Project description:We report the identification of small RNAs in undifferentiated (d0) and differentiating (d4) mouse embryonic stem (ES) cells using high-throughput sequencing. The goal of this study was to identify small RNAs involved in X-chromosome inactivation (XCI). We have identified a subset of small RNAs that are generated from transposon sequences and map to the X-chromosome, suggesting their involvement in transposon control on the inactivating X-chromosome.
Project description:RNA-interference (RNAi) refers to a growing class of gene silencing phenomena defined by a requirement for small RNAs of 20-32 nt and the action of the Argonaute (Ago) family of ribonucleases. We have previously identified developmentally regulated small RNAs, using Northern blot analysis, that are expressed during X-chromosome inactivation in differentiating female mouse ES cels. We sought to identify these small RNAs using deep sequencing. We identified small RNAs that align to retrotransposon sequences and are enriched on the X-chromosome. LINE elements have been proposed to act as way stations during X-inactivation for the spreading of silencing along the entire chromosome, and our findings suggest that LINE elements found on the X-chromosome may be enriched for small RNAs relative to the genome. These results suggest that RNAi pathways are involved in regulating LINE elements during X-inactivation and ES cell differentiation. We size-fractionated total RNA from differentiating female mouse ES cells (day 4) into 18-24 nt and 25-45 nt populations and sequenced each fraction separately using the 454 platform. We used a karyotypically stable 40XX female ES cell line (EL16.7) with one X each of 129 and M. castaneus origins: 129 x (M.castaneus x 129).
Project description:Small RNAs are emerging as important molecules for cross-species communication. Thanks to available and affordable sequencing technologies it is now possible to sequence small RNAs (sRNA-Seq) present in samples of interacting organisms. A first step when analyzing sRNA-Seq of two interacting species is to determine which sequences are being produced by which organism. Due to their small size (18-30), small RNAs could easily map to both host and parasite genomes. Here we produced data for Mus musculus intestinal epithelial cells treated with Extracellular Vesicles (EV) produced by the parasitic nematode Heligmosomoides bakeri.
Project description:Introgressed variants from other species can be an important source of genetic variation because they may arise rapidly, can include multiple mutations on a single haplotype, and have often been pretested by selection in the species of origin. Although introgressed alleles are generally deleterious, several studies have reported introgression as the source of adaptive alleles-including the rodenticide-resistant variant of Vkorc1 that introgressed from Mus spretus into European populations of Mus musculus domesticus. Here, we conducted bidirectional genome scans to characterize introgressed regions into one wild population of M. spretus from Spain and three wild populations of M. m. domesticus from France, Germany, and Iran. Despite the fact that these species show considerable intrinsic postzygotic reproductive isolation, introgression was observed in all individuals, including in the M. musculus reference genome (GRCm38). Mus spretus individuals had a greater proportion of introgression compared with M. m. domesticus, and within M. m. domesticus, the proportion of introgression decreased with geographic distance from the area of sympatry. Introgression was observed on all autosomes for both species, but not on the X-chromosome in M. m. domesticus, consistent with known X-linked hybrid sterility and inviability genes that have been mapped to the M. spretus X-chromosome. Tract lengths were generally short with a few outliers of up to 2.7 Mb. Interestingly, the longest introgressed tracts were in olfactory receptor regions, and introgressed tracts were significantly enriched for olfactory receptor genes in both species, suggesting that introgression may be a source of functional novelty even between species with high barriers to gene flow.