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.
Project description:In the murine system, Oct4, Sox2, c-Myc and Klf4 are sufficient to convert fibroblasts to induced pluripotent stem (iPS) cells that exhibit many characteristics of embryonic stem (ES) cells. Herein, we show that the orphan nuclear receptor Esrrb works in conjunction with Oct4 and Sox2 to mediate reprogramming of mouse embryonic fibroblasts (MEFs) to iPS cells. Esrrb reprogrammed cells share similar expression and epigenetic signatures as ES cells. These cells are also pluripotent and can differentiate in vitro and in vivo into the three major embryonic cell lineages. Furthermore, these cells contribute to mouse chimeras and are germline transmissible. In ES cells, Esrrb targets many genes involved in selfrenewal and pluripotency. This suggests that Esrrb may mediate reprogramming through the up-regulation of ES cell-specific genes. Our findings also indicate that it is possible to reprogram MEFs without exogenous Klf transcription factors and link a nuclear receptor to somatic cell reprogramming. Global gene expression effects of silencing the Esrrb gene. We used microarrays to detail the global programme of gene expression after silencing the Esrrb gene. Keywords: time-course Three biological replicates each for control GFP and Esrrb RNAi. The global gene expression profiles of the Esrrb knockdown cells were compared to control GFP knockdown cells for days 2, 4 and 6.