Project description:PURPOSE: To provide a detailed gene expression profile of the normal postnatal mouse cornea. METHODS: Serial analysis of gene expression (SAGE) was performed on postnatal day (PN)9 and adult mouse (6 week) total corneas. The expression of selected genes was analyzed by in situ hybridization. RESULTS: A total of 64,272 PN9 and 62,206 adult tags were sequenced. Mouse corneal transcriptomes are composed of at least 19,544 and 18,509 unique mRNAs, respectively. One third of the unique tags were expressed at both stages, whereas a third was identified exclusively in PN9 or adult corneas. Three hundred thirty-four PN9 and 339 adult tags were enriched more than fivefold over other published nonocular libraries. Abundant transcripts were associated with metabolic functions, redox activities, and barrier integrity. Three members of the Ly-6/uPAR family whose functions are unknown in the cornea constitute more than 1% of the total mRNA. Aquaporin 5, epithelial membrane protein and glutathione-S-transferase (GST) omega-1, and GST alpha-4 mRNAs were preferentially expressed in distinct corneal epithelial layers, providing new markers for stratification. More than 200 tags were differentially expressed, of which 25 mediate transcription. CONCLUSIONS: In addition to providing a detailed profile of expressed genes in the PN9 and mature mouse cornea, the present SAGE data demonstrate dynamic changes in gene expression after eye opening and provide new probes for exploring corneal epithelial cell stratification, development, and function and for exploring the intricate relationship between programmed and environmentally induced gene expression in the cornea. Keywords: other
Project description:Thymic epithelial cells (TECs) support T cell development in the thymus. Cortical thymic epithelial cells (cTECs) facilitate positive selection of developing thymocytes whereas medullary thymic epithelial cells (mTECs) facilitate the deletion of self-reactive thymocytes in order to prevent autoimmunity. The mTEC compartment is highly dynamic with continuous maturation and turnover, but the genetic regulation of these processes remains poorly understood. MicroRNAs (miRNAs) are important regulators of TEC genetic programs since miRNA-deficient TECs are severely defective. However, the individual miRNAs important for TEC maintenance and function and their mechanisms of action remain unknown. Here, we demonstrate that miR-205 is highly and preferentially expressed in mTECs during both thymic ontogeny and in the postnatal thymus. This distinct expression is suggestive of functional importance for TEC biology. Genetic ablation of miR-205 in TECs, however, neither revealed a role for miR-205 in TEC function during homeostatic conditions nor during recovery from thymic stress conditions. Thus, despite its distinct expression, miR-205 on its own is largely dispensable for mTEC biology. In order to identify miRNAs differentially expressed in mTECs, we purified cortical thymic epithelial cells (cTECs), mTECs and CD45+ cells as three distinct populations and prepared RNA for microarray analysis. Thymic subsets were FACS-purified from 4-week old NOD wildtype mice. Thymi from 10-12 female mice were pooled together for stromal cell isolation for a total of 3 CD45+, 2 cTEC and 3 mTEC biologic replicates.
Project description:Genetic modeling of thymic involution has demonstrated the importance of individual inflammatory pathways affecting the thymic microenvironment, particularly thymic epithelial cells (TEC). We studied the pathogenic processes in chronological aging of the murine thymus. We used microarrays to elucidate the global gene expression and to identify a leading edge subset of age-associated genes in TEC. Analyses of the TEC transcriptome demonstrated altered expression associated with inflammatory and fatty acid metabolism.
Project description:T cell differentiation is governed by interactions with thymic epithelial cells (TECs) and defects in this process undermine immune function and tolerance. To uncover new strategies to restore thymic function and adaptive immunity in immunodeficiency, we sought to determine the molecular mechanisms that control life and death decisions in TEC. We created a mouse model which specifically deleted the pro-survival gene Mcl1 in TEC. We found that while BCL-2 and BCL-XL were dispensable for TEC homeostasis, MCL-1 deficiency impacted on TEC as early as E15.5, resulting in early thymic atrophy and T cell lymphopenia, with near complete loss of thymic tissue by 2 months of age. MCL-1 was not necessary for TEC differentiation but was continually required for the survival of medullary TEC, including autoimmune regulator (AIRE) expressing TECs and the maintenance of overall thymic architecture. To understand the molecular mechanisms in more detail, RNA-seq profiling was undertaken of cortical and medullary thymic epithelial cells (cTECs and mTECs) from wildtype and knockout mice.
Project description:The transcription factor FOXN1 is a master regulator of thymic epithelial cell development and function. Here we demonstrate that FOXN1 expression is differentially regulated during organogenesis and participates in multi-molecular nuclear condensates essential for the factor's transcriptional activity. FOXN1's C-terminal sequence regulates the diffusion velocity within these aggregates and modulates the binding to proximal gene regulatory regions. These dynamics are significantly altered in a patient's FOXN1 mutant modified in its C-terminal sequence. This mutant is transcriptionally inactive and acts as a dominant negative factor displacing wild-type FOXN1 from condensates and causing athymia and severe lymphopenia in heterozygotes. Expression of the mutated mouse ortholog, Foxn1, selectively impairs mouse thymic epithelial cell (TEC) differentiation, revealing a gene dose dependency for individual TEC subtypes. We have therefore identified the cause for a primary immunodeficiency disease and determined the mechanism by which this FOXN1 gain-of-function mutant mediates its dominant negative effect.
Project description:Thymic epithelial cells (TEC) control T cell development and play essential roles in establishing self-tolerance. Transcription factors controlling TEC development are poorly characterized. We report that Klf6 plays a critical role in TEC development. Mice deficient for Klf6 in TEC had a hypoplastic thymus - evident from fetal stages into adulthood. Proliferation of TEC was not reduced, but a dramatic increase in the frequency of apoptotic TEC in fetal and adult thymus was observed. Among cortical TEC (cTEC), we found expansion of a previously unreported cTEC population expressing the transcription factor Sox10. Medullary TEC (mTEC) subsets were not equally impacted with Ccl21a+ mTEC I and Tuft-like mTEC IV being disproportionately affected. Consistent with these TEC defects, naïve conventional T cells and NKT cells were reduced in the spleen, and signs of autoimmunity were evident. Thus, Klf6 has a pro- survival role in TEC and is also required for differentiation of the mTEC I and mTEC IV populations of TEC in adult mice. In this work, we report that mice with Foxn1-Cre mediated ablation of Klf6 in TEC demonstrate thymic hypoplasia beginning from prenatal life and extending through adulthood. Guided by single-cell transcriptional profiling, we determined that loss of Klf6 increased programmed cell death of TEC in prenatal and adult mice. In adult mice, thymic Klf6 deficiency severely impacted the mTEC I and mTEC IV populations. In addition, Klf6 deficiency led to the expansion of a previously uncharacterized cTEC population expressing Sox10 that is present in wild-type mice at very low frequencies. We observed concordant reductions of the naïve αβ T cell and iNKT pools in the periphery of young adult mice. Furthermore, we detected T cell infiltration in salivary and lacrimal glands, indicating defects in T cell tolerance.
Project description:Thymic epithelial cells (TEC) control T cell development and play essential roles in establishing self-tolerance. Transcription factors controlling TEC development are poorly characterized. We report that Klf6 plays a critical role in TEC development. Mice deficient for Klf6 in TEC had a hypoplastic thymus - evident from fetal stages into adulthood. Proliferation of TEC was not reduced, but a dramatic increase in the frequency of apoptotic TEC in fetal and adult thymus was observed. Among cortical TEC (cTEC), we found expansion of a previously unreported cTEC population expressing the transcription factor Sox10. Medullary TEC (mTEC) subsets were not equally impacted with Ccl21a+ mTEC I and Tuft-like mTEC IV being disproportionately affected. Consistent with these TEC defects, naïve conventional T cells and NKT cells were reduced in the spleen, and signs of autoimmunity were evident. Thus, Klf6 has a pro- survival role in TEC and is also required for differentiation of the mTEC I and mTEC IV populations of TEC in adult mice. In this work, we report that mice with Foxn1-Cre mediated ablation of Klf6 in TEC demonstrate thymic hypoplasia beginning from prenatal life and extending through adulthood. Guided by single-cell transcriptional profiling, we determined that loss of Klf6 increased programmed cell death of TEC in prenatal and adult mice. In adult mice, thymic Klf6 deficiency severely impacted the mTEC I and mTEC IV populations. In addition, Klf6 deficiency led to the expansion of a previously uncharacterized cTEC population expressing Sox10 that is present in wild-type mice at very low frequencies. We observed concordant reductions of the naïve αβ T cell and iNKT pools in the periphery of young adult mice. Furthermore, we detected T cell infiltration in salivary and lacrimal glands, indicating defects in T cell tolerance.