Transcriptional activity of the 5′-flanking region of the thyroid transcription factor-1 gene in human thyroid cell lines

Thyroid transcription factor-1 (TTF-1, NKX2-1) is a homeodomain-containing transcriptional factor that binds to and activates the promoters of thyroid and lung-specific genes, such as thyroglobulin, thyroid peroxidase, and thyroid stimulating hormone receptor. TTF-1 is known to play a key role in the development of the thyroid. However, the precise mechanism of TTF-1 gene transcription in human thyroid cells has not been studied. The expression of transcriptional activity in various lengths of the 5′-flanking region of the human TTF -1 gene was studied in TTF-1 positive and negative human thyroid cell lines. Increased transcriptional activity was observed in thyroid cell lines containing plasmids that coded for a sequence proximal to the transcription start site of exon 1 of the TTF-1 gene. However, we did not observe any difference in promoter activity in the region up to −2.6 kb from the proximal transcription start site of the TTF-1 gene between TTF-1 positive and negative cells. These results suggest that the proximal 5′-flanking region of the human TTF -1 gene does not contain sufficient cis-active regulatory information to direct gene expression in thyroid cells, and that other cis- or trans-acting factors participate in the thyroid specific gene expression of TTF-1

MicroRNA 10a Marks Regulatory T Cells

MicroRNAs (miRNAs) are crucial for regulatory T cell (Treg) stability and function. We report that microRNA-10a (miR-10a) is expressed in Tregs but not in other T cells including individual thymocyte subsets. Expression profiling in inbred mouse strains demonstrated that non-obese diabetic (NOD) mice with a genetic susceptibility for autoimmune diabetes have lower Treg-specific miR-10a expression than C57BL/6J autoimmune resistant mice. Inhibition of miR-10a expression in vitro leads to reduced FoxP3 expression levels and miR-10a expression is lower in unstable “exFoxP3” T cells. Unstable in vitro TGF-ß-induced, iTregs do not express miR-10a unless cultured in the presence of retinoic acid (RA) which has been associated with increased stability of iTreg, suggesting that miR-10a might play a role in stabilizing Treg. However, genetic ablation of miR-10a neither affected the number and phenotype of natural Treg nor the capacity of conventional T cells to induce FoxP3 in response to TGFβ, RA, or a combination of the two. Thus, miR-10a is selectively expressed in Treg but inhibition by antagomiRs or genetic ablation resulted in discordant effects on FoxP3

TGF-beta signaling in thymic epithelial cells regulates thymic involution and postirradiation reconstitution.

The thymus constitutes the primary lymphoid organ responsible for the generation of naive T cells. Its stromal compartment is largely composed of a scaffold of different subsets of epithelial cells that provide soluble and membrane-bound molecules essential for thymocyte maturation and selection. With senescence, a steady decline in the thymic output of T cells has been observed. Numeric and qualitative changes in the stromal compartment of the thymus resulting in reduced thymopoietic capacity have been suggested to account for this physiologic process. The precise cellular and molecular mechanisms underlying thymic senescence are, however, only incompletely understood. Here, we demonstrate that TGF-beta signaling in thymic epithelial cells exerts a direct influence on the cell's capacity to support thymopoiesis in the aged mouse as the physiologic process of thymic senescence is mitigated in mice deficient for the expression of TGF-beta RII on thymic epithelial cells. Moreover, TGF-beta signaling in these stromal cells transiently hinders the early phase of thymic reconstitution after myeloablative conditioning and hematopoietic stem cell transplantation. Hence, inhibition of TGF-beta signaling decelerates the process of age-related thymic involution and may hasten the reconstitution of regular thymopoiesis after hematopoietic stem cell transplantation

Identification of MiR-205 As a MicroRNA That is highly expressed in medullary thymic epithelial cells

© 2015 Khan et al.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 del

Stabilized beta-catenin in thymic epithelial cells blocks thymus development and function.

Thymic T cell development is dependent on a specialized epithelial microenvironment mainly composed of cortical and medullary thymic epithelial cells (TECs). The molecular programs governing the differentiation and maintenance of TECs remain largely unknown. Wnt signaling is central to the development and maintenance of several organ systems but a specific role of this pathway for thymus organogenesis has not yet been ascertained. In this report, we demonstrate that activation of the canonical Wnt signaling pathway by a stabilizing mutation of beta-catenin targeted exclusively to TECs changes the initial commitment of endodermal epithelia to a thymic cell fate. Consequently, the formation of a correctly composed and organized thymic microenvironment is prevented, thymic immigration of hematopoietic precursors is restricted, and intrathymic T cell differentiation is arrested at a very early developmental stage causing severe immunodeficiency. These results suggest that a precise regulation of canonical Wnt signaling in thymic epithelia is essential for normal thymus development and function

DGCR8-Mediated Production of Canonical Micrornas Is Critical for Regulatory T Cell Function and Stability

Regulatory T cells (Treg) are integral for immune homeostasis. Here we demonstrate that canonical microRNAs (miRNAs) are required for Treg function because mice with DGCR8-deficient Treg cells spontaneously develop a scurfy-like disease. Using genetic lineage marking we show that absence of miRNAs leads to reduced FoxP3 expression in Treg cells in vivo. In vitro culture of purified DGCR8-deficient Treg leads to a loss of FoxP3 expression. We conclude that canonical miRNAs are essential to maintain stable FoxP3 expression and Treg function. Thus, signals interfering with miRNA homeostasis might contribute to autoimmune diseases