Life Sciences Commons^™

Integrated Transcriptome Analysis Reveals Mirna-Mrna Crosstalk In Laryngeal Squamous Cell Carcinoma., Yang Zhang, Yong Chen, Jinhai Yu, Guiming Liu, Zhigang Huang

Yong Chen

Next generation sequencing (NGS) has proven to be a powerful tool in delineating myriads of molecular subtypes of cancer, as well as in revealing accumulation of genomic mutations throughout cancer progression. Whole genome microRNA (miRNA) and mRNA expression profiles were obtained from patients with laryngeal squamous cell carcinoma (LSCC) using deep sequencing technology, and were analyzed by utilizing integrative computational approaches. A large number of protein-coding and non-coding genes were detected to be differentially expressed, indicating a functional switch in LSCC cells. A total of 127 mutated genes were detected to be significantly associated with ectoderm and epidermis development. Eleven …

Biodistribution And Function Of Extracellular Mirna-155 In Mice, Shashi Bala, Timea Csak, Fatemeh Momen-Heravi, Dora Lippai, Karen Kodys, Donna Catalano, Abhishek Satishchandran, Victor R. Ambros, Gyongyi Szabo

Gyongyi Szabo

Circulating miRNAs can be found in extracellular vesicles (EV) and could be involved in intercellular communication. Here, we report the biodistribution of EV associated miR-155 using miR-155 KO mouse model. Administration of exosomes loaded with synthetic miR-155 mimic into miR-155 KO mice resulted in a rapid accumulation and clearance of miR-155 in the plasma with subsequent distribution in the liver, adipose tissue, lung, muscle and kidney (highest to lowest, respectively). miR-155 expression was detected in isolated hepatocytes and liver mononuclear cells of recipient KO mice suggesting its cellular uptake. In vitro, exosome-mediated restoration of miR-155 in Kupffer cells from miR-155 …

Caenorhabditis Elegans Alg-1 Antimorphic Mutations Uncover Functions For Argonaute In Microrna Guide Strand Selection And Passenger Strand Disposal, Anna Y. Zinovyeva, Isana Veksler-Lublinsky, Ajay A. Vashisht, James A. Wohlschlegel, Victor R. Ambros

Victor R. Ambros

MicroRNAs are regulators of gene expression whose functions are critical for normal development and physiology. We have previously characterized mutations in a Caenorhabditis elegans microRNA-specific Argonaute ALG-1 (Argonaute-like gene) that are antimorphic [alg-1(anti)]. alg-1(anti) mutants have dramatically stronger microRNA-related phenotypes than animals with a complete loss of ALG-1. ALG-1(anti) miRISC (microRNA induced silencing complex) fails to undergo a functional transition from microRNA processing to target repression. To better understand this transition, we characterized the small RNA and protein populations associated with ALG-1(anti) complexes in vivo. We extensively characterized proteins associated with wild-type and mutant ALG-1 and found that the mutant …

Robust Distal Tip Cell Pathfinding In The Face Of Temperature Stress Is Ensured By Two Conserved Micrornas In Caenorhabditis Elegans, Samantha L. Burke, Molly Hammell, Victor R. Ambros

Victor R. Ambros

Biological robustness, the ability of an organism to maintain a steady-state output as genetic or environmental inputs change, is critical for proper development. MicroRNAs have been implicated in biological robustness mechanisms through their post-transcriptional regulation of genes and gene networks. Previous research has illustrated examples of microRNAs promoting robustness as part of feedback loops and genetic switches and by buffering noisy gene expression resulting from environmental and/or internal changes. Here we show that the evolutionarily conserved microRNAs mir-34 and mir-83 (homolog of mammalian mir-29) contribute to the robust migration pattern of the distal tip cells in Caenorhabditis elegans by specifically …

Biodistribution And Function Of Extracellular Mirna-155 In Mice, Shashi Bala, Timea Csak, Fatemeh Momen-Heravi, Dora Lippai, Karen Kodys, Donna Catalano, Abhishek Satishchandran, Victor R. Ambros, Gyongyi Szabo

Victor R. Ambros

Circulating miRNAs can be found in extracellular vesicles (EV) and could be involved in intercellular communication. Here, we report the biodistribution of EV associated miR-155 using miR-155 KO mouse model. Administration of exosomes loaded with synthetic miR-155 mimic into miR-155 KO mice resulted in a rapid accumulation and clearance of miR-155 in the plasma with subsequent distribution in the liver, adipose tissue, lung, muscle and kidney (highest to lowest, respectively). miR-155 expression was detected in isolated hepatocytes and liver mononuclear cells of recipient KO mice suggesting its cellular uptake. In vitro, exosome-mediated restoration of miR-155 in Kupffer cells from miR-155 …

Inhibiting Mirna In Caenorhabditis Elegans Using A Potent And Selective Antisense Reagent, Genhua Zheng, Victor R. Ambros, Wen-Hong Li

Victor R. Ambros

BACKGROUND: Antisense reagents can serve as efficient and versatile tools for studying gene function by inhibiting nucleic acids in vivo. Antisense reagents have particular utility for the experimental manipulation of the activity of microRNAs (miRNAs), which are involved in the regulation of diverse developmental and physiological pathways in animals. Even in traditional genetic systems, such as the nematode Caenorhabditis elegans, antisense reagents can provide experimental strategies complementary to mutational approaches. Presently no antisense reagents are available for inhibiting miRNAs in the nematode C. elegans. RESULTS: We have developed a new class of fluorescently labelled antisense reagents to inhibit miRNAs in …

Mutations In Conserved Residues Of The C. Elegans Microrna Argonaute Alg-1 Identify Separable Functions In Alg-1 Mirisc Loading And Target Repression, Anna Y. Zinovyeva, Samir Bouasker, Martin J. Simard, Christopher M. Hammell, Victor R. Ambros

Victor R. Ambros

microRNAs function in diverse developmental and physiological processes by regulating target gene expression at the post-transcriptional level. ALG-1 is one of two Caenorhabditis elegans Argonautes (ALG-1 and ALG-2) that together are essential for microRNA biogenesis and function. Here, we report the identification of novel antimorphic (anti) alleles of ALG-1 as suppressors of lin-28(lf) precocious developmental phenotypes. The alg-1(anti) mutations broadly impair the function of many microRNAs and cause dosage-dependent phenotypes that are more severe than the complete loss of ALG-1. ALG-1(anti) mutant proteins are competent for promoting Dicer cleavage of microRNA precursors and for associating with and stabilizing microRNAs. However, …

Circulating Micrornas Are Associated With Paroxysmal Or Persistent Atrial Fibrillation, David D. Mcmanus, Jeanine Ward, Amir Y. Shaikh, Khushleen Jaggi, Victor R. Ambros, Jane Freedman, John F. Keaney Jr.

Victor R. Ambros

Introduction: Novel methods of identifying individuals at risk for atrial fibrillation (AF) are needed. MicroRNAs (MiRNAs) regulate gene expression in a number of cardiovascular diseases, including AF. It is unknown, however, if key circulating, cardiac-specific miRNAs differ between individuals with paroxysmal or persistent AF and those in sinus rhythm. Methods: 17 individuals with a history of AF were recruited prior to catheter ablation. 24 hospitalized patients in normal sinus rhythm and no history of AF comprised the control group. 94 plasma miRNAs were selected based on a priori associations with processes implicated in AF for evaluation using the TaqMan miRNA …

Caenorhabditis Elegans Micrornas Of The Let-7 Family Act In Innate Immune Response Circuits And Confer Robust Developmental Timing Against Pathogen Stress, Zhiji Ren, Victor R. Ambros

Victor R. Ambros

Animals maintain their developmental robustness against natural stresses through numerous regulatory mechanisms, including the posttranscriptional regulation of gene expression by microRNAs (miRNAs). Caenorhabditis elegans miRNAs of the let-7 family (let-7-Fam) function semiredundantly to confer robust stage specificity of cell fates in the hypodermal seam cell lineages. Here, we show reciprocal regulatory interactions between let-7-Fam miRNAs and the innate immune response pathway in C. elegans. Upon infection of C. elegans larvae with the opportunistic human pathogen Pseudomonas aeruginosa, the developmental timing defects of certain let-7-Fam miRNA mutants are enhanced. This enhancement is mediated by the p38 MAPK innate immune pathway acting …

Drosophila Let-7 Microrna Is Required For Remodeling Of The Neuromusculature During Metamorphosis, Nicholas S. Sokol, Peizhang Xu, Yuh-Nung Jan, Victor R. Ambros

Victor R. Ambros

The Drosophila let-7-Complex (let-7-C) is a polycistronic locus encoding three ancient microRNAs: let-7, miR-100, and fly lin-4 (miR-125). We find that the let-7-C locus is principally expressed in the pupal and adult neuromusculature. let-7-C knockout flies appear normal externally but display defects in adult behaviors (e.g., flight, motility, and fertility) as well as clear juvenile features in their neuromusculature. We find that the function of let-7-C to ensure the appropriate remodeling of the abdominal neuromusculature during the larval-to-adult transition is carried out predominantly by let-7 alone. This heterochronic role of let-7 is likely just one of the ways in which …

Effect Of Life History On Microrna Expression During C. Elegans Development, Xantha Karp, Molly Hammell, Maria C. Ow, Victor R. Ambros

Victor R. Ambros

Animals have evolved mechanisms to ensure the robustness of developmental outcomes to changing environments. MicroRNA expression may contribute to developmental robustness because microRNAs are key post-transcriptional regulators of developmental gene expression and can affect the expression of multiple target genes. Caenorhabditis elegans provides an excellent model to study developmental responses to environmental conditions. In favorable environments, C. elegans larvae develop rapidly and continuously through four larval stages. In contrast, in unfavorable conditions, larval development may be interrupted at either of two diapause stages: The L1 diapause occurs when embryos hatch in the absence of food, and the dauer diapause occurs …

The Flywch Transcription Factors Flh-1, Flh-2, And Flh-3 Repress Embryonic Expression Of Microrna Genes In C. Elegans, Maria C. Ow, Natalia Julia Martinez, Philip H. Olsen, Howard S. Silverman, M. Inmaculada Barrasa, Barbara Conradt, Albertha J. M. Walhout, Victor R. Ambros

Victor R. Ambros

MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression post-transcriptionally via antisense base-pairing. Although miRNAs are involved in a variety of important biological functions, little is known about their transcriptional regulation. Using yeast one-hybrid assays, we identified transcription factors with a FLYWCH Zn-finger DNA-binding domain that bind to the promoters of several Caenorhabditis elegans miRNA genes. The products of the flh-1 and flh-2 genes function redundantly to repress embryonic expression of lin-4, mir-48, and mir-241, miRNA genes that are normally expressed only post-embryonically. Although single mutations in either flh-1 or flh-2 genes result in a viable phenotype, double mutation …

A C. Elegans Genome-Scale Microrna Network Contains Composite Feedback Motifs With High Flux Capacity, Natalia Julia Martinez, Maria C. Ow, M. Inmaculada Barrasa, Molly Hammell, Reynaldo Sequerra, Lynn Doucette-Stamm, Frederick P. Roth, Victor R. Ambros, Albertha J. M. Walhout

Victor R. Ambros

MicroRNAs (miRNAs) and transcription factors (TFs) are primary metazoan gene regulators. Whereas much attention has focused on finding the targets of both miRNAs and TFs, the transcriptional networks that regulate miRNA expression remain largely unexplored. Here, we present the first genome-scale Caenorhabditis elegans miRNA regulatory network that contains experimentally mapped transcriptional TF --> miRNA interactions, as well as computationally predicted post-transcriptional miRNA --> TF interactions. We find that this integrated miRNA network contains 23 miRNA <--> TF composite feedback loops in which a TF that controls a miRNA is itself regulated by that same miRNA. By rigorous network randomizations, we show …

Most Caenorhabditis Elegans Micrornas Are Individually Not Essential For Development Or Viability, Eric A. Miska, Ezequiel Alvarez-Saavedra, Allison Abbott, Nelson C. Lau, Andrew B. Hellman, Shannon M. Mcgonagle, David P. Bartel, Victor R. Ambros, H. Robert Horvitz

Victor R. Ambros

MicroRNAs (miRNAs), a large class of short noncoding RNAs found in many plants and animals, often act to post-transcriptionally inhibit gene expression. We report the generation of deletion mutations in 87 miRNA genes in Caenorhabditis elegans, expanding the number of mutated miRNA genes to 95, or 83% of known C. elegans miRNAs. We find that the majority of miRNAs are not essential for the viability or development of C. elegans, and mutations in most miRNA genes do not result in grossly abnormal phenotypes. These observations are consistent with the hypothesis that there is significant functional redundancy among miRNAs or among …

Chronic Alcohol-Induced Microrna-155 Contributes To Neuroinflammation In A Tlr4-Dependent Manner In Mice, Dora Lippai, Shashi Bala, Timea Csak, Evelyn A. Kurt-Jones, Gyongyi Szabo

Gyongyi Szabo

INTRODUCTION: Alcohol-induced neuroinflammation is mediated by pro-inflammatory cytokines and chemokines including tumor necrosis factor-alpha (TNFalpha), monocyte chemotactic protein-1 (MCP1) and interleukin-1-beta (IL-1beta). Toll-like receptor-4 (TLR4) pathway induced nuclear factor-kappaB (NF-kappaB) activation is involved in the pathogenesis of alcohol-induced neuroinflammation. Inflammation is a highly regulated process. Recent studies suggest that microRNAs (miRNAs) play crucial role in fine tuning gene expression and miR-155 is a major regulator of inflammation in immune cells after TLR stimulation. AIM: To evaluate the role of miR-155 in the pathogenesis of alcohol-induced neuroinflammation. METHODS: Wild type (WT), miR-155- and TLR4-knockout (KO) mice received 5% ethanol-containing or isocaloric …

Circulating Microrna Profiles In Human Patients With Acetaminophen Hepatotoxicity Or Ischemic Hepatitis, Jeanine Ward, Chitra Kanchagar, Isana Veksler-Lublinsky, Rosalind C. Lee, Mitchell R. Mcgill, Hartmut Jaeschke, Steven C. Curry, Victor R. Ambros

Victor R. Ambros

We have identified, by quantitative real-time PCR, hundreds of miRNAs that are dramatically elevated in the plasma or serum of acetaminophen (APAP) overdose patients. Most of these circulating microRNAs decrease toward normal levels during treatment with N-acetyl cysteine (NAC). We identified a set of 11 miRNAs whose profiles and dynamics in the circulation during NAC treatment can discriminate APAP hepatotoxicity from ischemic hepatitis. The elevation of certain miRNAs can precede the dramatic rise in the standard biomarker, alanine aminotransferase (ALT), and these miRNAs also respond more rapidly than ALT to successful treatment. Our results suggest that miRNAs can serve as …

Preeclampsia And Micrornas, Eric J. Devor, Donna A. Santillan, Mark K. Santillan

Donna A. Santillan

Preeclampsia is a critical gestational condition that threatens the life of both mother and child. One of the most serious aspects of preeclampsia hampering both clinical management and scientific understanding is that there are, as yet, no early warning signs or risk markers. The discovery of microRNAs (miRNAs), tiny post-transcriptional regulators of gene expression, offers potentially fertile ground for developing such markers. The current state of knowledge about miRNAs in preeclampsia is presented along with information regarding miRNA detection in peripheral fluids that could lead to minimally invasive risk assessment.

Preeclampsia And Micrornas, Eric J. Devor, Donna A. Santillan, Mark K. Santillan

Mark K. Santillan

Preeclampsia is a critical gestational condition that threatens the life of both mother and child. One of the most serious aspects of preeclampsia hampering both clinical management and scientific understanding is that there are, as yet, no early warning signs or risk markers. The discovery of microRNAs (miRNAs), tiny post-transcriptional regulators of gene expression, offers potentially fertile ground for developing such markers. The current state of knowledge about miRNAs in preeclampsia is presented along with information regarding miRNA detection in peripheral fluids that could lead to minimally invasive risk assessment.

Preeclampsia And Micrornas, Eric J. Devor, Donna A. Santillan, Mark K. Santillan

Eric J Devor

Preeclampsia is a critical gestational condition that threatens the life of both mother and child. One of the most serious aspects of preeclampsia hampering both clinical management and scientific understanding is that there are, as yet, no early warning signs or risk markers. The discovery of microRNAs (miRNAs), tiny post-transcriptional regulators of gene expression, offers potentially fertile ground for developing such markers. The current state of knowledge about miRNAs in preeclampsia is presented along with information regarding miRNA detection in peripheral fluids that could lead to minimally invasive risk assessment.

Microrna Signature In Alcoholic Liver Disease, Shashi Bala, Gyongyi Szabo

Gyongyi Szabo

Alcoholic liver disease (ALD) is a major global health problem. Chronic alcohol use results in inflammation and fatty liver, and in some cases, it leads to fibrosis and cirrhosis or hepatocellular carcinoma. Increased proinflammatory cytokines, particularly TNF alpha, play a central role in the pathogenesis of ALD. TNF alpha is tightly regulated at transcriptional and posttranscriptional levels. Recently, microRNAs (miRNAs) have been shown to modulate gene functions. The role of miRNAs in ALD is getting attention, and recent studies suggest that alcohol modulates miRNAs. Recently, we showed that alcohol induces miR-155 expression both in vitro (RAW 264.7 macrophage) and in …

Plasma Microrna Profiles Distinguish Lethal Injury In Acetaminophen Toxicity: A Research Study, Jeanine Ward, Shashi Bala, Jan Petrasek, Gyongyi Szabo

Gyongyi Szabo

AIM: To investigate plasma microRNA (miRNA) profiles indicative of hepatotoxicity in the setting of lethal acetaminophen (APAP) toxicity in mice. METHODS: Using plasma from APAP poisoned mice, either lethally (500 mg/kg) or sublethally (150 mg/kg) dosed, we screened commercially available murine microRNA libraries (SABiosciences, Qiagen Sciences, MD) to evaluate for unique miRNA profiles between these two dosing parameters. RESULTS: We distinguished numerous, unique plasma miRNAs both up- and downregulated in lethally compared to sublethally dosed mice. Of note, many of the greatest up- and downregulated miRNAs, namely 574-5 p, 466 g, 466 f-3p, 375, 29 c, and 148 a, have …

Increased Microrna-155 Expression In The Serum And Peripheral Monocytes In Chronic Hcv Infection, Shashi Bala, Yaphet Tilahun, Odette Taha, Hawau Alao, Karen Kodys, Donna Catalano, Gyongyi Szabo

Gyongyi Szabo

BACKGROUND: Hepatitis C Virus (HCV), a single stranded RNA virus, affects millions of people worldwide and leads to chronic infection characterized by chronic inflammation in the liver and in peripheral immune cells. Chronic liver inflammation leads to progressive liver damage. MicroRNAs (miRNA) regulate inflammation (miR-155, -146a and -125b) as well as hepatocyte function (miR-122). METHODS: Here we hypothesized that microRNAs are dysregulated in chronic HCV infection. We examined miRNAs in the circulation and in peripheral monocytes of patients with chronic HCV infection to evaluate if specific miRNA expression correlated with HCV infection. RESULTS: We found that monocytes from chronic HCV …

The Path To Microrna Therapeutics In Psychiatric And Neurodegenerative Disorders, Anthony W. S. Chan, Jannet Kocerha

Jannet Kocerha

The microRNA (miRNA) class of non-coding RNAs exhibit a diverse range of regulatory roles in neuronal functions that are conserved from lower vertebrates to primates. Disruption of miRNA expression has compellingly been linked to pathogenesis in neuropsychiatric and neurodegenerative disorders, such as schizophrenia, Alzheimer’s disease, and autism. The list of transcript targets governed by a single miRNA provide a molecular paradigm applicable for therapeutic intervention. Indeed, reports have shown that specific manipulation of a miRNA in cell or animal models can significantly alter phenotypes linked with neurological disease. Here, we review how a diverse range of biological systems, including Drosophila, …

Microrna-Regulated, Systemically Delivered Raav9: A Step Closer To Cns-Restricted Transgene Expression, Jun Xie, Qing Xie, Hongwei Zhang, Stefan L. Ameres, Jui-Hung Hung, Qin Su, Ran He, Xin Mu, Seemin Seher Ahmed, Soyeon Park, Hiroki Kato, Chengjian Li, Christian Mueller, Craig C. Mello, Zhiping Weng, Terence R. Flotte, Phillip D. Zamore, Guangping Gao

Christian Mueller

Recombinant adeno-associated viruses (rAAVs) that can cross the blood-brain-barrier and achieve efficient and stable transvascular gene transfer to the central nervous system (CNS) hold significant promise for treating CNS disorders. However, following intravascular delivery, these vectors also target liver, heart, skeletal muscle, and other tissues, which may cause untoward effects. To circumvent this, we used tissue-specific, endogenous microRNAs (miRNAs) to repress rAAV expression outside the CNS, by engineering perfectly complementary miRNA-binding sites into the rAAV9 genome. This approach allowed simultaneous multi-tissue regulation and CNS-directed stable transgene expression without detectably perturbing the endogenous miRNA pathway. Regulation of rAAV expression by miRNA …

Sustained Mirna-Mediated Knockdown Of Mutant Aat With Simultaneous Augmentation Of Wild-Type Aat Has Minimal Effect On Global Liver Mirna Profiles, Christian Mueller, Qiushi Tang, Alisha Gruntman, Keith S. Blomenkamp, Jeffrey H. Teckman, Lina Song, Phillip D. Zamore, Terence R. Flotte

Christian Mueller

Alpha-1 antitrypsin (AAT) deficiency can exhibit two pathologic states: a lung disease that is primarily due to the loss of AAT's antiprotease function, and a liver disease resulting from a toxic gain-of-function of the PiZ-AAT (Z-AAT) mutant protein. We have developed several recombinant adeno-associated virus (rAAV) vectors that incorporate microRNA (miRNA) sequences targeting the AAT gene while also driving the expression of miRNA-resistant wild-type AAT-PiM (M-AAT) gene, thus achieving concomitant Z-AAT knockdown in the liver and increased expression of M-AAT. Transgenic mice expressing the human PiZ allele treated with dual-function rAAV9 vectors showed that serum PiZ was stably and persistently …

Detecting Microrna Activity From Gene Expression Data, Stephen F. Madden, Susan B. Carpenter, Ian B. Jeffery, Harry Bjorkbacka, Katherine A. Fitzgerald, Luke A. J. O'Neill, Desmond G. Higgins

Katherine A. Fitzgerald

BACKGROUND: MicroRNAs (miRNAs) are non-coding RNAs that regulate gene expression by binding to the messenger RNA (mRNA) of protein coding genes. They control gene expression by either inhibiting translation or inducing mRNA degradation. A number of computational techniques have been developed to identify the targets of miRNAs. In this study we used predicted miRNA-gene interactions to analyse mRNA gene expression microarray data to predict miRNAs associated with particular diseases or conditions.

RESULTS: Here we combine correspondence analysis, between group analysis and co-inertia analysis (CIA) to determine which miRNAs are associated with differences in gene expression levels in microarray data sets. …

Emerging Role Of Micrornas In Liver Diseases, Shashi Bala, Miguel Marcos, Gyongyi Szabo

Gyongyi Szabo

MicroRNAs are a class of small non-coding RNAs that are found in plants, animals, and some viruses. They modulate the gene function at the post-transcriptional level and act as a fine tuner of various processes, such as development, proliferation, cell signaling, and apoptosis. They are associated with different types and stages of cancer. Recent studies have shown the involvement of microRNAs in liver diseases caused by various factors, such as Hepatitis C, Hepatitis B, metabolic disorders, and by drug abuse. This review highlights the role of microRNAs in liver diseases and their potential use as therapeutic molecules.

A Feedback Circuit Involving Let-7-Family Mirnas And Daf-12 Integrates Environmental Signals And Developmental Timing In Caenorhabditis Elegans, Christopher M. Hammell, Xantha Karp, Victor R. Ambros

Victor R. Ambros

Animal development is remarkably robust; cell fates are specified with spatial and temporal precision despite physiological and environmental contingencies. Favorable conditions cause Caenorhabditis elegans to develop rapidly through four larval stages (L1-L4) to the reproductive adult. In unfavorable conditions, L2 larvae can enter the developmentally quiescent, stress-resistant dauer larva stage, enabling them to survive for prolonged periods before completing development. A specific progression of cell division and differentiation events occurs with fidelity during the larval stages, regardless of whether an animal undergoes continuous or dauer-interrupted development. The temporal patterning of developmental events is controlled by the heterochronic genes, whose products …

The Small Rna Repertoire Of Dictyostelium Discoideum And Its Regulation By Components Of The Rnai Pathway., Wolfgang Nellen, Andrea Hinas, Johan Reimegard, E. Gerhart H. Wagner, Victor R. Ambros, Fredrik Soderbom

Victor R. Ambros

Small RNAs play crucial roles in regulation of gene expression in many eukaryotes. Here, we report the cloning and characterization of 18-26 nt RNAs in the social amoeba Dictyostelium discoideum. This survey uncovered developmentally regulated microRNA candidates whose biogenesis, at least in one case, is dependent on a Dicer homolog, DrnB. Furthermore, we identified a large number of 21 nt RNAs originating from the DIRS-1 retrotransposon, clusters of which have been suggested to constitute centromeres. Small RNAs from another retrotransposon, Skipper, were significantly up-regulated in strains depleted of the second Dicer-like protein, DrnA, and a putative RNA-dependent RNA polymerase, RrpC. …

Mesodermally Expressed Drosophila Microrna-1 Is Regulated By Twist And Is Required In Muscles During Larval Growth., Nicholas S. Sokol, Victor R. Ambros

Victor R. Ambros

Although hundreds of evolutionarily conserved microRNAs have been discovered, the functions of most remain unknown. Here, we describe the embryonic spatiotemporal expression profile, transcriptional regulation, and loss-of-function phenotype of Drosophila miR-1 (DmiR-1). DmiR-1 RNA is highly expressed throughout the mesoderm of early embryos and subsequently in somatic, visceral, and pharyngeal muscles, and the dorsal vessel. The expression of DmiR-1 is controlled by the Twist and Mef2 transcription factors. DmiR-1KO mutants, generated using ends-in gene targeting, die as small, immobilized second instar larvae with severely deformed musculature. This lethality is rescued when a DmiR-1 transgene is expressed specifically in the mesoderm …