Src) is implicated in the development of bone metastasis and castration resistance of prostate cancer. Src inhibitors are currently being tested in clinical trials for such diseases. Understanding the molecular and cellular actions of Src inhibitors holds the key to future improvement of this line of therapy. Here we describe the microRNA expression profiles modulated by two Src inhibitors and demonstrate that the miR-30 family members are the most prominently induced species. Consistent with its tumor suppressor role, miR-30 is downmodulated by oncogenic signals such as epidermal growth factor (EGF) and hepatocyte growth factor, and is generally underexpressed in prostate cancer specimens. A number of epithelial-to-mesenchymal transition (EMT)-associated genes are predicted targets of miR-30. Among these genes the Ets-related gene (ERG) is the most frequently overexpressed oncogene in prostate cancer activated by genomic fusion events between promoter upstream sequences of the TMPRSS2 and coding sequences of ERG. We showed by ERG 3' untranslated region reporter and mutagenesis assays that ERG is a direct target of miR-30. Overexpression of miR-30 in prostate cancer cells suppresses EMT phenotypes and inhibits cell migration and invasion. It also inhibits the in vitro and in vivo growth of VCaP cells, which depends on TMPRSS2-ERG for proliferation. TMPRSS2-ERG is generally regulated by androgen at the transcriptional level. Our finding reveals a new post-transcriptional mechanism of TMPRSS2-ERG regulation by Src and growth signals via miR-30 providing a rationale for targeting ERG-positive castration-resistant tumors with Src inhibitors.

MicroRNAs and their roles in aging

MicroRNAs (miRNAs) are a class of short non-coding RNAs that bind mRNAs through partial base-pair complementarity with their target genes, resulting in post-transcriptional repression of gene expression. The role of miRNAs in controlling aging processes has been uncovered recently with the discovery of miRNAs that regulate lifespan in the nematode Caenorhabditis elegans through insulin and insulin-like growth factor-1 signaling and DNA damage checkpoint factors. Furthermore, numerous miRNAs are differentially expressed during aging in C. elegans, but the specific functions of many of these miRNAs are still unknown. Recently, various miRNAs have been identified that are up- or down-regulated during mammalian aging by comparing their tissue-specific expression in younger and older mice. In addition, many miRNAs have been implicated in governing senescence in a variety of human cell lines, and the precise functions of some of these miRNAs in regulating cellular senescence have helped to elucidate mechanisms underlying aging. In this Commentary, we review the various regulatory roles of miRNAs during aging processes. We highlight how certain miRNAs can regulate aging on the level of organism lifespan, tissue aging or cellular senescence. Finally, we discuss future approaches that might be used to investigate the mechanisms by which miRNAs govern aging processes.

Analysis of hsa-miR-30a-5p expression in human gliomas

Our previous study demonstrated that miR-30a-5p was upregulated in six malignant glioma cell lines by microRNA(miRNA) array. For further verification of this finding, the expression of miR-30a-5p in 7 more malignant glioma cell lines, 43 freshly resected glioma samples and 75 archival paraffin embedded glioma specimens with different grade of malignancy were examined by qRT-PCR and in situ hybridization(ISH). Here, we present the first evidence that miR-30a-5p is overexpressed in glioma cell lines and glioma samples as compared to the normal brain tissues (NBTs), and its expression level is positively correlated with tumor grade of malignancy. It is concluded that miR-30a-5p may have the potential as a diagnostic or prognostic marker of gliomas and as the target of miRNA-based glioma therapy in further studies.

The role of exosomes and microRNAs in senescence and aging

Senescence is viewed as a cellular counterpart to aging of tissues and organisms, characterized by an irreversible growth arrest and a combination of changes in cell morphology, function and behavior. microRNAs (miRNAs), the most studied small non-coding RNAs, play an important role in many biological processes by the regulation of gene expression. Recent evidence has shown that miRNAs are contained in exosomes that are tiny vesicles of endocytic origin and released by a variety of different cells as a means for cell-to-cell contact and information transfer. Exosomes and miRNAs have been found to participate in the complex networks of cellular senescence and contribute to aging. Here, we will give an overview on the involvement of secretory factors including exosomes and miRNA in the regulation of cellular senescence, demonstrating the potential role of exosomes and miRNAs in biological processes and signaling pathways of senescence and aging.

MicroRNA miR-30 family regulates non-attachment growth of breast cancer cells

BACKGROUND

A subset of breast cancer cells displays increased ability to self-renew and reproduce breast cancer heterogeneity. The characterization of these so-called putative breast tumor-initiating cells (BT-ICs) may open the road for novel therapeutic strategies. As microRNAs (miRNAs) control developmental programs in stem cells, BT-ICs may also rely on specific miRNA profiles for their sustained activity. To explore the notion that miRNAs may have a role in sustaining BT-ICs, we performed a comprehensive profiling of miRNA expression in a model of putative BT-ICs enriched by non-attachment growth conditions.

RESULTS

We found breast cancer cells grown under non-attachment conditions display a unique pattern of miRNA expression, highlighted by a marked low expression of miR-30 family members relative to parental cells. We further show that miR-30a regulates non-attachment growth. A target screening revealed that miR-30 family redundantly modulates the expression of apoptosis and proliferation-related genes. At least one of these targets, the anti-apoptotic protein AVEN, was able to partially revert the effect of miR-30a overexpression. Finally, overexpression of miR-30a in vivo was associated with reduced breast tumor progression.

CONCLUSIONS

miR30-family regulates the growth of breast cancer cells in non-attachment conditions. This is the first analysis of target prediction in a whole family of microRNAs potentially involved in survival of putative BT-ICs.

The role of miRNA-29 family in cancer

The miRNA-29 family of microRNAs (miRNAs), including miR-29a, miR-29b and miR-29c, was recently reported to be aberrantly expressed in multiple cancers. Increasing evidence shows that the abnormal expression of miR-29 family is associated with tumorigenesis and cancer progression, making miR-29s a well-analyzed group of miRNAs in cancer research. Here, in this review we aim to provide an overview of the role of miR-29 family in the pathophysiologic changes of cancer cells and the epigenetic and immune regulation through the biological function of miR-29s.

MicroRNAs in age-related diseases

Aging is a complex process that is linked to an increased incidence of major diseases such as cardiovascular and neurodegenerative disease, but also cancer and immune disorders. MicroRNAs (miRNAs) are small non-coding RNAs, which post-transcriptionally control gene expression by inhibiting translation or inducing degradation of targeted mRNAs. MiRNAs target up to hundreds of mRNAs, thereby modulating gene expression patterns. Many miRNAs appear to be dysregulated during cellular senescence, aging and disease. However, only few miRNAs have been so far linked to age-related changes in cellular and organ functions. The present article will discuss these findings, specifically focusing on the cardiovascular and neurological systems.

MiR-30-regulated autophagy mediates angiotensin II-induced myocardial hypertrophy

Dysregulated autophagy may lead to the development of disease. Role of autophagy and the diagnostic potential of microRNAs that regulate the autophagy in cardiac hypertrophy have not been evaluated. A rat model of cardiac hypertrophy was established using transverse abdominal aortic constriction (operation group). Cardiomyocyte autophagy was enhanced in rats from the operation group, compared with those in the sham operation group. Moreover, the operation group showed up-regulation of beclin-1 (an autophagy-related gene), and down-regulation of miR-30 in cardiac tissue. The effects of inhibition and over-expression of the beclin-1 gene on the expression of hypertrophy-related genes and on autophagy were assessed. Angiotensin II-induced myocardial hypertrophy was found to be mediated by over-expression of the beclin-1 gene. A dual luciferase reporter assay confirmed that beclin-1 was a target gene of miR-30a. miR-30a induced alterations in beclin-1 gene expression and autophagy in cardiomyocytes. Treatment of cardiomyocytes with miR-30a mimic attenuated the Angiotensin II-induced up-regulation of hypertrophy-related genes and decreased in the cardiomyocyte surface area. Conversely, treatment with miR-30a inhibitor enhanced the up-regulation of hypertrophy-related genes and increased the surface area of cardiomyocytes induced by Angiotensin II. In addition, circulating miR-30 was elevated in patients with left ventricular hypertrophy, and circulating miR-30 was positively associated with left ventricular wall thickness. Collectively, these above-mentioned results suggest that Angiotensin II induces down-regulation of miR-30 in cardiomyocytes, which in turn promotes myocardial hypertrophy through excessive autophagy. Circulating miR-30 may be an important marker for the diagnosis of left ventricular hypertrophy.

Decreased microRNA-30a levels are associated with enhanced ABL1 and BCR-ABL1 expression in chronic myeloid leukemia

Chronic myeloid leukemia (CML) is associated with overexpression of BCR-ABL1, a nonreceptor tyrosine kinase critical for malignant transformation. We investigated whether non-coding microRNAs (miRNAs) targeting BCR-ABL1 mRNA contribute to the pathogenesis of CML. Indeed, miR-30a targeted BCR-ABL1 and was underexpressed in bone marrow from CML patients. In K562 leukemia cells, overexpression of miR-30a reduced ABL1 and BCR-ABL1 protein expression, decreased proliferation, and arrested cell cycle progression between G1 and S. These findings strongly suggest that miR-30a acts as a tumor suppressor by downregulating ABL1 and BCR-ABL1 expression. Upregulation of miR-30a in hematopoietic cells may have therapeutic efficacy against CML.

Markers of cellular senescence

Cellular senescence is a tumor suppression mechanism that evolved to limit duplication in somatic cells. Senescence is imposed by natural replicative boundaries or stress-induced signals, such as oncogenic transformation. Neoplastic cells can be forced to undergo senescence through genetic manipulations and epigenetic factors, including anticancer drugs, radiation, and differentiating agents. Senescent cells show distinct phenotypic and molecular characteristics, both in vitro or in vivo. These biomarkers might either cause or result from senescence induction, but could also be the byproducts of physiological changes in these non-replicating cells.

mir-30d Regulates multiple genes in the autophagy pathway and impairs autophagy process in human cancer cells

In human epithelial cancers, the microRNA (miRNA) mir-30d is amplified with high frequency and serves as a critical oncomir by regulating metastasis, apoptosis, proliferation, and differentiation. Autophagy, a degradation pathway for long-lived protein and organelles, regulates the survival and death of many cell types. Increasing evidence suggests that autophagy plays an important function in epithelial tumor initiation and progression. Using a combined bioinformatics approach, gene set enrichment analysis, and miRNA target prediction, we found that mir-30d might regulate multiple genes in the autophagy pathway including BECN1, BNIP3L, ATG12, ATG5, and ATG2. Our further functional experiments demonstrated that the expression of these core proteins in the autophagy pathway was directly suppressed by mir-30d in cancer cells. Finally, we showed that mir-30d regulated the autophagy process by inhibiting autophagosome formation and LC3B-I conversion to LC3B-II. Taken together, our results provide evidence that the oncomir mir-30d impairs the autophagy process by targeting multiple genes in the autophagy pathway. This result will contribute to understanding the molecular mechanism of mir-30d in tumorigenesis and developing novel cancer therapy strategy.

A microRNA network regulates proliferative timing and extracellular matrix synthesis during cellular quiescence in fibroblasts

Background

Although quiescence (reversible cell cycle arrest) is a key part in the life history and fate of many mammalian cell types, the mechanisms of gene regulation in quiescent cells are poorly understood. We sought to clarify the role of microRNAs as regulators of the cellular functions of quiescent human fibroblasts.

Results

Using microarrays, we discovered that the expression of the majority of profiled microRNAs differed between proliferating and quiescent fibroblasts. Fibroblasts induced into quiescence by contact inhibition or serum starvation had similar microRNA profiles, indicating common changes induced by distinct quiescence signals. By analyzing the gene expression patterns of microRNA target genes with quiescence, we discovered a strong regulatory function for miR-29, which is downregulated with quiescence. Using microarrays and immunoblotting, we confirmed that miR-29 targets genes encoding collagen and other extracellular matrix proteins and that those target genes are induced in quiescence. In addition, overexpression of miR-29 resulted in more rapid cell cycle re-entry from quiescence. We also found that let-7 and miR-125 were upregulated in quiescent cells. Overexpression of either one alone resulted in slower cell cycle re-entry from quiescence, while the combination of both together slowed cell cycle re-entry even further.

Conclusions

microRNAs regulate key aspects of fibroblast quiescence including the proliferative state of the cells as well as their gene expression profiles, in particular, the induction of extracellular matrix proteins in quiescent fibroblasts.

Discovery of MicroRNAs associated with myogenesis by deep sequencing of serial developmental skeletal muscles in pigs

MicroRNAs (miRNAs) are short, single-stranded non-coding RNAs that repress their target genes by binding their 3′ UTRs. These RNAs play critical roles in myogenesis. To gain knowledge about miRNAs involved in the regulation of myogenesis, porcine longissimus muscles were collected from 18 developmental stages (33-, 40-, 45-, 50-, 55-, 60-, 65-, 70-, 75-, 80-, 85-, 90-, 95-, 100- and 105-day post-gestation fetuses, 0 and 10-day postnatal piglets and adult pigs) to identify miRNAs using Solexa sequencing technology. We detected 197 known miRNAs and 78 novel miRNAs according to comparison with known miRNAs in the miRBase (release 17.0) database. Moreover, variations in sequence length and single nucleotide polymorphisms were also observed in 110 known miRNAs. Expression analysis of the 11 most abundant miRNAs were conducted using quantitative PCR (qPCR) in eleven tissues (longissimus muscles, leg muscles, heart, liver, spleen, lung, kidney, stomach, small intestine and colon), and the results revealed that ssc-miR-378, ssc-miR-1 and ssc-miR-206 were abundantly expressed in skeletal muscles. During skeletal muscle development, the expression level of ssc-miR-378 was low at 33 days post-coitus (dpc), increased at 65 and 90 dpc, peaked at postnatal day 0, and finally declined and maintained a comparatively stable level. This expression profile suggested that ssc-miR-378 was a new candidate miRNA for myogenesis and participated in skeletal muscle development in pigs. Target prediction and KEGG pathway analysis suggested that bone morphogenetic protein 2 (BMP2) and mitogen-activated protein kinase 1 (MAPK1), both of which were relevant to proliferation and differentiation, might be the potential targets of miR-378. Luciferase activities of report vectors containing the 3′UTR of porcine BMP2 or MAPK1 were downregulated by miR-378, which suggested that miR-378 probably regulated myogenesis though the regulation of these two genes.

From cellular senescence to age-associated diseases: the miRNA connection

Cellular senescence has evolved from an in-vitro model system to study aging in vitro to a multifaceted phenomenon of in-vivo importance as senescent cells in vivo have been identified and their removal delays the onset of age-associated diseases in a mouse model system. From the large emerging class of non-coding RNAs, miRNAs have only recently been functionally implied in the regulatory networks that are modified during the aging process. Here we summarize examples of similarities between the differential expression of miRNAs during senescence and age-associated diseases and suggest that these similarities might emphasize the importance of senescence for the pathogenesis of age-associated diseases. Understanding such a connection on the level of miRNAs might offer valuable opportunities for designing novel diagnostic and therapeutic strategies.

Micro-RNA30c negatively regulates REDD1 expression in human hematopoietic and osteoblast cells after gamma-irradiation

We recently demonstrated that a novel cell stress response gene REDD1 protects human fetal osteoblast cell line (hFOB) cells from γ-radiation-induced premature senescence. Here we show that levels of endogenous REDD1 are very low in human hematopoietic progenitor CD34+ cells regardless of radiation, but highly expressed in differentiated hematopoietic cells (14 day cultured CD34+ cells) in response to radiation, which might be associated with radiation tolerance of the latter cells. To further understand the mechanisms of radiation-induced damage in different cells, microRNA (miRNA)-arrays were performed using purified miRNAs from CD34+ and hFOB cells before and post-irradiation and real-time reverse transcription (RT)-PCR was used to validate the expression profiles of miRNAs in the radiation-damaged cells. The results indicate that γ-radiation downregulated 16 miRNAs in CD34+ cells and 14 in hFOB cells. Radiation-induced upregulation was observed for 15 miRNAs in CD34+ cells and 18 miRNAs in hFOB cells. The profiles of radiation-induced miRNA expression were completely different in CD34+ vs. hFOB cells. Radiation up-regulated miRNA (miR)-30b, miR-30c and miR-30d in CD34+ cells, whereas it inhibited miR-30c expression in hFOB cells. Since miR-30 has potential target sites located in the 3'untranslated region (UTR) of the REDD1 gene and radiation regulated miR-30c expression in both CD34+ and hFOB cells, we further explored the effects of miR-30c on REDD1 expression using miR-30c inhibitor and precursor (pre-miR-30c). The results show that pre-miR-30c transfection suppressed REDD1 expression in 14 day cultured CD34+ cells and hFOB cells and resulted in hFOB cell death. In contrast, inhibition of miR-30c expression significantly enhanced clonogenicity in CD34+ cells. Our data suggest that CD34+ and hFOB cells have different miRNA expression patterns after irradiation and miR-30c plays a key role in radiation-induced cell damage which might be through regulation of REDD1 expression.

Reduction of type IV collagen by upregulated miR-29 in normal elderly mouse and klotho-deficient, senescence-model mouse

MicroRNA (miRNA), a small non-coding RNA that functions as a mediator in gene silencing, plays important roles in gene regulation in various vital functions and activities. Here we show that the miR-29 members are upregulated in klotho-deficient [klotho(−/−)] mice, a senescence-model animal, and also in normal elderly ICR mice relative to wild-type littermates and young ICR mice. In addition, levels of type IV collagen, a major component of basement membranes and a putative target of miR-29, were lower in klotho(−/−) and elderly ICR mice than in wild-type littermates and young ICR mice. RNA degradation mediated by miR-29 may participate in the suppression of type IV collagen, both in vivo and in vitro. Taken together, our current findings suggest that the miR-29 upregulated in aging may be involved in the downregulation of type IV collagen, leading to a possible weakening of the basal membrane in senescent tissues, and miR-29 may be a useful molecular marker of senescence.

The microRNA-30 family targets DLL4 to modulate endothelial cell behavior during angiogenesis

Delta-like 4 (DLL4), a membrane-bound ligand belonging to the Notch signaling family, plays a fundamental role in vascular development and angiogenesis. We identified a conserved microRNA family, miR-30, which targets DLL4. Overexpression of miR-30b in endothelial cells led to increased vessel number and length in an in vitro model of sprouting angiogenesis. Microinjection of miR-30 mimics into zebrafish embryos resulted in suppression of dll4 and subsequent excessive sprouting of intersegmental vessels and reduction in dorsal aorta diameter. Use of a target protector against the miR-30 site within the dll4 3'UTR up-regulated dll4 and synergized with Vegfa signaling knockdown to inhibit angiogenesis. Furthermore, restoration of miR-30b or miR-30c expression during Kaposi sarcoma herpesvirus (KSHV) infection attenuated viral induction of DLL4. Together these results demonstrate that the highly conserved molecular targeting of DLL4 by the miR-30 family regulates angiogenesis.

MicroRNA-10A* and MicroRNA-21 modulate endothelial progenitor cell senescence via suppressing high-mobility group A2

RATIONALE

Endothelial progenitor cells (EPCs) contribute to the regeneration of endothelium. Aging-associated senescence results in reduced number and function of EPCs, potentially contributing to increased cardiac risk, reduced angiogenic capacity, and impaired cardiac repair effectiveness. The mechanisms underlying EPC senescence are unknown. Increasing evidence supports the role of microRNAs in regulating cellular senescence.

OBJECTIVE

We aimed to determine whether microRNAs regulated EPC senescence and, if so, what the underlying mechanisms are.

METHODS AND RESULTS

To map the microRNA/gene expression signatures of EPC senescence, we performed microRNA profiling and microarray analysis in lineage-negative bone marrow cells from young and aged wild-type and apolipoprotein E-deficient mice. We identified 2 microRNAs, microRNA-10A* (miR-10A*), and miR-21, and their common target gene Hmga2 as critical regulators for EPC senescence. Overexpression of miR-10A* and miR-21 in young EPCs suppressed Hmga2 expression, caused EPC senescence, as evidenced by senescence-associated β-galactosidase upregulation, decreased self-renewal potential, increased p16(Ink4a)/p19(Arf) expression, and resulted in impaired EPC angiogenesis in vitro and in vivo, resembling EPCs derived from aged mice. In contrast, suppression of miR-10A* and miR-21 in aged EPCs increased Hmga2 expression, rejuvenated EPCs, resulting in decreased senescence-associated β-galactosidase expression, increased self-renewal potential, decreased p16(Ink4a)/p19(Arf) expression, and improved EPC angiogenesis in vitro and in vivo. Importantly, these phenotypic changes were rescued by miRNA-resistant Hmga2 cDNA overexpression.

CONCLUSIONS

miR-10A* and miR-21 regulate EPC senescence via suppressing Hmga2 expression and modulation of microRNAs may represent a potential therapeutic intervention in improving EPC-mediated angiogenesis and vascular repair.

MicroRNAs and fibrosis

PURPOSE OF REVIEW

MicroRNAs (miRNAs) are short noncoding RNAs that inhibit gene expression in plants and animals. miRNAs have emerged as key players in virtually all aspects of mammalian biology. Aberrant miRNA expression is observed in numerous human diseases such as diabetes, hypercholesterolemia, cancer, and tissue fibrosis. Therefore, approaches to correct miRNA expression represent the novel therapeutic strategies for these diseases.

RECENT FINDINGS

miRNAs are essential for kidney development and homeostasis. Aberrant miRNA expression is observed in the mouse models of kidney fibrosis. Three TGF-β-regulated miRNA families, miR-21, miR-200, and miR-29 have been shown to modulate renal fibrosis. miR-21, through a feed-forward loop, amplifies TGF-β signaling and promotes fibrosis. Conversely, miR-200 and miR-29 reduce fibrosis by inhibiting epithelial-to-mesenchymal transition and preventing the deposition of extracellular matrix, respectively. Inhibition of miR-21 expression or augmenting miR-29 expression prevents kidney fibrosis in mice.

SUMMARY

Aberrant miRNA expression perturbs signaling pathways that lead to progression of kidney fibrosis. Thus, miRNAs represent novel biomarkers and therapeutic targets in the treatment of kidney fibrosis.

Overexpression of miR-30b in the developing mouse mammary gland causes a lactation defect and delays involution

Background

MicroRNA (miRNA) are negative regulators of gene expression, capable of exerting pronounced influences upon the translation and stability of mRNA. They are potential regulators of normal mammary gland development and of the maintenance of mammary epithelial progenitor cells. This study was undertaken to determine the role of miR-30b on the establishment of a functional mouse mammary gland. miR-30b is a member of the miR-30 family, composed of 6 miRNA that are highly conserved in vertebrates. It has been suggested to play a role in the differentiation of several cell types.

Methodology/Principal Findings

The expression of miR-30b was found to be regulated during mammary gland development. Transgenic mice overexpressing miR-30b in mammary epithelial cells were used to investigate its role. During lactation, mammary histological analysis of the transgenic mice showed a reduction in the size of alveolar lumen, a defect of the lipid droplets and a growth defect of pups fed by transgenic females. Moreover some mammary epithelial differentiated structures persisted during involution, suggesting a delay in the process. The genes whose expression was affected by the overexpression of miR-30b were characterized by microarray analysis.

Conclusion/Significance

Our data suggests that miR-30b is important for the biology of the mammary gland and demonstrates that the deregulation of only one miRNA could affect lactation and involution.

MYBL2 haploinsufficiency increases susceptibility to age-related haematopoietic neoplasia

The haematopoietic system is prone to age-related disorders ranging from deficits in functional blood cells to the development of neoplastic states. Such neoplasms often involve recurrent cytogenetic abnormalities, among which a deletion in the long arm of chromosome 20 (del20q) is common in myeloid malignancies. The del20q minimum deleted region contains nine genes, including MYBL2, which encodes a key protein involved in the maintenance of genome integrity. Here, we show that mice expressing half the normal levels of Mybl2 (Mybl2^+/Δ) develop a variety of myeloid disorders upon ageing. These include myeloproliferative neoplasms, myelodysplasia (MDS) and myeloid leukaemia, mirroring the human conditions associated with del20q. Moreover, analysis of gene expression profiles from patients with MDS demonstrated reduced levels of MYBL2, regardless of del20q status and demonstrated a strong correlation between low levels of MYBL2 RNA and reduced expression of a subset of genes related to DNA replication and checkpoint control pathways. Paralleling the human data, we found that these pathways are also disturbed in our Mybl2^+/Δ mice. This novel mouse model, therefore, represents a valuable tool for studying the initiation and progression of haematological malignancies during ageing, and may provide a platform for preclinical testing of therapeutic approaches.

Irinotecan induces senescence and apoptosis in colonic cells in vitro

Irinotecan (CPT-11) is topoisomerase I inhibitor used in the treatment of disseminated colorectal cancer. In colon cancer cells it induces DNA damage which leads to cytotoxicity with ensuing apoptosis or premature senescence. Despite its clinical use and efficiency in malignant colonocytes, its effects in normal colonic cells are relatively underexplored. In this work we report that CPT-11 induces dose-dependent cytotoxicity which results in apoptosis and premature senescence whose occurrence nevertheless varies in relation to the type of exposed cells. In normal colonic epithelial cells (NCM) the prevailing type of response is apoptosis whereas in normal colonic fibroblasts (NCF) it is premature senescence. Further analyses showed that CPT-11 induced in both types of cells DNA damage and activated stress response pathways including p53 and p16 but with varying activity of stress kinase p38 and selected stress-associated microRNAs. Epithelial cells upregulated the expression of p53, which was subsequently specifically phosphorylated, massively activated p38 and initiated mitochondrial, caspase-dependent apoptosis. These events occurred in the presence of moderately increased expression of miR-34a only. Conversely, in colonic fibroblasts p38 was only moderately activated, p53 as well as p16 expressions were upregulated in the presence of increased expression of miR-34a, miR-128a and miR-449a. Caspase-dependent apoptosis was found only in a minority of treated cells and the premature senescence phenotype was prevailing. Specific inhibition further proved that p53-dependent as well as independent mechanisms might be responsible for these cell type-specific differences.

Compromised autophagy by MIR30B benefits the intracellular survival of Helicobacter pylori

Helicobacter pylori evade immune responses and achieve persistent colonization in the stomach. However, the mechanism by which H. pylori infections persist is not clear. In this study, we showed that MIR30B is upregulated during H. pylori infection of an AGS cell line and human gastric tissues. Upregulation of MIR30B benefited bacterial replication by compromising the process of autophagy during the H. pylori infection. As a potential mechanistic explanation for this observation, we demonstrate that MIR30B directly targets ATG12 and BECN1, which are important proteins involved in autophagy. These results suggest that compromise of autophagy by MIR30B allows intracellular H. pylori to evade autophagic clearance, thereby contributing to the persistence of H. pylori infections.

The expression of microRNA and microRNA clusters in the aging heart

BACKGROUND

The microRNAs have been implicated in the process of cardiac development, cardiac hypertrophy, and heart failure. However, the impact of adult aging on cardiac expression of miRNA clusters, as well as both miRNA guide (miR) and passenger (miR*) strands has not been well established.

METHODS/RESULTS

We explored the expression profile of both miR and miR* in the hearts of young adult versus old mice. We found that 65 miRNAs were differentially expressed in the old versus young adult hearts; approximately half of them were clustered miRNAs that were distributed in 11 miRNA clusters. Each miRNA cluster contained from 2 to as many as 71 miRNA genes. The majority of the clusters displayed similar expression, with most cluster members within a cluster being either increased or decreased together, suggesting that most clusters are likely to be regulated by a common signaling mechanism and that the combined expression of multiple miRNA genes in a cluster could pose an impact on a broad range of targets during aging. We also found age-related changes in the expression of miR*s. The expression of both miR and miR* correlated with that of pri-miRNA transcript over the time course from development and maturation through adult aging. Age-related changes in the expression of Ago1 and Ago2 proteins in the heart were also observed. Transfection assay revealed that both Ago1 and Ago2 synergistically induced miR-21 and miR-21* when the mir-21 plasmid was co-transfected with either.

CONCLUSION

The data revealed age-related changes in the expression of pri-miRNA transcript, Argonaut proteins and both miR and miR* strands. The major changes occurred later in life, from middle to old age. It is likely that the expression of miR and miR* is regulated by both pri-miRNA transcription as well as Ago1 and Ago2 proteins during adult aging.

Age-dependent regulation of tumor-related microRNAs in the brain of the annual fish Nothobranchius furzeri

MicroRNAs are regulators of gene expression. We used miRNA-seq by the Illumina platform to quantify and compare the temporal miRNA expression profiles in the brain of a short-lived (GRZ) and a longer-lived strain (MZM) of the annual fish Nothobranchius furzeri. We used fuzzy-c-means clustering to group miRNAs with similar profiles. In MZM, we found tumor suppressors with known negative interactions with MYC and/or positive interactions with TP53 among up-regulated miRNAs (e.g. miR-23a, miR-26a/b, miR-29a/b and miR-101a) in aged animals. Conversely, we found oncogenes which are MYC targets among down-regulated miRNAs (miR-7a, members of miR cluster 17∼92). These latter were previously shown to be regulated in human replicative aging. In addition, three regulated miRNAs (miR-181c, miR-29a and miR-338) are known to be age-regulated and to globally contribute to regulation of their targets in the human brain. Therefore, there appears to be a degree of evolutionarily conservation in age-dependent miRNA expression between humans and N. furzeri. GRZ showed specific regulation of some miRNAs, notably a marked up-regulation of miR-124, a miRNA important for neuronal differentiation. The two strains differ in their miRNA expression profiles already at sexual maturity. Short lifespan in GRZ could therefore be--at least partially--due to dysregulated miRNA expression.

MicroRNA-203 regulates caveolin-1 in breast tissue during caloric restriction

Caloric restriction has been shown to increase lifespan in several organisms and to delay onset of age-related diseases. The transcriptional response to caloric restriction has been studied for mRNAs, while the microRNA signature following caloric restriction remains unexplored. Here, we characterize the microRNA expression in mouse breast tissue before and after caloric restriction, reporting several changes in the microRNA expression profile. In particular, miR-203 is found to be highly induced by caloric restriction, and we demonstrate that caveolin-1 as well as p63 are direct targets of miR-203 in vivo during caloric restriction. Using tissue culture models, we suggest that this regulation is important in both mouse and human. In conclusion, we show that the microRNA response induced by caloric restriction can regulate important factors in processes such as longevity and aging and is an integral and important component of the cellular response to caloric restriction.

MicroRNAs in autophagy and their emerging roles in crosstalk with apoptosis

Macroautophagy (hereafter referred to as autophagy) is an evolutionarily conserved self-degradative process, which involves the regular turnover of cellular components via sequestering damaged macromolecules and transporting them for lysosomal degradation. In the past few years, the scientific community has produced remarkable advances in our understanding of the genes that are involved in autophagy and of their profound effects on various diseases. Recently, a new class of noncoding RNAs, known as microRNAs (miRNAs), has been demonstrated to play crucial roles in diverse biological processes including development, cell differentiation and apoptosis. Here, we review the current understanding about miRNAs focusing on their involvement in the autophagy process. Intriguingly, several confirmed targets of these autophagy-miRNAs are also important regulators in the crosstalk between autophagy and apoptosis. Furthermore, transcripts involved in autophagy and apoptosis may indirectly modulate each other by competing for common miRNA binding sites. Thus, miRNAs potentially work as molecular switches between these two intimately connected processes and contribute to the cell fate decision.