Abstract Early hematopoietic progenitors undergo sophisticated developmental processes to become committed progenitors for innate lymphoid cells (ILC) in hematopoietic tissues, which ultimately become mature ILC subsets in the periphery. Basic leucine zipper ATF-like transcription factor (Batf) plays important roles in lymphocyte biology. We report that Batf regulates the production of bone marrow ILC progenitors and maintenance of peripheral ILCs. Batf is most highly expressed in ILCs among all lymphocytes. Data from in vivo and in vitro ILC differentiation experiments revealed that the expression of Batf is induced in early ILC progenitors at the α-lymphoid progenitor stage in response to the cytokine IL-7. Our Chromatin immunoprecipitation and retroviral gene transfer experiments revealed that up-regulated Batf binds and activates transcription of the Nfil3 gene to promote ILC hematopoiesis. Data from bone marrow chimera and parabiosis experiments support that Batf is intrinsically necessary to maintain normal numbers of early and late ILC progenitors in the bone marrow and mature ILC1, ILC2, ILC3, and NK cells in most peripheral tissues. Batf-deficient mice have ILC3 lymphopenia and fail to control Citrobacter rodentium infection. Moreover, ILC2 responses to cytokines were defective in Batf-deficient mice. Thus, Batf is required for normal ILC responses to inflammatory cytokines and bacterial infection. These data suggest that Batf plays fairly comprehensive roles in supporting bone marrow hematopoiesis, maintenance, and effector functions of ILCs.
The active metabolite of vitamin A, retinoic acid, is a key mediator
of balanced immune responses. The major nuclear receptor of retinoic acid,
retinoic receptor alpha (RARα), functions as a transcriptional regulator, with
both active and repressive effects on transcription depending on interactions
with nuclear cofactors dictated by ligand-binding effects on protein
confirmation. While significant advances have been made in understanding the
combined effects of retinoic acid and RARα, the individual roles of each remain
incompletely identified.
Epigenetic
effects of all-trans retinoic acid (At-RA) and RARα on the transcriptome of T
helper cells were assessed using a novel transgenic mouse strain designed to
overexpress RARα in T cells and a conditional knock out strain in which RARα was
specifically deleted from T cells. At-RA and RARα had divergent roles in
promoting Th17 and Treg differentiation, with RARα expression favoring Th17
differentiation over Treg differentiation, and At-RA promoting Treg
differentiation over Th17 differentiation. Transcriptome analysis identified
groups of At-RA and RARα differentially regulated genes (DEGs). Comparison of
these genes to the H3k27 acetylated and tri-methylated epigenetic modifications
demonstrated that RARα expression increased the overall level of these
epigenetic modifications in all DEG groups, with enhanced control of
transcriptional regulation mediated by higher RARα expression. Additionally, expression
of transcriptional repressors was
strongly regulated by At-RA in a RARα-dependent manner and had repressive
effects on the differentiation of T helper cells. Immunometabolism
was also enhanced by RARα expression, leading us to study potential non-genomic
roles of RARα on signaling pathways. The major TCR signaling pathways were
enhanced by RARα but suppressed by At-RA, suggesting a mechanism by which RARα
regulates cellular metabolism upon T cell activation. In summary,
we identified distinct epigenetic and non-genomic effects of RARα as novel
regulatory mechanisms by which vitamin A and retinoic acid influence immune
responses. Further research into these findings, notably RARα involvement in
signal transduction pathways of immune cells, will define how this research can
be translated into clinically-relevant applications.
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Early hematopoietic progenitors undergo sophisticated developmental processes to become committed innate lymphoid cell (ILC) progenitors and ultimately mature ILC subsets in the periphery. Basic leucine zipper ATF-like transcription factor (Batf) plays important roles in lymphocyte biology. We report here that Batf regulates the production of bone marrow ILC progenitors and maintenance of peripheral ILCs. The expression of Batf is induced during ILC development at the α-lymphoid progenitor stage in response to the cytokine IL-7. As a potential mechanism, up-regulated Batf binds and activates transcription of the
DNA damage often induces heterogeneous cell-fate responses, such as cell-cycle arrest and apoptosis. Through single-cell RNA sequencing (scRNA-seq), we characterize the transcriptome response of cultured colon cancer cell lines to 5-fluorouracil (5FU)-induced DNA damage. After 5FU treatment, a single population of colon cancer cells adopts three distinct transcriptome phenotypes, which correspond to diversified cell-fate responses: apoptosis, cell-cycle checkpoint, and stress resistance. Although some genes are regulated uniformly across all groups of cells, many genes showed group-specific expression patterns mediating DNA damage responses specific to the corresponding cell fate. Some of these observations are reproduced at the protein level by flow cytometry and are replicated in cells treated with other 5FU-unrelated genotoxic drugs, camptothecin and etoposide. This work provides a resource for understanding heterogeneous DNA damage responses involving fractional killing and chemoresistance, which are among the major challenges in current cancer chemotherapy.
Abstract Vitamin A and its biologically active metabolites, all-trans and 9-cis retinoic acid (RA), are thought to be important in generating and modulating immune function. However, RA modulates the function of many types of immune cells, and its specific role in dendritic cell (DC) activation, Ag presentation, and T cell effector function has not been fully characterized. Because RA works primarily through RA receptor (RAR)α, we examined mice with a myeloid cell–specific defect in RA signaling. These transgenic mice have a CD11c-cre–driven expression of a truncated form of RARα that specifically blocks the signaling of all forms of RARs in myeloid cells. This defect results in abnormal DC function, with impaired DC maturation and activation, and reduced Ag uptake and processing. These DC abnormalities were associated with a reduced ability to mount Ag-specific T cell responses to immunization despite having normally functioning T cells. In contrast, the loss of DC-specific RA signaling did not significantly alter levels of Ag-specific Abs postimmunization and resulted in an increase in bronchial IgA. Our findings indicate that RA signaling in DCs is crucial for immune activation, and its absence impairs the development of Ag-specific effector functions of T cell immunity.
Langerhans cells (LC) are the prototype langerin-expressing dendritic cells (DC) that reside specifically in the epidermis, but langerin-expressing conventional DCs also reside in the dermis and other tissues, yet the factors that regulate their development are unclear. Because retinoic acid receptor alpha (RARα) is highly expressed by LCs, we investigate the functions of RARα and retinoic acid (RA) in regulating the langerin-expressing DCs. Here we show that the development of LCs from embryonic and bone marrow-derived progenitors and langerin+ conventional DCs is profoundly regulated by the RARα-RA axis. During LC differentiation, RARα is required for the expression of a LC-promoting transcription factor Runx3, but suppresses that of LC-inhibiting C/EBPβ. RARα promotes the development of LCs and langerin+ conventional DCs only in hypo-RA conditions, a function effectively suppressed at systemic RA levels. Our findings identify positive and negative regulatory mechanisms to tightly regulate the development of the specialized DC populations.
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