The C. elegans microRNA mir-71 acts in neurons to promote germline-mediated longevity through regulation of DAF-16/FOXO

Exosomal MiRNA Transfer between Retinal Microglia and RPE

The retinal pigment epithelium (RPE), the outermost layer of the retina, provides essential support to both the neural retina and choroid. Additionally, the RPE is highly active in modulating functions of immune cells such as microglia, which migrate to the subretinal compartment during aging and age-related degeneration. Recently, studies have highlighted the important roles of microRNA (miRNA) in the coordination of general tissue maintenance as well as in chronic inflammatory conditions. In this study, we analyzed the miRNA profiles in extracellular vesicles (EVs) released by the RPE, and identified and validated miRNA species whose expression levels showed age-dependent changes in the EVs. Using co-culture of RPE and retinal microglia, we further demonstrated that miR-21 was transferred between the two types of cells, and the increased miR-21 in microglia influenced the expression of genes downstream of the p53 pathway. These findings suggest that exosome-mediated miRNA transfer is a signaling mechanism that contributes to the regulation of microglia function in the aging retina.

MiDaf16-like and MiSkn1-like gene families are reliable targets to develop biotechnological tools for the control and management of Meloidogyne incognita

Meloidogyne incognita is a plant-parasitic root-knot nematode (RKN, PPN) responsible for causing damage to several crops worldwide. In Caenorhabditis elegans, the DAF-16 and SKN-1 transcription factors (TFs) orchestrate aging, longevity, and defense responses to several stresses. Here, we report that MiDaf16-like1 and MiSkn1-like1, which are orthologous to DAF-16 and SKN-1 in C. elegans, and some of their targets, are modulated in M. incognita J2 during oxidative stress or plant parasitism. We used RNAi technology for the stable production of siRNAs in planta to downregulate the MiDaf16-like1 and MiSkn1-like1 genes of M. incognita during host plant parasitism. Arabidopsis thaliana and Nicotiana tabacum overexpressing a hairpin-derived dsRNA targeting these genes individually (single-gene silencing) or simultaneously (double-gene silencing) were generated. T2 plants were challenged with M. incognita and the number of eggs, galls, and J2, and the nematode reproduction factor (NRF) were evaluated. Our data indicate that MiDaf16-like1, MiSkn1-like1 and some genes from their networks are modulated in M. incognita J2 during oxidative stress or plant parasitism. Transgenic A. thaliana and N. tabacum plants with single- or double-gene silencing showed significant reductions in the numbers of eggs, J2, and galls, and in NRF. Additionally, the double-gene silencing plants had the highest resistance level. Gene expression assays confirmed the downregulation of the MiDaf16-like1 and MiSkn1-like1 TFs and defense genes in their networks during nematode parasitism in the transgenic plants. All these findings demonstrate that these two TFs are potential targets for the development of biotechnological tools for nematode control and management in economically important crops.

Dynamic Changes in the Global Transcriptome and MicroRNAome Reveal Complex miRNA-mRNA Regulation in Early Stages of the Bi-Directional Development of Echinococcus granulosus Protoscoleces

Background

Cystic echinococcosis is a life-threatening disease caused by the larval stages of the dog tapeworm Echinococcus granulosus. Protoscoleces (PSCs) of this worm have the ability of bi-directional development to either larval cysts or strobilar adult worms. However, the molecular mechanisms underlying this development process are unknown.

Results

RNA and small RNAs sequencing was employed to characterize the gene and miRNA expression at 0–24 h and 7–14 days in the bi-directional development of PSCs. A total of 963 genes and 31 miRNAs were differentially expressed in the early development of PSCs to adult worms whereas 972 genes and 27 miRNAs were differentially expressed in the early development of PSCs to cysts. Pairwise comparison between the two developmental patterns showed that 172 genes and 15 miRNAs were differentially expressed at three time-points. Most of these genes were temporally changed at 24 h or 7 days. GO enrichment analysis revealed that the differentially expressed genes in early adult worm development are associated with nervous system development and carbohydrate metabolic process; whereas, the differentially expressed genes in early cystic development are associated with transmembrane transporter activity and nucleoside triphosphatase activity. In addition, miR-71 and miR-219 regulated genes are likely involved in oxidation reduction in adult worm development.

Conclusion

The early stages of bi-directional development in E. granulosus PSCs are controlled by miRNAs and genes likely associated with nervous system development and carbohydrate metabolic process. ATP-dependent transporter genes are associated with cystic development. These results may be important for exploring the mechanisms underlying early development in E. granulosus providing novel information that can be used to discover new therapeutics for controlling cystic echinococcosis.

Endogenous siRNAs promote proteostasis and longevity in germline-less Caenorhabditis elegans

How lifespan and the rate of aging are set is a key problem in biology. Small RNAs are conserved molecules that impact diverse biological processes through the control of gene expression. However, in contrast to miRNAs, the role of endo-siRNAs in aging remains unexplored. Here, by combining deep sequencing and genomic and genetic approaches in Caenorhabditis elegans, we reveal an unprecedented role for endo-siRNA molecules in the maintenance of proteostasis and lifespan extension in germline-less animals. Furthermore, we identify an endo-siRNA-regulated tyrosine phosphatase, which limits the longevity of germline-less animals by restricting the activity of the heat shock transcription factor HSF-1. Altogether, our findings point to endo-siRNAs as a link between germline removal and the HSF-1 proteostasis and longevity-promoting somatic pathway. This establishes a role for endo siRNAs in the aging process and identifies downstream genes and physiological processes that are regulated by the endo siRNAs to affect longevity.

DAF-16/FoxO in Caenorhabditis elegans and Its Role in Metabolic Remodeling

DAF-16, the only forkhead box transcription factors class O (FoxO) homolog in Caenorhabditis elegans, integrates signals from upstream pathways to elicit transcriptional changes in many genes involved in aging, development, stress, metabolism, and immunity. The major regulator of DAF-16 activity is the insulin/insulin-like growth factor 1 (IGF-1) signaling (IIS) pathway, reduction of which leads to lifespan extension in worms, flies, mice, and humans. In C. elegans daf-2 mutants, reduced IIS leads to a heterochronic activation of a dauer survival program during adulthood. This program includes elevated antioxidant defense and a metabolic shift toward accumulation of carbohydrates (i.e., trehalose and glycogen) and triglycerides, and activation of the glyoxylate shunt, which could allow fat-to-carbohydrate conversion. The longevity of daf-2 mutants seems to be partially supported by endogenous trehalose, a nonreducing disaccharide that mammals cannot synthesize, which points toward considerable differences in downstream mechanisms by which IIS regulates aging in distinct groups.

Regulatory Role of MicroRNAs in Brain Development and Function

MicroRNAs (miRNAs) are small non-coding RNA molecules of about 20-22 nucleotides. After their posttranscriptional maturation, miRNAs are loaded into the ribonucleoprotein complex RISC and modulate gene expression by binding to the 3' untranslated region of their target mRNAs through base-pairing, which in turn triggers mRNA degradation or translational inhibition. There is mounting evidence that miRNAs regulate various biological processes, including cell proliferation, differentiation, and apoptosis. Several studies have shown that miRNAs play an important role in neurogenesis and brain development.This review discusses recent progress on understanding the implication of precisely regulated miRNA expression in normal brain development and function. In addition, it reports known cases of dysregulation of miRNA expression and function implicated in the pathogenesis of neurodevelopmental disorders, craniofacial dysmorphic syndromes, neurodegenerative diseases, and psychiatric disorders. Current knowledge regarding the role of miRNAs in the brain in conjunction with the complex interplay between genetic and epigenetic factors are discussed.

circRNAs expressed in human peripheral blood are associated with human aging phenotypes, cellular senescence and mouse lifespan

Circular RNAs (circRNAs) are an emerging class of non-coding RNA molecules that are thought to regulate gene expression and human disease. Despite the observation that circRNAs are known to accumulate in older organisms and have been reported in cellular senescence, their role in aging remains relatively unexplored. Here, we have assessed circRNA expression in aging human blood and followed up age-associated circRNA in relation to human aging phenotypes, mammalian longevity as measured by mouse median strain lifespan and cellular senescence in four different primary human cell types. We found that circRNAs circDEF6, circEP300, circFOXO3 and circFNDC3B demonstrate associations with parental longevity or hand grip strength in 306 subjects from the InCHIANTI study of aging, and furthermore, circFOXO3 and circEP300 also demonstrate differential expression in one or more human senescent cell types. Finally, four circRNAs tested showed evidence of conservation in mouse. Expression levels of one of these, circPlekhm1, was nominally associated with lifespan. These data suggest that circRNA may represent a novel class of regulatory RNA involved in the determination of aging phenotypes, which may show future promise as both biomarkers and future therapeutic targets for age-related disease.

Interferon-β-induced miR-1 alleviates toxic protein accumulation by controlling autophagy

Appropriate regulation of autophagy is crucial for clearing toxic proteins from cells. Defective autophagy results in accumulation of toxic protein aggregates that detrimentally affect cellular function and organismal survival. Here, we report that the microRNA miR-1 regulates the autophagy pathway through conserved targeting of the orthologous Tre-2/Bub2/CDC16 (TBC) Rab GTPase-activating proteins TBC-7 and TBC1D15 in Caenorhabditis elegans and mammalian cells, respectively. Loss of miR-1 causes TBC-7/TBC1D15 overexpression, leading to a block on autophagy. Further, we found that the cytokine interferon-β (IFN-β) can induce miR-1 expression in mammalian cells, reducing TBC1D15 levels, and safeguarding against proteotoxic challenges. Therefore, this work provides a potential therapeutic strategy for protein aggregation disorders.

Protein quality control: from mechanism to disease : EMBO Workshop, Costa de la Calma (Mallorca), Spain, April 28 - May 03, 2019

The cellular protein quality control machinery with its central constituents of chaperones and proteases is vital to maintain protein homeostasis under physiological conditions and to protect against acute stress conditions. Imbalances in protein homeostasis also are keys to a plethora of genetic and acquired, often age-related, diseases as well as aging in general. At the EMBO Workshop, speakers covered all major aspects of cellular protein quality control, from basic mechanisms at the molecular, cellular, and organismal level to medical translation. In this report, the highlights of the meeting will be summarized.

Noncoding RNA Regulation of Dormant States in Evolutionarily Diverse Animals

Dormancy is evolutionarily widespread and can take many forms, including diapause, dauer formation, estivation, and hibernation. Each type of dormancy is characterized by distinct features; but accumulating evidence suggests that each is regulated by some common processes, often referred to as a common "toolkit" of regulatory mechanisms, that likely include noncoding RNAs that regulate gene expression. Noncoding RNAs, especially microRNAs, are well-known regulators of biological processes associated with numerous dormancy-related processes, including cell cycle progression, cell growth and proliferation, developmental timing, metabolism, and environmental stress tolerance. This review provides a summary of our current understanding of noncoding RNAs and their involvement in regulating dormancy.

Circ-Foxo3 is positively associated with the Foxo3 gene and leads to better prognosis of acute myeloid leukemia patients

Background

The Foxo3 gene, belonging to the forkhead family, is one of the classes of transcription factors characterized by a forkhead DNA-binding domain, which usually considered being a cancer suppressor gene. Circ-Foxo3 is a circular structure which connects the 3’end to the 5’end. Scholars detected that circ-Foxo3 could compete with Foxo3 for binding to some miRNAs.

Methods

In this study, we will test the expression of Foxo3 and circ-Foxo3 in de novo acute myeloid leukemia (AML) patients to explore the relationship between Foxo3 gene and circ-Foxo3. All the de novo AML samples and normal control samples was measured by real-time quantitative PCR. A receiver operating characteristic curve was conducted to differentiate AML patients from control people. Association of Foxo3 expression and overall survival was conducted by Kaplan-Meier survival analysis.

Results

We found that the expression of Foxo3 gene in de novo patients was significantly lower than control samples (P = 0.009). Meanwhile, circ-Foxo3 also expressed lower in de novo AML patients than in control samples (P = 0.040). In different classifications, this trend could be observed more remarkably. In non-M3 patients, the Foxo3 high patients’ survival time was longer than Foxo3 low patients (P = 0.002). Besides, in non-favorable risk groups, patients with low expression of Foxo3 had longer survival time than Foxo3 high patients (P = 0.004). Furthermore, in normal Karyotypic patients, the overall survival time of patients with high-expressed Foxo3 was significantly longer than those with low expression (P = 0.034). Besides, Pearson analysis was also conducted between these two genes in AML patients. Results revealed that they were positively correlated (R = 0.63, P < 0.001).

Conclusion

In conclusion, we found that low expression of circ-Foxo3 and Foxo3 were frequent in AML patients, and patients with high expression of Foxo3 often had a trend of better prognosis.

High-throughput identification of microRNAs in Taenia hydatigena, a cestode threatening livestock breeding industry

Infection of Cysticercus tenuicollis, the larval stage of Taenia hydatigena, is extensively found in sheep and pigs and jeopardizes the breeding and meat industry. miRNAs are a subclass of small noncoding regulatory RNAs and closely associated with the pathogenesis and biology of parasites. Here, using HiSeq sequencing we identified 49 known and 2 potential novel miRNAs in C. tenuicollis, of which both thy-miR-71 and -87 were predominant. Using RT-qPCR, 6 selected miRNAs were validated, and thy-miR-71 and -miR-87 were confirmed to be highly expressed, with the copy number of approximately 82,340 ± 2079 and 19,580 ± 609 per 1 ng total RNA, respectively. Similar to other cestodes, T. hydatigena was predicted to have two conserved miRNA clusters thy-miR-71/2c/2b and thy-miR-4989/277, and three members of the former were confirmed to reside sequentially within the genomic region of 253 bp by PCR. The current data provide us a valuable resource for further studies of a role of miRNAs in T. hydatigena biology and infection.

CBP-1 Acts in GABAergic Neurons to Double Life Span in Axenically Cultured Caenorhabditis elegans

When cultured in axenic medium, Caenorhabditis elegans shows the largest life-span extension compared with other dietary restriction regimens. However, the underlying molecular mechanism still remains elusive. The gene cbp-1, encoding the worm ortholog of p300/CBP (CREB-binding protein), is one of the very few key genes known to be essential for life span doubling under axenic dietary restriction (ADR). By using tissue-specific RNAi, we found that cbp-1 expression in the germline is essential for fertility, whereas this gene functions specifically in the GABAergic neurons to support the full life span-doubling effect of ADR. Surprisingly, GABA itself is not required for ADR-induced longevity, suggesting a role of neuropeptide signaling. In addition, chemotaxis assays illustrate that neuronal inactivation of CBP-1 affects the animals' food sensing behavior. Together, our results show that the strong life-span extension in axenic medium is under strict control of GABAergic neurons and may be linked to food sensing.

MicroRNAs as modulators of longevity and the aging process

MicroRNAs (miRNAs) are short, non-coding RNAs that post-transcriptionally repress translation or induce mRNA degradation of target transcripts through sequence-specific binding. miRNAs target hundreds of transcripts to regulate diverse biological pathways and processes, including aging. Many microRNAs are differentially expressed during aging, generating interest in their use as aging biomarkers and roles as regulators of the aging process. In the invertebrates Caenorhabditis elegans and Drosophila, a number of miRNAs have been found to both positive and negatively modulate longevity through canonical aging pathways. Recent studies have also shown that miRNAs regulate age-associated processes and pathologies in a diverse array of mammalian tissues, including brain, heart, bone, and muscle. The review will present an overview of these studies, highlighting the role of individual miRNAs as biomarkers of aging and regulators of longevity and tissue-specific aging processes.

Neuronal Small RNAs Control Behavior Transgenerationally

It is unknown whether the activity of the nervous system can be inherited. In Caenorhabditis elegans nematodes, parental responses can transmit heritable small RNAs that regulate gene expression transgenerationally. In this study, we show that a neuronal process can impact the next generations. Neurons-specific synthesis of RDE-4-dependent small RNAs regulates germline amplified endogenous small interfering RNAs (siRNAs) and germline gene expression for multiple generations. Further, the production of small RNAs in neurons controls the chemotaxis behavior of the progeny for at least three generations via the germline Argonaute HRDE-1. Among the targets of these small RNAs, we identified the conserved gene saeg-2, which is transgenerationally downregulated in the germline. Silencing of saeg-2 following neuronal small RNA biogenesis is required for chemotaxis under stress. Thus, we propose a small-RNA-based mechanism for communication of neuronal processes transgenerationally.

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C. elegans neuronal small RNAs are characterized by RNA sequencing

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RDE-4-dependent neuronal endogenous small RNAs communicate with the germline

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Germline HRDE-1 mediates transgenerational regulation by neuronal small RNAs

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Neuronal small RNAs regulate germline genes to control behavior transgenerationally

Olfaction regulates organismal proteostasis and longevity via microRNA-dependent signaling

The maintenance of proteostasis is crucial for any organism to survive and reproduce in an ever-changing environment, but its efficiency declines with age¹. Posttranscriptional regulators such as microRNAs control protein translation of target mRNAs with major consequences for development, physiology, and longevity^2,3. Here we show that food odor stimulates organismal proteostasis and promotes longevity in Caenorhabditis elegans through mir-71-mediated inhibition of tir-1 mRNA stability in olfactory AWC neurons. Screening a collection of microRNAs that control aging³ we find that miRNA mir-71 regulates lifespan and promotes ubiquitin-dependent protein turnover, particularly in the intestine. We show that mir-71 directly inhibits the toll receptor domain protein TIR-1 in AWC olfactory neurons and that disruption of mir-71/tir-1 or loss of AWC olfactory neurons eliminates the influence of food source on proteostasis. mir-71-mediated regulation of TIR-1 controls chemotactic behavior and is regulated by odor. Thus, odor perception influences cell-type specific miRNA-target interaction to regulate organismal proteostasis and longevity. We anticipate that the proposed mechanism of food perception will stimulate further research on neuroendocrine brain-to-gut communication and may open the possibility for therapeutic interventions to improve proteostasis and organismal health via the sense of smell, with potential implication for obesity, diabetes and aging.

Identification and expression profiling of microRNAs in Hymenolepis

Tapeworms (cestodes) of the genus Hymenolepis are the causative agents of hymenolepiasis, a neglected zoonotic disease. Hymenolepis nana is the most prevalent human tapeworm, especially affecting children. The genomes of Hymenolepis microstoma and H. nana have been recently sequenced and assembled. MicroRNAs (miRNAs), a class of small non-coding RNAs, are principle regulators of gene expression at the post-transcriptional level and are involved in many different biological processes. In previous work, we experimentally identified miRNA genes in the cestodes Echinococcus, Taenia and Mesocestoides. However, current knowledge about miRNAs in Hymenolepis is limited. In this work we described for the first known time the expression profile of the miRNA complement in H. microstoma, and discovered miRNAs in H. nana. We found a reduced complement of 37 evolutionarily conserved miRNAs, putatively reflecting their low morphological complexity and parasitic lifestyle. We found high expression of a few miRNAs in the larval stage of H. microstoma that are conserved in other cestodes, suggesting that these miRNAs may have important roles in development, survival and for host-parasite interplay. We performed a comparative analysis of the identified miRNAs across the Cestoda and showed that most of the miRNAs in Hymenolepis are located in intergenic regions, implying that they are independently transcribed. We found a Hymenolepis-specific cluster composed of three members of the mir-36 family. Also, we found that one of the neighboring genes of mir-10 was a Hox gene as in most bilaterial species. This study provides a valuable resource for further experimental research in cestode biology that might lead to improved detection and control of these neglected parasites. The comprehensive identification and expression analysis of Hymenolepis miRNAs can help to identify novel biomarkers for diagnosis and/or novel therapeutic targets for the control of hymenolepiasis.

Loss of miR-83 extends lifespan and affects target gene expression in an age-dependent manner in Caenorhabditis elegans

MicroRNAs (miRNAs) are short non-coding RNAs that are involved in the post-transcriptional regulation of protein-coding genes. miRNAs modulate lifespan and the aging process in a variety of organisms. In this study, we identified a role of miR-83 in regulating lifespan of Caenorhabditis elegans. mir-83 mutants exhibited extended lifespan, and the overexpression of miR-83 was sufficient to decrease the prolonged lifespan of the mutants. We observed upregulation of the expression levels of a set of miR-83 target genes in young mir-83 mutant adults; while different sets of genes were upregulated in older mir-83 mutant adults. In vivo assays showed that miR-83 regulated expression of target genes including din-1, spp-9 and col-178, and we demonstrated that daf-16 and din-1 were required for the extension of lifespan in the mir-83 mutants. The regulation of din-1 by miR-83 during aging resulted in the differential expression of din-1 targets such as gst-4 and gst-10. In daf-2 mutants, the expression level of miR-83 was significantly reduced compared to wild-type animals. We identified a role for miR-83 in modulating lifespan in C. elegans and provided molecular insights into its functional mechanism.

The Emerging Roles of microRNAs in Stem Cell Aging

Aging is the continuous loss of tissue and organ function over time. MicroRNAs (miRNAs) are thought to play a vital role in this process. miRNAs are endogenous small noncoding RNAs that control the expression of target mRNA. They are involved in many biological processes such as developmental timing, differentiation, cell death, stem cell proliferation and differentiation, immune response, aging and cancer. Accumulating studies in recent years suggest that miRNAs play crucial roles in stem cell division and differentiation. In the present chapter, we present a brief overview of these studies and discuss their contributions toward our understanding of the importance of miRNAs in normal and aged stem cell function in various model systems.

Identification and characterization of microRNAs in a cestode Hydatigera taeniaeformis using deep sequencing approach

Hydatigera taeniaeformis (formerly known as Taenia taeniaeformis) is a parasitic tapeworm that has a worldwide distribution. H. taeniaeformis is naturally transmitted between mice and cats and threatens to human health, especially those who are in close contact with pets. MicroRNAs (miRNAs) are a class of small regulatory non-coding RNAs involved in the regulation of parasite growth and development, parasite infection and immunology, and host-pathogen interactions. The miRNA profile of H. taeniaeformis remains to be elucidated. Herein, 47 conserved miRNAs (grouped into 34 miRNA families) and 4 novel miRNAs were identified in H. taeniaeformis metacestodes using deep sequencing approach. Among them, hta-miR-71, -let-7, and-miR-87 was absolutely predominant in H. taeniaeformis metacestodes. Moreover, comparative analysis revealed the presence of miR-71/2 and miR-4989/277 clusters in H. taeniaeformis. Nucleotide bias analysis of identified miRNAs showed that the adenine (A) was the dominant nucleotide at the beginning of the miRNAs, particularly at the positions of third and 7th nucleotides. The study provides rich data for further understandings of H. taeniaeformis biology.

Further Characterization of Molecular Markers in Canine Dirofilaria immitis Infection

Dirofilaria immitis is a common filarial parasite found in dogs and cats in the Americas, with the pathophysiological consequences of the infection differing somewhat between these 2 host species. Recent research efforts have been focused on determining if the microRNAs (miRNAs) released from adult Dirofilariae have a role as markers for distinguishing the intensity of adult worm infection, as well as determining the presence of new infections. This study expands previous work on 2 nematode miRNAs, miR34 and miR-71, by addressing their ability to discriminate between low and high D. immitis adult worm intensities in dogs. Serum samples were collected from 13 dogs, 8 of which carried known numbers of adult D. immitis at autopsy in their hearts and pulmonary vessels. Three groups of canine sera were created based on D. immitis burden: "control" (0 worms; 5 animals), "low intensity" (10-18 worms; mean ± SD = 12.3 ± 4.4; 4 animals), and "high intensity" (41-72 worms; mean 62.5 ± 15.1; 4 animals) groups. A qPCR analysis was performed on each sample to measure plasma levels of miR-34 and miR-71; however, no significant differences were observed between these groups in terms of levels of miRNAs, so the low- and high-intensity samples were then combined into a single "infected" category and compared to the "non-infected" controls. Copy numbers of both miR-34 and miR-71 were significantly higher in infected compared to uninfected animals ( P = 0.015 and P = 0.027, respectively). The Ct values of expression compared with the adult worm intensity for each miRNA revealed that both miR-34 and miR-71 significantly discriminate between the infected and non-infected groups ( P value < 0.0001 for both). These findings support the contention that miRNA 34 and miRNA 71, which are filarial-specific miRNAs, can both serve as biomarkers for the presence of D. immitis infection in dogs, but at this point they do not appear to reflect the actual intensity of adult parasites present.

Emerging topics in C. elegans aging research: Transcriptional regulation, stress response and epigenetics

Key discoveries in aging research have been made possible with the use of model organisms. Caenorhabditis elegans is a short-lived nematode that has become a well-established system to study aging. The practicality and powerful genetic manipulations associated with this metazoan have revolutionized our ability to understand how organisms age. 25 years after the publication of the discovery of the daf-2 gene as a genetic modifier of lifespan, C. elegans remains as relevant as ever in the quest to understand the process of aging. Nematode aging research has proven useful in identifying transcriptional regulators, small molecule signals, cellular mechanisms, epigenetic modifications associated with stress resistance and longevity, and lifespan-extending compounds. Here, we review recent discoveries and selected topics that have emerged in aging research using this incredible little worm.

Recent Molecular Genetic Explorations of Caenorhabditis elegans MicroRNAs

MicroRNAs are small, noncoding RNAs that regulate gene expression at the post-transcriptional level in essentially all aspects of Caenorhabditis elegans biology. More than 140 genes that encode microRNAs in C. elegans regulate development, behavior, metabolism, and responses to physiological and environmental changes. Genetic analysis of C. elegans microRNA genes continues to enhance our fundamental understanding of how microRNAs are integrated into broader gene regulatory networks to control diverse biological processes, including growth, cell division, cell fate determination, behavior, longevity, and stress responses. As many of these microRNA sequences and the related processing machinery are conserved over nearly a billion years of animal phylogeny, the assignment of their functions via worm genetics may inform the functions of their orthologs in other animals, including humans. In vivo investigations are especially important for microRNAs because in silico extrapolation of their functions using mRNA target prediction programs can easily assign microRNAs to incorrect genetic pathways. At this mezzanine level of microRNA bioinformatic sophistication, genetic analysis continues to be the gold standard for pathway assignments.

The miR-58 microRNA family is regulated by insulin signaling and contributes to lifespan regulation in Caenorhabditis elegans

microRNAs regulate diverse biological processes such as development and aging by promoting degradation or inhibiting translation of their target mRNAs. In this study, we have found that the miR-58 family microRNAs regulate lifespan in C. elegans. Intriguingly, members of the miR-58 family affect lifespan differently, sometimes in opposite directions, and have complex genetic interactions. The abundances of the miR-58 family miRNAs are up-regulated in the long-lived daf-2 mutant in a daf-16-dependent manner, indicating that these miRNAs are effectors of insulin signaling in C. elegans. We also found that miR-58 is regulated by insulin signaling and partially required for the lifespan extension mediated by reduced insulin signaling, germline ablation, dietary restriction, and mild mitochondrial dysfunction. We further identified the daf-21, ins-1, and isw-1 mRNAs as endogenous targets of miR-58. Our study shows that miRNAs function in multiple lifespan extension mechanisms, and that the seed sequence is not the dominant factor defining the role of a miRNA in lifespan regulation.

Neuroepigenetics of Aging and Age-Related Neurodegenerative Disorders

Neurodegenerative diseases are complex, progressive disorders and affect millions of people worldwide, contributing significantly to the global burden of disease. In recent years, research has begun to investigate epigenetic mechanisms for a potential role in disease etiology. In this chapter, we describe the current state of play for epigenetic research into neurodegenerative disorders including Alzheimer's disease, Parkinson's disease and Huntington's disease. We focus on the recent evidence for a potential role of DNA modifications, histone modifications and non-coding RNA in the etiology of these disorders. Finally, we discuss how new technological and bioinformatics advances in the field of epigenetics could further progress our understanding about the underlying mechanisms of neurodegenerative diseases.

Opposing roles of microRNA Argonautes during Caenorhabditis elegans aging

Argonaute (AGO) proteins partner with microRNAs (miRNAs) to target specific genes for post-transcriptional regulation. During larval development in Caenorhabditis elegans, Argonaute-Like Gene 1 (ALG-1) is the primary mediator of the miRNA pathway, while the related ALG-2 protein is largely dispensable. Here we show that in adult C. elegans these AGOs are differentially expressed and, surprisingly, work in opposition to each other; alg-1 promotes longevity, whereas alg-2 restricts lifespan. Transcriptional profiling of adult animals revealed that distinct miRNAs and largely non-overlapping sets of protein-coding genes are misregulated in alg-1 and alg-2 mutants. Interestingly, many of the differentially expressed genes are downstream targets of the Insulin/ IGF-1 Signaling (IIS) pathway, which controls lifespan by regulating the activity of the DAF-16/ FOXO transcription factor. Consistent with this observation, we show that daf-16 is required for the extended lifespan of alg-2 mutants. Furthermore, the long lifespan of daf-2 insulin receptor mutants, which depends on daf-16, is strongly reduced in animals lacking alg-1 activity. This work establishes an important role for AGO-mediated gene regulation in aging C. elegans and illustrates that the activity of homologous genes can switch from complementary to antagonistic, depending on the life stage.

Metazoan MicroRNAs

MicroRNAs (miRNAs) are ∼22 nt RNAs that direct posttranscriptional repression of mRNA targets in diverse eukaryotic lineages. In humans and other mammals, these small RNAs help sculpt the expression of most mRNAs. This article reviews advances in our understanding of the defining features of metazoan miRNAs and their biogenesis, genomics, and evolution. It then reviews how metazoan miRNAs are regulated, how they recognize and cause repression of their targets, and the biological functions of this repression, with a compilation of knockout phenotypes that shows that important biological functions have been identified for most of the broadly conserved miRNAs of mammals.

A microRNA feedback loop regulates global microRNA abundance during aging

Expression levels of many microRNAs (miRNAs) change during aging, notably declining globally in a number of organisms and tissues across taxa. However, little is known about the mechanisms or the biological relevance for this change. We investigated the network of genes that controls miRNA transcription and processing during C. elegans aging. We found that miRNA biogenesis genes are highly networked with transcription factors and aging-associated miRNAs. In particular, miR-71, known to influence life span and itself up-regulated during aging, represses alg-1/Argonaute expression post-transcriptionally during aging. Increased ALG-1 abundance in mir-71 loss-of-function mutants led to globally increased miRNA expression. Interestingly, these mutants demonstrated widespread mRNA expression dysregulation and diminished levels of variability both in gene expression and in overall life span. Thus, the progressive molecular decline often thought to be the result of accumulated damage over an organism's life may be partially explained by a miRNA-directed mechanism of age-associated decline.

FOXO1/3: Potential suppressors of fibrosis

Fibrosis is a universally age-related disease that involves nearly all organs. It is typically initiated by organic injury and eventually results in organ failure. There are still few effective therapeutic strategy targets for fibrogenesis. Forkhead box proteins O1 and O3 (FOXO1/3) have been shown to have favorable inhibitory effects on fibroblast activation and subsequent extracellular matrix production and can ameliorate fibrosis levels in numerous organs, including the heart, liver, lung, and kidney; they are therefore promising targets for anti-fibrosis therapy. Moreover, we can develop appropriate strategies to make the best use of FOXO1/3's anti-fibrosis properties. The information reviewed here should be significant for understanding the roles of FOXO1/3 in fibrosis and should contribute to the design of further studies related to FOXO1/3 and the fibrotic response and shed light on a potential treatment for fibrosis.

MicroRNAs mir-184 and let-7 alter Drosophila metabolism and longevity

MicroRNAs (miRNAs) are small RNA molecules that regulate gene expression associated with many complex biological processes. By comparing miRNA expression between long‐lived cohorts of Drosophila melanogaster that were fed a low‐nutrient diet with normal‐lived control animals fed a high‐nutrient diet, we identified miR‐184, let‐7, miR‐125, and miR‐100 as candidate miRNAs involved in modulating aging. We found that ubiquitous, adult‐specific overexpression of these individual miRNAs led to significant changes in fat metabolism and/or lifespan. Most impressively, adult‐specific overexpression of let‐7 in female nervous tissue increased median fly lifespan by ~22%. We provide evidence that this lifespan extension is not due to alterations in nutrient intake or to decreased insulin signaling.

An intestinal microRNA modulates the homeostatic adaptation to chronic oxidative stress in C. elegans

Adaptation to an environmental or metabolic perturbation is a feature of the evolutionary process. Recent insights into microRNA function suggest that microRNAs serve as key players in a robust adaptive response against stress in animals through their capacity to fine-tune gene expression. However, it remains largely unclear how a microRNA-modulated downstream mechanism contributes to the process of homeostatic adaptation. Here we show that loss of an intestinally expressed microRNA gene, mir-60, in the nematode C. elegans promotes an adaptive response to chronic - a mild and long-term - oxidative stress exposure. The pathway involved appears to be unique since the canonical stress-responsive factors, such as DAF-16/FOXO, are dispensable for mir-60 loss to enhance oxidative stress resistance. Gene expression profiles revealed that genes encoding lysosomal proteases and those involved in xenobiotic metabolism and pathogen defense responses are up-regulated by the loss of mir-60. Detailed genetic studies and computational microRNA target prediction suggest that endocytosis components and a bZip transcription factor gene zip-10, which functions in innate immune response, are directly modulated by miR-60 in the intestine. Our findings suggest that the mir-60 loss facilitates adaptive response against chronic oxidative stress by ensuring the maintenance of cellular homeostasis.

Differential Expression of miRNAs in the Respiratory Tree of the Sea Cucumber Apostichopus japonicus Under Hypoxia Stress

The sea cucumber, an important economic species, has encountered high mortality since 2013 in northern China because of seasonal environmental stress such as hypoxia, high temperature, and low salinity. MicroRNAs (miRNAs) are important in regulating gene expression in marine organisms in response to environmental change. In this study, high-throughput sequencing was used to investigate alterations in miRNA expression in the sea cucumber under different levels of dissolved oxygen (DO). Nine small RNA libraries were constructed from the sea cucumber respiratory trees. A total of 26 differentially expressed miRNAs, including 12 upregulated and 14 downregulated miRNAs, were observed in severe hypoxia (DO 2 mg/L) compared with mild hypoxia (DO 4 mg/L) and normoxic conditions (DO 8 mg/L). Twelve differentially expressed miRNAs were clustered in severe hypoxia. In addition, real-time PCR revealed that 14 randomly selected differentially expressed miRNAs showed significantly increased expressions in severe hypoxia and the expressions of nine miRNAs, including key miRNAs such as Aja-miR-1, Aja-miR-2008, and Aja-miR-184, were consistent with the sequencing results. Moreover, gene ontology and pathway analyses of putative target genes suggest that these miRNAs are important in redox, transport, transcription, and hydrolysis under hypoxia stress. Notably, novel-miR-1, novel-miR-2, and novel-miR-3 were specifically clustered and upregulated in severe hypoxia, which may provide new insights into novel “hypoxamiR” identification. These results will provide a basis for future studies of miRNA regulation and molecular adaptive mechanisms in sea cucumbers under hypoxia stress.

Tag team: Roles of miRNAs and Proteolytic Regulators in Ensuring Robust Gene Expression Dynamics

Lack of prominent developmental defects arising from loss of many individual miRNAs is consistent with the observations of collaborative networks between miRNAs and roles for miRNAs in regulating stress responses. However, these characteristics may only partially explain the seemingly nonessential nature of many miRNAs. Non-miRNA gene expression regulatory mechanisms also collaborate with miRNA-induced silencing complex (miRISC) to support robust gene expression dynamics. Genetic enhancer screens have revealed roles of miRNAs and other gene repressive mechanisms in development or other cellular processes that were masked by genetic redundancy. Besides discussing the breadth of the non-miRNA genes, we use LIN-28 as an example to illustrate how distinct regulatory systems, including miRNAs and multiple protein stability mechanisms, work at different levels to target expression of a given gene and provide tissue-specific and stage-specific regulation of gene expression.

Suppression of nemo-like kinase by miR-71 in Echinococcus multilocularis

Echinococcus multilocularis metacestodes are a causative pathogen for alveolar echinococcosis in human beings, and have been found to express miRNAs including emu-miR-71. miR-71 is evolutionarily conserved and highly expressed across platyhelminths, but little is known about its role. Here it was shown that emu-miR-71 was differentially expressed in protoscoleces and was unlikely to be expressed in neoblasts. The results of the luciferase assay indicated that emu-miR-71 was able to bind in vitro to the 3'-UTR of emu-nlk, encoding a key regulator of cell division, causing significant downregulation of luciferase activity (p < 0.01) compared to the negative control and the construct with mutations in the binding site. Consistent with the decreased luciferase activity, transfection of emu-miR-71 mimics into protoscoleces notably repressed emu-NLK (p < 0.05). These results demonstrate the suppression of emu-nlk by emu-miR-71, potentially involved in the protoscolex development.

Small RNAs and extracellular vesicles in filarial nematodes: From nematode development to diagnostics

Parasitic nematodes have evolved sophisticated mechanisms to communicate with their hosts in order to survive and successfully establish an infection. The transfer of RNA within extracellular vesicles (EVs) has recently been described as a mechanism that could contribute to this communication in filarial nematodes. It has been shown that these EVs are loaded with several types of RNAs, including microRNAs, leading to the hypothesis that parasites could actively use these molecules to manipulate host gene expression and to the exciting prospect that these pathways could result in new diagnostic and therapeutic strategies. Here, we review the literature on the diverse RNAi pathways that operate in nematodes and more specifically our current knowledge of extracellular RNA (exRNA) and EVs derived from filarial nematodes in vitro and within their hosts. We further detail some of the issues and questions related to the capacity of RNA-mediated communication to function in parasite-host interactions and the ability of exRNA to enable us to distinguish and detect different nematode parasites in their hosts.

Regulation of Lysosomal Function by the DAF-16 Forkhead Transcription Factor Couples Reproduction to Aging in Caenorhabditis elegans

Aging in eukaryotes is accompanied by widespread deterioration of the somatic tissue. Yet, abolishing germ cells delays the age-dependent somatic decline in Caenorhabditis elegans In adult worms lacking germ cells, the activation of the DAF-9/DAF-12 steroid signaling pathway in the gonad recruits DAF-16 activity in the intestine to promote longevity-associated phenotypes. However, the impact of this pathway on the fitness of normally reproducing animals is less clear. Here, we explore the link between progeny production and somatic aging and identify the loss of lysosomal acidity-a critical regulator of the proteolytic output of these organelles-as a novel biomarker of aging in C. elegans The increase in lysosomal pH in older worms is not a passive consequence of aging, but instead is timed with the cessation of reproduction, and correlates with the reduction in proteostasis in early adult life. Our results further implicate the steroid signaling pathway and DAF-16 in dynamically regulating lysosomal pH in the intestine of wild-type worms in response to the reproductive cycle. In the intestine of reproducing worms, DAF-16 promotes acidic lysosomes by upregulating the expression of v-ATPase genes. These findings support a model in which protein clearance in the soma is linked to reproduction in the gonad via the active regulation of lysosomal acidification.

DAF-16/FOXO Transcription Factor in Aging and Longevity

Aging is associated with age-related diseases and an increase susceptibility of cancer. Dissecting the molecular mechanisms that underlie aging and longevity would contribute to implications for preventing and treating the age-dependent diseases or cancers. Multiple signaling pathways such as the insulin/IGF-1 signaling pathway, TOR signaling, AMPK pathway, JNK pathway and germline signaling have been found to be involved in aging and longevity. And DAF-16/FOXO, as a key transcription factor, could integrate different signals from these pathways to modulate aging, and longevity via shuttling from cytoplasm to nucleus. Hence, understanding how DAF-16/FOXO functions will be pivotal to illustrate the processes of aging and longevity. Here, we summarized how DAF-16/FOXO receives signals from these pathways to affect aging and longevity. We also briefly discussed the transcriptional regulation and posttranslational modifications of DAF-16/FOXO, its co-factors as well as its potential downstream targets participating in lifespan according to the published data in C. elegans and in mammals, and in most cases, we may focus on the studies in C. elegans which has been considered to be a very good animal model for longevity research.

Aging as an Epigenetic Phenomenon

INTRODUCTION

Hypermethylation of genes associated with promoter CpG islands, and hypomethylation of CpG poor genes, repeat sequences, transposable elements and intergenic genome sections occur during aging in mammals. Methylation levels of certain CpG sites display strict correlation to age and could be used as "epigenetic clock" to predict biological age. Multi-substrate deacetylases SIRT1 and SIRT6 affect aging via locus-specific modulations of chromatin structure and activity of multiple regulatory proteins involved in aging. Random errors in DNA methylation and other epigenetic marks during aging increase the transcriptional noise, and thus lead to enhanced phenotypic variation between cells of the same tissue. Such variation could cause progressive organ dysfunction observed in aged individuals. Multiple experimental data show that induction of NF-κB regulated gene sets occurs in various tissues of aged mammals. Upregulation of multiple miRNAs occurs at mid age leading to downregulation of enzymes and regulatory proteins involved in basic cellular functions, such as DNA repair, oxidative phosphorylation, intermediate metabolism, and others.

CONCLUSION

Strong evidence shows that all epigenetic systems contribute to the lifespan control in various organisms. Similar to other cell systems, epigenome is prone to gradual degradation due to the genome damage, stressful agents, and other aging factors. But unlike mutations and other kinds of the genome damage, age-related epigenetic changes could be fully or partially reversed to a "young" state.

Micromanagement of Immune System: Role of miRNAs in Helminthic Infections

Helminthic infections fall under neglected tropical diseases, although they inflict severe morbidity to human and causes major economic burden on health care system in many developing countries. There is increased effort to understand their immunopathology in recent days due to their immuno-modulatory capabilities. Immune response is primarily controlled at the transcriptional level, however, microRNA-mediated RNA interference is emerging as important regulatory machinery that works at the translation level. In the past decade, microRNA (miRNA/miR) research has advanced with significant momentum. The result is ever increasing list of curated sequences from a broad panel of organisms including helminths. Several miRNAs had been discovered from trematodes, nematodes and cestodes like let-7, miR155, miR-199, miR-134, miR-223, miR-146, and fhe-mir-125a etc., with potential role in immune modulation. These miRs had been associated with TGF-β, MAPK, Toll-like receptor, PI3K/AKT signaling pathways and insulin growth factor regulation. Thus, controlling the immune cells development, survival, proliferation and death. Apart from micromanagement of immune system, they also express certain unique miRNA also like cis-miR-001, cis-miR-2, cis-miR-6, cis-miR-10, cis-miR-18, cis-miR-19, trs-mir-0001, fhe-miR-01, fhe-miR-07, fhe-miR-08, egr-miR-4988, egr-miR-4989 etc. The specific role played by most of these species specific unique miRs are yet to be discovered. However, these newly discovered miRNAs might serve as novel targets for therapeutic intervention or biomarkers for parasitic infections.

Genome-wide identification of microRNA targets in the neglected disease pathogens of the genus Echinococcus

MicroRNAs (miRNAs), a class of small non-coding RNAs, are key regulators of gene expression at post-transcriptional level and play essential roles in biological processes such as development. MiRNAs silence target mRNAs by binding to complementary sequences in the 3'untranslated regions (3'UTRs). The parasitic helminths of the genus Echinococcus are the causative agents of echinococcosis, a zoonotic neglected disease. In previous work, we performed a comprehensive identification and characterization of Echinococcus miRNAs. However, current knowledge about their targets is limited. Since target prediction algorithms rely on complementarity between 3'UTRs and miRNA sequences, a major limitation is the lack of accurate sequence information of 3'UTR for most species including parasitic helminths. We performed RNA-seq and developed a pipeline that integrates the transcriptomic data with available genomic data of this parasite in order to identify 3'UTRs of Echinococcus canadensis. The high confidence set of 3'UTRs obtained allowed the prediction of miRNA targets in Echinococcus through a bioinformatic approach. We performed for the first time a comparative analysis of miRNA targets in Echinococcus and Taenia. We found that many evolutionarily conserved target sites in Echinococcus and Taenia may be functional and under selective pressure. Signaling pathways such as MAPK and Wnt were among the most represented pathways indicating miRNA roles in parasite growth and development. Genome-wide identification and characterization of miRNA target genes in Echinococcus provide valuable information to guide experimental studies in order to understand miRNA functions in the parasites biology. miRNAs involved in essential functions, especially those being absent in the host or showing sequence divergence with respect to host orthologs, might be considered as novel therapeutic targets for echinococcosis control.

High-throughput identification of miRNAs of Taenia ovis, a cestode threatening sheep industry

Taenia ovis is a tapeworm that is mainly transmitted between dogs and sheep or goats and has an adverse effect on sheep industry. miRNAs are short regulatory non-coding RNAs, involved in parasite development and growth as well as parasite infection. The miRNA profile of T. ovis remains to be established. Herein, 33 known miRNAs belonging to 23 different families were identified in T. ovis metacestodes using deep sequencing approach. Of them, expression of some miRNAs such as tov-miR-10 and -let-7 was absolutely predominant. Moreover, comparative analysis revealed the presence of a miR-71/2b/2c cluster in T. ovis, which was also completely conserved in other 6 cestodes. The study provides rich data for further understandings of T. ovis biology.

MicroRNAs miR-203-3p, miR-664-3p and miR-708-5p are associated with median strain lifespan in mice

MicroRNAs (miRNAs) are small non-coding RNA species that have been shown to have roles in multiple processes that occur in higher eukaryotes. They act by binding to specific sequences in the 3’ untranslated region of their target genes and causing the transcripts to be degraded by the RNA-induced silencing complex (RISC). MicroRNAs have previously been reported to demonstrate altered expression in several aging phenotypes such as cellular senescence and age itself. Here, we have measured the expression levels of 521 small regulatory microRNAs (miRNAs) in spleen tissue from young and old animals of 6 mouse strains with different median strain lifespans by quantitative real-time PCR. Expression levels of 3 microRNAs were robustly associated with strain lifespan, after correction for multiple statistical testing (miR-203-3p [β-coefficient = −0.6447, p = 4.8 × 10⁻¹¹], miR-664-3p [β-coefficient = 0.5552, p = 5.1 × 10⁻⁸] and miR-708-5p [β-coefficient = 0.4986, p = 1.6 × 10⁻⁶]). Pathway analysis of binding sites for these three microRNAs revealed enrichment of target genes involved in key aging and longevity pathways including mTOR, FOXO and MAPK, most of which also demonstrated associations with longevity. Our results suggests that miR-203-3p, miR-664-3p and miR-708-5p may be implicated in pathways determining lifespan in mammals.

Plant-parasitic nematodes: towards understanding molecular players in stress responses

BACKGROUND

Plant-parasitic nematode interactions occur within a vast molecular plant immunity network. Following initial contact with the host plant roots, plant-parasitic nematodes (PPNs) activate basal immune responses. Defence priming involves the release in the apoplast of toxic molecules derived from reactive species or secondary metabolism. In turn, PPNs must overcome the poisonous and stressful environment at the plant-nematode interface. The ability of PPNs to escape this first line of plant immunity is crucial and will determine its virulence.

SCOPE

Nematodes trigger crucial regulatory cytoprotective mechanisms, including antioxidant and detoxification pathways. Knowledge of the upstream regulatory components that contribute to both of these pathways in PPNs remains elusive. In this review, we discuss how PPNs probably orchestrate cytoprotection to resist plant immune responses, postulating that it may be derived from ancient molecular mechanisms. The review focuses on two transcription factors, DAF-16 and SKN-1 , which are conserved in the animal kingdom and are central regulators of cell homeostasis and immune function. Both regulate the unfolding protein response and the antioxidant and detoxification pathways. DAF-16 and SKN-1 target a broad spectrum of Caenorhabditis elegans genes coding for numerous protein families present in the secretome of PPNs. Moreover, some regulatory elements of DAF-16 and SKN-1 from C. elegans have already been identified as important genes for PPN infection.

CONCLUSION

DAF-16 and SKN-1 genes may play a pivotal role in PPNs during parasitism. In the context of their hub status and mode of regulation, we suggest alternative strategies for control of PPNs through RNAi approaches.

Starvation-Induced Stress Response Is Critically Impacted by Ceramide Levels in Caenorhabditis elegans

Our understanding of the cellular mechanisms by which animals regulate their response to starvation is limited, despite the strong relevance of the problem to major human health issues. The L1 diapause of Caenorhabditis elegans, where first-stage larvae arrest in response to a food-less environment, is an excellent system to study this mechanism. We found, through genetic manipulation and lipid analysis, that biosynthesis of ceramide, particularly those with longer fatty acid side chains, critically impacts animal survival during L1 diapause. Genetic interaction analysis suggests that ceramide may act in both insulin-IGF-1 signaling (IIS)-dependent and IIS-independent pathways to affect starvation survival. Genetic and expression analyses indicate that ceramide is required for maintaining the proper expression of previously characterized starvation-responsive genes, genes that are regulated by the IIS pathway and tumor suppressor Rb, and genes responsive to pathogen. These findings provide an important insight into the roles of sphingolipid metabolism, not only in starvation response, but also in aging and food-response-related human health problems.

Stage-Wise Identification and Analysis of miRNA from Root-Knot Nematode Meloidogyne incognita

In this study, we investigated global changes in miRNAs of Meloidogyne incognita throughout its life cycle. Small RNA sequencing resulted in approximately 62, 38, 38, 35, and 39 Mb reads in the egg, J2, J3, J4, and female stages, respectively. Overall, we identified 2724 known and 383 novel miRNAs (read count > 10) from all stages, of which 169 known and 13 novel miRNA were common to all the five stages. Among the stage-specific miRNAs, miR-286 was highly expressed in eggs, miR-2401 in J2, miR-8 and miR-187 in J3, miR-6736 in J4, and miR-17 in the female stages. These miRNAs are reported to be involved in embryo and neural development, muscular function, and control of apoptosis. Cluster analysis indicated the presence of 91 miRNA clusters, of which 36 clusters were novel and identified in this study. Comparison of miRNA families with other nematodes showed 17 families to be commonly absent in animal parasitic nematodes and M. incognita. Validation of 43 predicted common and stage-specific miRNA by quantitative PCR (qPCR) indicated their expression in the nematode. Stage-wise exploration of M. incognita miRNAs has not been carried out before and this work presents information on common and stage-specific miRNAs of the root-knot nematode.

DNA damage responses and stress resistance: Concepts from bacterial SOS to metazoan immunity

The critical need for species preservation has driven the evolution of mechanisms that integrate stress signals from both exogenous and endogenous sources. Past research has been largely focused on cell-autonomous stress responses; however, recently their systemic outcomes within an organism and their implications at the ecological and species levels have emerged. Maintenance of species depends on the high fidelity transmission of the genome over infinite generations; thus, many pathways exist to monitor and restore the integrity of the genome and to coordinate DNA repair with other cellular processes, such as cell division and growth. The specifics of these DNA damage responses (DDRs) vary vastly but some general themes are conserved from ancient organisms, such as bacteria and archaea, to humans. Despite decades of research, however, DDRs still have many layers of complexity and some surprises left to be discovered. One of the most interesting current research topics is the link between DNA damage and stress resistance: the outcomes of DDRs can protect the organism from other secondary challenges. At this time, these types of responses are best characterized in bacteria and the simple metazoan model, Caenorhabditis elegans, but it is becoming clear that similar processes also exist in higher organisms.

Caenorhabditis elegans: An important tool for dissecting microRNA functions

Caenorhabditis elegans (C. elegans), a member of the phylum Nematoda, carries the evolutionarily conserved genes comparing to mammals. Due to its short lifespan and completely sequenced genome, C. elegans becomes a potentially powerful model for mechanistic studies in human diseases. In this mini review, we will outline the current understandings on C. elegans as a model organism for microRNA (miRNA)-related research in the pathogenesis of human diseases.

Roles for ROS and hydrogen sulfide in the longevity response to germline loss in Caenorhabditis elegans

In Caenorhabditis elegans, removing germ cells slows aging and extends life. Here we show that transcription factors that extend life and confer protection to age-related protein-aggregation toxicity are activated early in adulthood in response to a burst of reactive oxygen species (ROS) and a shift in sulfur metabolism. Germline loss triggers H2S production, mitochondrial biogenesis, and a dynamic pattern of ROS in specific somatic tissues. A cytoskeletal protein, KRI-1, plays a key role in the generation of H2S and ROS. These kri-1-dependent redox species, in turn, promote life extension by activating SKN-1/Nrf2 and the mitochondrial unfolded-protein response, respectively. Both H2S and, remarkably, kri-1-dependent ROS are required for the life extension produced by low levels of the superoxide-generator paraquat and by a mutation that inhibits respiration. Together our findings link reproductive signaling to mitochondria and define an inducible, kri-1-dependent redox-signaling module that can be invoked in different contexts to extend life and counteract proteotoxicity.