Project description:RNA interference (RNAi) is widely used to determine the function of genes. We chose this approach to assess the collective function of the highly related reproductive homeobox 3 (Rhox3) gene paralogs. Using a Rhox3 short hairpin (sh) RNA with 100% complementarity to all 8 Rhox3 paralogs, expressed from a CRE-regulated transgene, we successfully knocked down Rhox3 expression in male germ cells in vivo. These Rhox3-shRNA transgenic mice had dramatic defects in spermatogenesis, primarily in spermatocytes and round spermatids. To determine whether this phenotype was caused by reduced Rhox3 expression, we generated mice expressing the Rhox3-shRNA but lacking the intended target of the shRNA – Rhox3. These double-mutant mice had a phenotype indistinguishable from Rhox3-shRNA-expressing mice that was different from mice lacking the Rhox3 paralogs, indicating that the Rhox3 shRNA disrupts spermatogenesis independently of Rhox3. Rhox3-shRNA transgenic mice displayed few alterations in the expression of protein-coding genes, but instead exhibited reduced levels of all endogenous siRNAs we tested. This supported a model in which the Rhox3 shRNA causes spermatogenic defects by sequestering one or more components of the endogenous small RNA biogenesis machinery. Our study serves as a warning for those using shRNA approaches to investigate gene functions in vivo. Comparison of total RNA from post-natal day 15 testis extracted from three wild-type mice and three transgenic mice genetically engineered to express siRNA designed to knock-down Rhox3. RNA hybridised to Affymetrix mouse all exon arrays.
Project description:RNA interference (RNAi) is widely used to determine the function of genes. We chose this approach to assess the collective function of the highly related reproductive homeobox 3 (Rhox3) gene paralogs. Using a Rhox3 short hairpin (sh) RNA with 100% complementarity to all 8 Rhox3 paralogs, expressed from a CRE-regulated transgene, we successfully knocked down Rhox3 expression in male germ cells in vivo. These Rhox3-shRNA transgenic mice had dramatic defects in spermatogenesis, primarily in spermatocytes and round spermatids. To determine whether this phenotype was caused by reduced Rhox3 expression, we generated mice expressing the Rhox3-shRNA but lacking the intended target of the shRNA – Rhox3. These double-mutant mice had a phenotype indistinguishable from Rhox3-shRNA-expressing mice that was different from mice lacking the Rhox3 paralogs, indicating that the Rhox3 shRNA disrupts spermatogenesis independently of Rhox3. Rhox3-shRNA transgenic mice displayed few alterations in the expression of protein-coding genes, but instead exhibited reduced levels of all endogenous siRNAs we tested. This supported a model in which the Rhox3 shRNA causes spermatogenic defects by sequestering one or more components of the endogenous small RNA biogenesis machinery. Our study serves as a warning for those using shRNA approaches to investigate gene functions in vivo.
Project description:Short interfering RNAs (siRNAs) are a class of regulatory effectors that enforce gene silencing though formation of RNA duplexes. While progress has been made in identifying the capabilities of siRNAs in silencing of foreign RNA and transposable elements, siRNA functions in endogenous gene regulation have remained mysterious. In certain organisms, siRNA biosynthesis involves novel enzymes that act as RNA-directed RNA polymerases (RdRPs). Here we analyze the function of a C. elegans RdRP, RRF-3, during spermatogenesis. We found that loss of RRF-3 function resulted in pleiotropic defects in sperm development, and that sperm defects led to embryonic lethality. Notably, sperm nuclei in mutants of either rrf-3 or another component of the siRNA pathway, eri-1, were frequently surrounded by ectopic microtubule structures, with spindle abnormalities in a subset of the resulting embryos. Through high-throughput small RNA sequencing, we identified a population of cellular mRNAs from spermatogenic cells that appear to serve as templates for antisense siRNA synthesis. This set of genes includes the majority of genes known to have enriched expression during spermatogenesis, as well as many genes not previously known to be expressed during spermatogenesis. For a subset of these genes, we found that RRF-3 was required for effective siRNA accumulation. These and other data suggest a working model in which a major role for the RRF-3/ERI pathway is to generate siRNAs that set patterns of gene expression through feedback repression of a set of critical targets during spermatogenesis Sequencing of small RNAs from a population of C. elegans isolated spermatogenic cells and from two paired sets of rrf-3 mutant and control whole males
Project description:We collected testes biopsies from NOA (severe spermatogenic defects, no spermatids or sperm) and OA (normal spermatogenesis, tubular lumen obstruction) patients for iTRAQ proteomics analyses, to screen the genes for which the altered expression is involved in spermatogenic defects
Project description:We analyzed miRNA-based shRNA off-target effects by transducing Trp53-/- MEFs at single- and high-copy with six well-characterized, potent and weak Trp53 shRNAs. To advance RNAi therapy for KRAS-mutant cancer, we developed a functionally validated library of siRNAs against RAS pathway genes that minimize off-target effects and enable combination gene silencing at low dose. We developed an in vivo model for real-time tracking of nanoparticle-based siRNA delivery and offer proof-of-principle that siRNA-mediated inhibition of a single gene (KRAS) or combinations of genes (A/B/C-RAF or KRAS+PIK3C-A/B) can impair the growth of KRAS-mutant colorectal cancer xenografts.
Project description:We tested the most widely used control siRNA directed against GFP for off-target effects and found by genome-wide expression profiling that it deregulates in addition to GFP a set of endogenous target genes. The detected modulated mRNA had target sequences homologous to the siRNA as small as 9 bp in size. However, we found no restriction of sequence homology to 3'UTR of target genes. Keywords: RNAi knock down
Project description:Short interfering RNAs (siRNAs) are a class of regulatory effectors that enforce gene silencing though formation of RNA duplexes. While progress has been made in identifying the capabilities of siRNAs in silencing of foreign RNA and transposable elements, siRNA functions in endogenous gene regulation have remained mysterious. In certain organisms, siRNA biosynthesis involves novel enzymes that act as RNA-directed RNA polymerases (RdRPs). Here we analyze the function of a C. elegans RdRP, RRF-3, during spermatogenesis. We found that loss of RRF-3 function resulted in pleiotropic defects in sperm development, and that sperm defects led to embryonic lethality. Notably, sperm nuclei in mutants of either rrf-3 or another component of the siRNA pathway, eri-1, were frequently surrounded by ectopic microtubule structures, with spindle abnormalities in a subset of the resulting embryos. Through high-throughput small RNA sequencing, we identified a population of cellular mRNAs from spermatogenic cells that appear to serve as templates for antisense siRNA synthesis. This set of genes includes the majority of genes known to have enriched expression during spermatogenesis, as well as many genes not previously known to be expressed during spermatogenesis. For a subset of these genes, we found that RRF-3 was required for effective siRNA accumulation. These and other data suggest a working model in which a major role for the RRF-3/ERI pathway is to generate siRNAs that set patterns of gene expression through feedback repression of a set of critical targets during spermatogenesis
Project description:RNA interference (RNAi) is an evolutionarily conserved phenomenon of post-transcriptional gene silencing mediated by small interfering RNAs (siRNAs) generated from short hairpin RNAs (shRNAs) by Dicer cleavage. Here, we report that siRNA precursors can be divided into two categories with different processing mechanisms and silencing activities that are dependent on stem loop length. We designed an alternative siRNA precursor for triggering RNAi named single-stranded Argonaute2 (Ago2)-processed interfering RNA (saiRNA). saiRNA is composed of a 16-18 bp stem and a loop complementary to the target transcript. The introduction of a self-cleavage ribozyme derived from hepatitis delta virus (HDV) to the 3’ end of the saiRNA dramatically improved its silencing activity. Unlike classical shRNA, the strand-specific cleavage of saiRNA by Ago2 during its processing not only eliminated the passenger strand but also avoided the association of mature siRNA with non-nucleolytic Ago proteins, thereby further reducing the risk of off-target effects. Additionally, saiRNA exhibited less competition with the biogenesis of endogenous miRNAs. Therefore, HDV ribozyme-enhanced saiRNA provides a reliable tool for RNAi applications.