Study On The Unconventional Function Of MiRNA

MicroRNAs(miRNAs)are small(?22 nucleotides)non-coding RNA molecules that act as endogenous suppressors of gene expression by binding to the 3'-untranslated region(3'-UTR)of target mRNAs to induce translational repression or mRNA cleavage.miRNAs are one of the most abundant classes of regulators,and play an important role in various physiological and pathological processesMicroRNAs(miRNAs)have emerged as a major regulator of the initiation and progression of human cancers,including breast cancer.However,the cooperative effects and transcriptional regulation of multiple miRNAs,especially miRNAs that are present in clusters,remain largely undiscovered.Here we showed that all members of the miR-23?27?24 clusters are upregulated and function as oncogenes in breast cancer and simultaneously target HIC1.Furthermore,we found that HIC1 functions as a transcriptional repressor to negatively control the expression of miR-23?27?24 clusters and forms a double-negative feedback loop.This feedback regulatory pathway is important because overexpression of miR-23?27?24 clusters can remarkably accelerate tumor growth,while restoration of HICl significantly blocks tumor growth in vivo.A mathematical model was created to quantitatively illustrate the regulatory circuit.Our finding highlights the cooperative effects of miRNAs in a cluster and adds another layer of complexity to the miRNA regulatory network.This study may also provide insight into the molecular mechanisms of breast cancer progression.The discovery of extracellular miRNAs has opened a new field in miRNA research.Extracellular miRNAs can be divided into extracellular vesicle(EV)-dependent or EV-free miRNAs.EV-dependent extracellular miRNAs have been widely reported to play an important role in genetic information transfer and intercellular communication,whereas the biological functions and regulatory mechanism of EV-free extracellular miRNAs are largely unknown.Hepatic injury is often accompanied by pulmonary inflammation and tissue damage,but the underneath mechanism is not fully elucidated.Here we identify hepatic miR-122 as a culprit of pulmonary inflammation induced by various liver injuries.Analyses of acute and chronic liver injury mouse models confirm that liver dysfunction can cause pulmonary inflammation and tissue damage.Injured livers release large amounts of miR-122 in a microvesicle-independent manner into the circulation compared to normal livers.Circulating miR-122 is then preferentially transported to mouse lungs and taken up by alveolar macrophages,in which it binds toll-like receptor 7(TLR7)and activates inflammatory responses.Depleting plasma miR-122 largely abolishes liver injury-induced pulmonary inflammation and tissue damage.Furthermore,alveolar macrophage activation by miR-122 is blocked by mutating the TLR7-binding UG-rich sequence on miR-122 or knocking out macrophage TLR7.Our findings reveal a novel causative role of hepatic miR-122 in liver injury-induced pulmonary dysfunction and elucidate the roles of MV-free circulating miRNAs in intercellular communicationIntergenerational epigenetic inheritance is the transmittance of information from one generation of an organism to the next(e.g.,parent-child transmittance)that affects the traits of offspring without alteration of the primary structure of DNA(i.e.,the sequence of nucleotides).Such transmission is proposed to occur mostly through alterations in the epigenomes of germ cells and is dependent on parental environment exposure or maternal in utero environment.However,the fundamental questions regarding the potential mechanisms responsible for the described phenomena remain to be elucidated.Depression,as a classic psychiatric disorder induced by both genetic and environmental effects,meets the basic characteristics of intergenerational inheritance.However,little is known about if depression in offspring can result from the father through a mechanism of intergenerational inheritance.Recent studies have shown that sperm miRNAs contribute to intergenerational inheritance of an acquired disorder,but the mechanism remains to be fully understood.In this study,by using behavioral techniques,immunostaining,patch clamp recording,real time RT-PCR and western blot,we demonstrated that depression in father could affect the psychic state and neurobehavioral function of their offspring and increase depressive susceptibility of their offspring.We further performed high-throughput Solexa sequencing using sperm RNA from normal or depressive mice.Interestingly,we saw striking differences between the miRNAs found in the normal and depressive mice.To assess whether sperm miRNAs can induce intergenerational phenotypes,we purified small fragments of RNA(<200nt)from the sperm of both normal and depressive mice and injected them into normal zygotes.By using behavioral techniques,immunostaining,patch clamp recording,real time RT-PCR and western blot,we found that the offspring from depression group showed a higher depressive susceptibility.We next synthesized a combination of antisense of the most highly differentially expressed miRNAs in the sperm.Interestingly,injecting synthetic miRNAs antisense with total RNAs from the sperm of depressive mice into normal zygotes could restore the function of total RNAs from the sperm of depressive mice.Finally,we use the single cell sequencing,bioinformatics analysis and in vitro experiments to elucidate the regulatory network between differentially expressed miRNAs and their target genes in the early embryo and brain.Overall,our project may provide important information for understanding the influence of parental environment on human health.A better understanding of intergenerational epigenetic inheritance and the consequences of such acquired changes on individuals will likely provide insight into how gene-environment interactions shape development and physiological functions.Taken together,our results show that miRNAs are important regulator in a wide array of cellular and developmental processes and it is crucial to study miRNA in different levels for further exploring the unconventional biological function of miRNA.