Project description:Investigated the specific miRNAs that are assocaited with ALG-1 and ALG-2 in adult (D5) C. elegans. ALG-1 and ALG-2 were IP-ed from D5 collected C.elegans, RNA was isolated and used for small RNA sequencing. Two biological replicates were used.
Project description:Caenorhabditis elegans contains twenty-five Argonautes, of which, only ALG-1 and ALG-2 are known to interact with miRNAs. ALG-5 belongs to the AGO subfamily of Argonautes that includes ALG-1 and ALG-2, but its role in small RNA pathways is unknown. We analyzed by high-throughput sequencing the small RNAs associated with ALG-5, ALG-1, and ALG-2, as well as changes in mRNA expression in alg-5, alg-1, and alg-2 mutants.
Project description:MicroRNAs (miRNA) associate with Argonaute proteins and negatively regulate gene expression by base pairing with complementary sequences in the 3’ UTRs of target genes. De novo coding variants in the human Argonaute gene AGO1 were reported to cause neurodevelopmental disorder (NDD) with intellectual disability (ID). Most of the altered amino acids are conserved between the miRNA associated Argonautes in H. sapiens and C. elegans, suggesting that the human AGO1 mutations could disrupt evolutionarily conserved functions in miRNA biogenesis or target repression. We genetically modeled four human AGO1 mutations in C. elegans by introducing identical mutations into the C. elegans AGO1 homolog, ALG-1. These alg-1 NDD mutations caused phenotypes in C. elegans indicative of disrupted miRNA processing, miRISC formation, and/or target repression. We show that the alg-1 NDD mutations are antimorphic as they cause developmental and molecular phenotypes stronger than those exhibited by the alg-1 null mutants, likely by sequestrating functional miRNA silencing complex (miRISC) components into non-functional complexes that fail to confer robust gene repression. The alg-1 NDD mutations cause allele-specific disruptions in mature miRNA profiles, both in overall abundances and ALG-1 NDD association, accompanied by perturbation of downstream gene expression, including altered translational efficiency and/or mRNA abundance. The perturbed genes include those with human orthologs whose dysfunction is associated with NDD. These cross-clade genetic studies illuminate fundamental Argonaute functions and provide insights into the conservation of miRNA-mediated post-transcriptional regulatory mechanisms.
Project description:microRNAs fine-tune the regulation of numerous biological processes by mediating gene expression post-transcriptionally. Mature miRNAs associate with argonaute (AGO) proteins to form the RNA-induced silencing complex (RISC) that binds to and blocks translation of target mRNAs. In our study, we address the function of miRNAs in regulating DNA damage responses in-vivo, by exploiting the nematode model organism Caenorhabditis elegans. Using next-generation sequencing, we obtained miRNA expression profiles of WT worms as well as mutants harboring a loss-of-function deletion of the C. elegans AGO gene alg-2 that display abnormal cell death in response to genotoxic stress. 2.5 hours after exposure to ionizing irradiation, the miRNA transcriptomes of both WT and alg-2(ok304) mutant worms were only mildly altered in comparison to their respective untreated controls. However, irrespective of treatment, alg-2(ok304) mutants exhibited noticeable dysregulation of several miRNA families with known physiological functions. Reduced levels of some of these miRNAs might explain the abnormal DNA damage response of alg-2-deficient C. elegans.
Project description:We aimed to characterize the cell-type specific loading patterns of miRNAs in c.elegans. We expressed cell-type specific HA-epitope tagged versions of Argonaute-like 1 (ALG-1) and ALG-2 from three major tissue types i.e. intestine, nervous system and body wall mucle. We found that most miRNAs display highly cell-type specific loading patterns. ALG-1 is more ubiquitously loaded whereas ALG-2 is eniriched for miRNA loading within the nervous system. Addtionally we show that there is flexibility in ALG loading which changes during the aging process.
Project description:MicroRNAs (miRNA) associate with Argonaute proteins and negatively regulate gene expression by base pairing with complementary sequences in the 3’ UTRs of target genes. De novo coding variants in the human Argonaute gene AGO1 were reported to cause neurodevelopmental disorder (NDD) with intellectual disability (ID). Most of the altered amino acids are conserved between the miRNA associated Argonautes in H. sapiens and C. elegans, suggesting that the human AGO1 mutations could disrupt evolutionarily conserved functions in miRNA biogenesis or target repression. We genetically modeled four human AGO1 mutations in C. elegans by introducing identical mutations into the C. elegans AGO1 homolog, ALG-1. These alg-1 NDD mutations caused phenotypes in C. elegans indicative of disrupted miRNA processing, miRISC formation, and/or target repression. We show that the alg-1 NDD mutations are antimorphic as they cause developmental and molecular phenotypes stronger than those exhibited by the alg-1 null mutants, likely by sequestrating functional miRNA silencing complex (miRISC) components into non-functional complexes that fail to confer robust gene repression. The alg-1 NDD mutations cause allele-specific disruptions in mature miRNA profiles, both in overall abundances and ALG-1 NDD association, accompanied by perturbation of downstream gene expression, including altered translational efficiency and/or mRNA abundance. The perturbed genes include those with human orthologs whose dysfunction is associated with NDD. These cross-clade genetic studies illuminate fundamental Argonaute functions and provide insights into the conservation of miRNA-mediated post-transcriptional regulatory mechanisms.
Project description:MicroRNAs (miRNA) associate with Argonaute proteins and negatively regulate gene expression by base pairing with complementary sequences in the 3’ UTRs of target genes. De novo coding variants in the human Argonaute gene AGO1 were reported to cause neurodevelopmental disorder (NDD) with intellectual disability (ID). Most of the altered amino acids are conserved between the miRNA associated Argonautes in H. sapiens and C. elegans, suggesting that the human AGO1 mutations could disrupt evolutionarily conserved functions in miRNA biogenesis or target repression. We genetically modeled four human AGO1 mutations in C. elegans by introducing identical mutations into the C. elegans AGO1 homolog, ALG-1. These alg-1 NDD mutations caused phenotypes in C. elegans indicative of disrupted miRNA processing, miRISC formation, and/or target repression. We show that the alg-1 NDD mutations are antimorphic as they cause developmental and molecular phenotypes stronger than those exhibited by the alg-1 null mutants, likely by sequestrating functional miRNA silencing complex (miRISC) components into non-functional complexes that fail to confer robust gene repression. The alg-1 NDD mutations cause allele-specific disruptions in mature miRNA profiles, both in overall abundances and ALG-1 NDD association, accompanied by perturbation of downstream gene expression, including altered translational efficiency and/or mRNA abundance. The perturbed genes include those with human orthologs whose dysfunction is associated with NDD. These cross-clade genetic studies illuminate fundamental Argonaute functions and provide insights into the conservation of miRNA-mediated post-transcriptional regulatory mechanisms.
Project description:Argonaute proteins are at the core of the microRNA-mediated gene silencing pathway essential for animals. In C. elegans, the microRNA-specific Argonautes ALG-1 and ALG-2 regulate multiple processes required for proper animal developmental timing and viability. Here, we identified a new phosphorylation site, serine 642, on ALG-1 that modulates microRNA association. Mutating ALG-1 serine 642 into a phospho-mimicking residue impairs microRNA binding and causes embryonic lethality and post-embryonic phenotypes that are common with alteration of microRNA functions. Monitoring microRNA levels in alg-1 phosphorylation mutant animals reveal that miRNA passenger strands strongly increase but are not preferentially loaded into ALG-1, indicating that the miRNA binding defects could also lead to miRNA duplexes accumulation. Our genetic and biochemical experiments support the protein kinase A KIN-1 as the putative kinase that phosphorylates ALG-1 serine 642. Altogether, our data indicate that PKA triggers the ALG-1 phosphorylation to regulate its microRNAs association during C. elegans development.
Project description:Here, we report a new phosphorylation site on ALG-1 that modulates its ability to bind miRNAs. Mutating ALG-1 S642 into a phosphomimetic residue strongly impairs binding to miRNAs. Furthermore, this mutation causes embryonic lethality which are not observed in animals depleted of alg-1 suggesting that it may consequently impair the normal function of its homolog alg-2. Quantification of miRNAs in the phosphorylation mutants of alg-1 reveals that the miRNA passenger strands are strongly increased but not preferentially loaded into ALG-1, indicating that the defects in miRNA binding may also lead to an accumulation of miRNA duplexes.