Project description:Master transcription factors are the gatekeepers of lineage identity. As such, they have been a major focus of efforts to manipulate cell fate for therapeutic purposes. The ETS transcription factor PU.1 has a potent ability to confer macrophage phenotypes on cells already committed to a different lineage, but how it overcomes the presence of other master regulators is not known. The nuclear receptor PPARγ is the master regulator of the adipose lineage, and its genomic binding pattern is well characterized in adipocytes. Here, we show that when expressed at macrophage levels in mature adipocytes, PU.1 bound a large fraction of its macrophage sites, where it induced chromatin opening and the expression of macrophage target genes. Strikingly, PU.1 markedly reduced the genomic binding of PPARγ without changing its abundance. PU.1 expression repressed genes with nearby adipocyte-specific PPARγ binding sites, while a common macrophage-adipocyte gene expression program was retained. Together, these data reveal unexpected lability within the adipocyte PPARγ cistrome and show that even in terminally differentiated cells, PU.1 can remodel the cistrome of another master regulator. Microarray expression profiling was performed on 3T3-L1 adipocytes from two treatment groups: (1) adipocytes transduced with a control adenovirus expressing beta-galactosidase (LACZ-Ads) and (2) adipocytes transduced with an adenovirus expressing full-length murine PU.1 cDNA (PU.1-Ads). Each sample group consists of four biological replicates which are here defined as separate differentiations of mature 3T3-L1 adipocytes and adenoviral infections. Each replicate was hybridized to an individual array for a total of eight arrays.
Project description:Master transcription factors are the gatekeepers of lineage identity. As such, they have been a major focus of efforts to manipulate cell fate for therapeutic purposes. The ETS transcription factor PU.1 has a potent ability to confer macrophage phenotypes on cells already committed to a different lineage, but how it overcomes the presence of other master regulators is not known. The nuclear receptor PPARγ is the master regulator of the adipose lineage, and its genomic binding pattern is well characterized in adipocytes. Here, we show that when expressed at macrophage levels in mature adipocytes, PU.1 bound a large fraction of its macrophage sites, where it induced chromatin opening and the expression of macrophage target genes. Strikingly, PU.1 markedly reduced the genomic binding of PPARγ without changing its abundance. PU.1 expression repressed genes with nearby adipocyte-specific PPARγ binding sites, while a common macrophage-adipocyte gene expression program was retained. Together, these data reveal unexpected lability within the adipocyte PPARγ cistrome and show that even in terminally differentiated cells, PU.1 can remodel the cistrome of another master regulator.
Project description:"Master" transcription factors are the gatekeepers of lineage identity. As such, they have been a major focus of efforts to manipulate cell fate for therapeutic purposes. The ETS transcription factor PU.1 has a potent ability to confer macrophage phenotypes on cells already committed to a different lineage, but how it overcomes the presence of other master regulators is not known. The nuclear receptor PPARγ is the master regulator of the adipose lineage, and its genomic binding pattern is well characterized in adipocytes. Here, we show that when expressed at macrophage levels in mature adipocytes, PU.1 bound a large fraction of its macrophage sites, where it induced chromatin opening and the expression of macrophage target genes. Strikingly, PU.1 markedly reduced the genomic binding of PPARγ without changing its abundance. PU.1 expression repressed genes with nearby adipocyte-specific PPARγ binding sites, while a common macrophage-adipocyte gene expression program was retained. Together, these data reveal unexpected lability within the adipocyte PPARγ cistrome and show that even in terminally differentiated cells, PU.1 can remodel the cistrome of another master regulator.
Project description:"Master" transcription factors are the gatekeepers of lineage identity. As such, they have been a major focus of efforts to manipulate cell fate for therapeutic purposes. The ETS transcription factor PU.1 has a potent ability to confer macrophage phenotypes on cells already committed to a different lineage, but how it overcomes the presence of other master regulators is not known. The nuclear receptor PPARM-NM-3 is the master regulator of the adipose lineage, and its genomic binding pattern is well characterized in adipocytes. Here, we show that when expressed at macrophage levels in mature adipocytes, PU.1 bound a large fraction of its macrophage sites, where it induced chromatin opening and the expression of macrophage target genes. Strikingly, PU.1 markedly reduced the genomic binding of PPARM-NM-3 without changing its abundance. PU.1 expression repressed genes with nearby adipocyte-specific PPARM-NM-3 binding sites, while a common macrophage-adipocyte gene expression program was retained. Together, these data reveal unexpected lability within the adipocyte PPARM-NM-3 cistrome and show that even in terminally differentiated cells, PU.1 can remodel the cistrome of another master regulator. ChIP-seq was performed on 3T3-L1 adipocytes from two treatment groups: (1) adipocytes transduced with a control adenovirus expressing beta-galactosidase (LACZ-Ads) and (2) adipocytes transduced with an adenovirus expressing full-length murine PU.1 cDNA (PU.1-Ads). Nuclear lysates from each group were used for PPARg ChIP. For PU.1-Ads, PU.1 ChIP was also performed. To generate chromatin for ChIP-seq, DNA from three immunoprecipitations per condition was pooled. This process was repreated from a second set of L1 adipocytes to generate two biological replicates for sequencing. Genomic input DNA was sequenced from the first biological replicate only.
Project description:PU.1 is a prototype master transcription factor (TF) of hematopoietic cell differentiation with diverse roles in different lineages. Analysis of its genome-wide binding pattern across PU.1 expressing cell types revealed manifold cell type-specific binding patterns. They are not consistent with the epigenetic and chromatin constraints to PU.1 binding observed in vitro, suggesting that PU.1 requires auxiliary factors to access DNA in vivo. Using a model of transient mRNA expression we show that PU.1 induction leads to the extensive remodeling of chromatin, redistribution of partner transcription factors and rapid initiation of a myeloid gene expression program in heterologous cell types. By probing PU.1 mutants for defects in chromatin access and screening for PU.1 proximal proteins in vivo, we found that its N-terminal acidic domain was required for the recruitment of SWI/SNF remodeling complexes, de novo chromatin access and stable binding as well as the redistribution of partner TFs.
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:A transcriptome study in mouse hematopoietic stem cells was performed using a sensitive SAGE method, in an attempt to detect medium and low abundant transcripts expressed in these cells. Among a total of 31,380 unique transcript, 17,326 (55%) known genes were detected, 14,054 (45%) low-copy transcripts that have no matches to currently known genes. 3,899 (23%) were alternatively spliced transcripts of the known genes and 3,754 (22%) represent anti-sense transcripts from known genes.
Project description:Translational research is commonly performed in the C57B6/J mouse strain, chosen for its genetic homogeneity and phenotypic uniformity. Here, we evaluate the suitability of the white-footed deer mouse (Peromyscus leucopus) as a model organism for aging research, offering a comparative analysis against C57B6/J and diversity outbred (DO) Mus musculus strains. Our study includes comparisons of body composition, skeletal muscle function, and cardiovascular parameters, shedding light on potential applications and limitations of P. leucopus in aging studies. Notably, P. leucopus exhibits distinct body composition characteristics, emphasizing reduced muscle force exertion and a unique metabolism, particularly in fat mass. Cardiovascular assessments showed changes in arterial stiffness, challenging conventional assumptions and highlighting the need for a nuanced interpretation of aging-related phenotypes. Our study also highlights inherent challenges associated with maintaining and phenotyping P. leucopus cohorts. Behavioral considerations, including anxiety-induced responses during handling and phenotyping assessment, pose obstacles in acquiring meaningful data. Moreover, the unique anatomy of P. leucopus necessitates careful adaptation of protocols designed for Mus musculus. While showcasing potential benefits, further extensive analyses across broader age ranges and larger cohorts are necessary to establish the reliability of P. leucopus as a robust and translatable model for aging studies.