Project description:Hematopoietic cells arise from spatiotemporally restricted domains in the developing embryo. Although studies of non-mammalian animal and in vitro embryonic stem cell models suggest a close relationship among cardiac, endocardial, and hematopoietic lineages, it remains unknown whether the mammalian heart tube serves as a hemogenic organ akin to the dorsal aorta. Here, we examined the hemogenic activity of the developing endocardium. Mouse heart explants generated myeloid and erythroid colonies in the absence of circulation. Hemogenic activity arose from a subset of endocardial cells in the outflow cushion and atria earlier than in the aorta-gonad-mesonephros region, and was transient and definitive in nature. Interestingly, key cardiac transcription factors, Nkx2-5 and Isl1, were expressed in and required for the hemogenic activity of the endocardium. Together, these data suggest that a subset of endocardial and yolk sac endothelial cells expressing cardiac markers serve as a de novo source for transient definitive hematopoietic progenitors. Two independent biological duplicates of freshly isolated mouse tissues (caudal half, heart tube, yolk sac) were sorted for CD31+/CD41-/CD45- cells.
Project description:Hematopoietic cells arise from spatiotemporally restricted domains in the developing embryo. Although studies of non-mammalian animal and in vitro embryonic stem cell models suggest a close relationship among cardiac, endocardial, and hematopoietic lineages, it remains unknown whether the mammalian heart tube serves as a hemogenic organ akin to the dorsal aorta. Here, we examined the hemogenic activity of the developing endocardium. Mouse heart explants generated myeloid and erythroid colonies in the absence of circulation. Hemogenic activity arose from a subset of endocardial cells in the outflow cushion and atria earlier than in the aorta-gonad-mesonephros region, and was transient and definitive in nature. Interestingly, key cardiac transcription factors, Nkx2-5 and Isl1, were expressed in and required for the hemogenic activity of the endocardium. Together, these data suggest that a subset of endocardial and yolk sac endothelial cells expressing cardiac markers serve as a de novo source for transient definitive hematopoietic progenitors.
Project description:To investigate roles for Tbx20 in endocardium, we ablated Tbx20 utilizing Tie2Cre. Tie2Cre;Tbx20 mutants died at E14, exhibiting defects in multiple aspects of cardiac septation. Although endocardial cells lacking Tbx20 were able to undergo endothelial-to-mesenchymal transition, cushion mesenchymal cells lacking Tbx20 did not disperse normally. Non-cell autonomous roles of endocardial Tbx20 were also revealed, as evidenced by decreased myocardialization of outflow tract and failure of dorsal mesenchymal protrusion formation in mutants. To examine how ablation of Tbx20 in endocardial lineages affected gene expression, we performed global gene expression analysis on purified endocardial lineages. E12.5 hearts were dissociated, and Tie2Cre;RosatdTom lineage traced cells of controls and mutants were isolated by fluorescence activated cell sorting (FACS), after exclusion of blood cells (Ter119+, CD41+ and/or CD45+). Mutant endocardial lineages exhibited decreased expression of genes associated with extracellular matrix and cell migration. E12.5 hearts were dissociated, and Tie2Cre;RosatdTom lineage traced cells of controls and mutants were isolated by fluorescence activated cell sorting (FACS), after exclusion of blood cells (Ter119+, CD41+ and/or CD45+). FACS sorted Tie2Cre lineage from E12.5 hearts: Tie2Cre;Tbx20 +/loxP Control hearts versus Tie2Cre;Tbx20 loxP/- mutant hearts
Project description:To investigate roles for Tbx20 in endocardium, we ablated Tbx20 utilizing Tie2Cre. Tie2Cre;Tbx20 mutants died at E14, exhibiting defects in multiple aspects of cardiac septation. Although endocardial cells lacking Tbx20 were able to undergo endothelial-to-mesenchymal transition, cushion mesenchymal cells lacking Tbx20 did not disperse normally. Non-cell autonomous roles of endocardial Tbx20 were also revealed, as evidenced by decreased myocardialization of outflow tract and failure of dorsal mesenchymal protrusion formation in mutants. To examine how ablation of Tbx20 in endocardial lineages affected gene expression, we performed global gene expression analysis on purified endocardial lineages. E12.5 hearts were dissociated, and Tie2Cre;RosatdTom lineage traced cells of controls and mutants were isolated by fluorescence activated cell sorting (FACS), after exclusion of blood cells (Ter119+, CD41+ and/or CD45+). Mutant endocardial lineages exhibited decreased expression of genes associated with extracellular matrix and cell migration. E12.5 hearts were dissociated, and Tie2Cre;RosatdTom lineage traced cells of controls and mutants were isolated by fluorescence activated cell sorting (FACS), after exclusion of blood cells (Ter119+, CD41+ and/or CD45+).
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:The majority of congenital heart disease cases lack a definitive cause, suggesting the role of gene-environment interactions (GxE) in disease pathogenesis. Maternal diabetes mellitus (matDM) is among the most prevalent environmental risk factors for CHD and matDM associated oxidative stress is known to disrupt cardiac development. Here, we demonstrate that NOTCH1 haploinsufficient endothelial cells have an altered transcriptomic response to oxidative stress compared to control endothelial cells, with an exacerbated effect on gene regulatory networks crucial for endocardial cushion morphogenesis.
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.
Project description:BackgroundCopy number variation is an important dimension of genetic diversity and has implications in development and disease. As an important model organism, the mouse is a prime candidate for copy number variant (CNV) characterization, but this has yet to be completed for a large sample size. Here we report CNV analysis of publicly available, high-density microarray data files for 351 mouse tail samples, including 290 mice that had not been characterized for CNVs previously.ResultsWe found 9634 putative autosomal CNVs across the samples affecting 6.87% of the mouse reference genome. We find significant differences in the degree of CNV uniqueness (single sample occurrence) and the nature of CNV-gene overlap between wild-caught mice and classical laboratory strains. CNV-gene overlap was associated with lipid metabolism, pheromone response and olfaction compared to immunity, carbohydrate metabolism and amino-acid metabolism for wild-caught mice and classical laboratory strains, respectively. Using two subspecies of wild-caught Mus musculus, we identified putative CNVs unique to those subspecies and show this diversity is better captured by wild-derived laboratory strains than by the classical laboratory strains. A total of 9 genic copy number variable regions (CNVRs) were selected for experimental confirmation by droplet digital PCR (ddPCR).ConclusionThe analysis we present is a comprehensive, genome-wide analysis of CNVs in Mus musculus, which increases the number of known variants in the species and will accelerate the identification of novel variants in future studies.
Project description:BackgroundLong terminal repeat (LTR) retrotransposons make up a large fraction of the typical mammalian genome. They comprise about 8% of the human genome and approximately 10% of the mouse genome. On account of their abundance, LTR retrotransposons are believed to hold major significance for genome structure and function. Recent advances in genome sequencing of a variety of model organisms has provided an unprecedented opportunity to evaluate better the diversity of LTR retrotransposons resident in eukaryotic genomes.ResultsUsing a new data-mining program, LTR_STRUC, in conjunction with conventional techniques, we have mined the GenBank mouse (Mus musculus) database and the more complete Ensembl mouse dataset for LTR retrotransposons. We report here that the M. musculus genome contains at least 21 separate families of LTR retrotransposons; 13 of these families are described here for the first time.ConclusionsAll families of mouse LTR retrotransposons are members of the gypsy-like superfamily of retroviral-like elements. Several different families of unrelated non-autonomous elements were identified, suggesting that the evolution of non-autonomy may be a common event. High sequence similarity between several LTR retrotransposons identified in this study and those found in distantly-related species suggests that horizontal transfer has been a significant factor in the evolution of mouse LTR retrotransposons.