Project description:The eye lens is composed of fiber cells, which differentiate from epithelial cells on its anterior surface. In concert with this differentiation, a set of proteins essential for lens function is synthesized, and the cellular organelles are degraded. To understand the molecular mechanism of the lens cell differentiation, we compared the gene expression profiles between epithelial and cortical fiber cells of young mouse lens using a microarray analysis. Keywords: cell-type comparison
Project description:Epithelial cells and differentiated fiber cells represent distinct compartments in the ocular lens. While previous studies have revealed proteins that are preferentially expressed in epithelial vs. fiber cells, a comprehensive proteomics library comparing the molecular composition of epithelial vs. fiber cells is essential for understanding lens formation, function, disease and regenerative potential, and for efficient differentiation of pluripotent stem cells for modeling of lens development and pathology in vitro. To compare protein composition between the lens epithelium and fibers, we employed tandem mass spectrometry (2DLC/ MS) analysis of micro-dissected mouse P0.5 lenses. Functional classifications of the top 525 identified proteins into gene ontology categories by molecular process and subcellular localization, were adapted for lens. Expression levels of both epithelial and fiber proteomes were compared with their temporal and spatial mRNA levels using E14.5, E16.5, E18.5, and P0.5 RNA-Seq data sets. During this developmental time window, multiple complex biosynthetic and catabolic processes generate the molecular and structural foundation for lens transparency. As expected, crystallins showed a high correlation between their mRNA and protein levels. Comprehensive data analysis confirmed and/or predicted roles for transcription factors (TFs), RNA-binding proteins, translational apparatus including ribosomal heterogeneity and initiation factors, microtubules, cytoskeletal and membrane proteins in lens formation and maturation. Our data highlighted many proteins with unknown function in the lens that were preferentially enriched in epithelium or fibers, setting the stage for future studies to further dissect the roles of these proteins in fiber cell differentiation vs. epithelial cell maintenance. In conclusion, the present proteomic datasets established reference mouse lens epithelium and fiber cell proteomes, provided quantitative analyses of protein and RNA-Seq data, and probed the major proteome remodeling required to form the mature lens fiber cells.
Project description:Genome-wide approach to identify the cell-autonomous role of Brg1 in lens fiber cell terminal differentiation. To examine roles of Brg1 in mouse lens development, a dnBrg1 transgenic construct was expressed using the lens-specific alphaA-crystallin promoter in postmitotic lens fiber cells. Morphological studies revealed abnormal lens fiber cell differentiation in transgenic lenses resulting in cataract. Electron microscopic studies showed abnormal lens suture formation and incomplete karyolysis (denucleation) of lens fiber cells. To identify genes regulated by Brg1, RNA expression profiling was performed in E15.5 embryonic wild type and dnBrg1 transgenic lenses. In addition, comparisons between differentially expressed genes in dnBrg1 transgenic, Pax6 heterozygous, and Hsf4 homozygous lenses identified multiple genes co-regulated by Brg1, Hsf4 and Pax6. Among them DNase IIbeta, a key enzyme required for lens fiber cell denucleation, was found downregulated in each of the Pax6, Brg1 and Hsf4 model systems. Lens-specific deletion of Brg1 using conditional gene targeting demonstrated that Brg1 was required for lens fiber cell differentiation and indirectly for retinal development but was not essential for lens lineage formation. Wild type and dnBrg1 transgenic lenses, 4 biological replicates each
Project description:The mature eye lens contains a surface layer of epithelial cells called the lens epithelium that require a functional mitochondrial population to maintain the homeostasis and transparency of the entire lens. The lens epithelium overlies a core of terminally differentiated fiber cells that must degrade their mitochondria to achieve lens transparency. These distinct mitochondrial populations make the lens a useful model system to identify those genes that regulate the balance between mitochondrial homeostasis and elimination. Here we used an RNA sequencing and bioinformatics approach to identify the transcript levels of all genes expressed by distinct regions of the lens epithelium and maturing fiber cells of the embryonic Gallus gallus (chicken) lens. Our analysis detected over 15,000 unique transcripts expressed by the embryonic chicken lens. Of these, over 3000 transcripts exhibited significant differences in expression between lens epithelial cells and fiber cells. Multiple transcripts coding for separate mitochondrial homeostatic and degradation mechanisms were identified to exhibit preferred patterns of expression in lens epithelial cells that require mitochondria relative to lens fiber cells that require mitochondrial elimination. These included differences in the expression levels of metabolic, autophagy, and mitophagy transcripts between lens epithelial cells and lens fiber cells. These data provide a comprehensive window into all genes transcribed by the lens and those mitochondrial regulatory and degradation pathways that function to maintain mitochondrial populations in the lens epithelium and to eliminate mitochondria in maturing lens fiber cells. Differentiation-state transcriptional analysis of embryonic chicken lenses was performed following microdissection of 100 embryonic day 13 (E13) chicken lenses into four distinct regions that represent a continuum of lens cell differentiation states: lens central epithelium (EC), equatorial epithelium (EQ), cortical fibers (FP), and central fibers (FC). Further analysis of the transcriptional content of biologically replicate samples was performed by Illumina directional mRNA sequencing and resulting reads mapped by TopHat and assembled with Cufflinks.
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:Genome-wide approach to identify the cell-autonomous role of Brg1 in lens fiber cell terminal differentiation. To examine roles of Brg1 in mouse lens development, a dnBrg1 transgenic construct was expressed using the lens-specific alphaA-crystallin promoter in postmitotic lens fiber cells. Morphological studies revealed abnormal lens fiber cell differentiation in transgenic lenses resulting in cataract. Electron microscopic studies showed abnormal lens suture formation and incomplete karyolysis (denucleation) of lens fiber cells. To identify genes regulated by Brg1, RNA expression profiling was performed in E15.5 embryonic wild type and dnBrg1 transgenic lenses. In addition, comparisons between differentially expressed genes in dnBrg1 transgenic, Pax6 heterozygous, and Hsf4 homozygous lenses identified multiple genes co-regulated by Brg1, Hsf4 and Pax6. Among them DNase IIbeta, a key enzyme required for lens fiber cell denucleation, was found downregulated in each of the Pax6, Brg1 and Hsf4 model systems. Lens-specific deletion of Brg1 using conditional gene targeting demonstrated that Brg1 was required for lens fiber cell differentiation and indirectly for retinal development but was not essential for lens lineage formation.
Project description:Differential expression of HSF4 in null newborn mouse and wildtype lenses was examined to identify putative downstream targets of HSF4. To examine roles of Brg1 in mouse lens development, a dnBrg1 transgenic construct was expressed using the lens-specific aA-crystallin promoter in postmitotic lens fiber cells. Morphological studies revealed abnormal lens fiber cell differentiation in transgenic lenses resulting in cataract. Electron microscopic studies showed abnormal lens suture formation and incomplete karyolysis (denucleation) of lens fiber cells. To identify genes regulated by Brg1, RNA expression profiling was performed in E15.5 embryonic wild type and dnBrg1 transgenic lenses. In addition, comparisons between differentially expressed genes in dnBrg1 transgenic, Pax6 heterozygous, and Hsf4 homozygous lenses identified multiple genes co-regulated by Brg1, Hsf4 and Pax6. Among them DNase IIb, a key enzyme required for lens fiber cell denucleation, was found downregulated in each of the Pax6, Brg1 and Hsf4 model systems. Lens-specific deletion of Brg1 using conditional gene targeting demonstrated that Brg1 was required for lens fiber cell differentiation and indirectly for retinal development but was not essential for lens lineage formation. Keywords: Differential mRNA Expression Three biological replicate experiments were performed with HSF null and wildtype lenses.
Project description:The lens of the eye is consisted of lens fiber cells that undergo large-scale organelle degradation during terminal differentiation. To understand the molecular mechanism of large-scale organelle degradation, we compared the gene expression profiles between the lens and body without eyes of larval zebrafish using a microarray analysis.
Project description:Chromatin remodeling enzyme Brg1 is required for mouse lens fiber cell terminal differentiation and their denucleation [lens tissue]