The Ets family of transcription factors have been suggested to function as key regulators of hematopoeisis. Here we describe aberrant hematopoeisis and hemorrhaging in mouse embryos homozygous for a targeted disruption in the Ets family member, Fli1. Mutant embryos are found to hemorrhage from the dorsal aorta to the lumen of the neural tube and ventricles of the brain (hematorrhachis) on embryonic day 11.0 (E11.0) and are dead by E12.5. Histological examinations and in situ hybridization reveal disorganization of columnar epithelium and the presence of hematomas within the neuroepithelium and disruption of the basement membrane lying between this and mesenchymal tissues, both of which express Fli1 at the time of hemorrhaging. Livers from mutant embryos contain few pronormoblasts and basophilic normoblasts and have drastically reduced numbers of colony forming cells. These defects occur with complete penetrance of phenotype regardless of the genetic background (inbred B6, hybrid 129/B6, or outbred CD1) or the targeted embryonic stem cell line used for the generation of knockout lines. Taken together, these results provide in vivo evidence for the role of Fli1 in the regulation of hematopoiesis and hemostasis.The human FLI1 gene, which we originally cloned from the leukemia T-cell line, CEM, is a member of the Ets gene family of transcription factors (38). As observed with all other members of the Ets gene family, FLI1 encodes a protein that retains a region of conserved sequence, the Ets domain (37, 38). This minimal 85-amino-acid region has been shown to be the DNAbinding domain. Ets proteins bind to DNA sequences that contain a consensus GGA(A/T) core motif (Ets-binding site) and, in the majority of cases, function as transcriptional activators. Ets proteins control the expression of genes that are critical for the control of cellular proliferation, differentiation, and programmed cell death. The presence of multiple Ets family proteins in a variety of cell types and the overlapping DNA-binding specificity of the Ets proteins have made it difficult to identify target genes that are specific for individual Ets factors. The generation and analysis of targeted disruptions in individual family members, coupled with the identification of such target genes, however, is one approach to understanding the role of Ets transcription factors in normal and dysregulated development. A variety of studies including the analysis of expression of members of the Ets transcription factor family in hematopoietic tissues and cell lines and the generation and analysis of targeted mutations in Ets gene family members in mouse suggest that they play important roles in the regulation of normal hematopoietic development (13,14,29).FLI1 was found to be highly related to the human ERG gene, and we originally named it ERGB to reflect this homology (38). Sequence alignments of the predicted 452-amino-acid protein product of human FLI1 with those of the ERG and mouse Fli1 products (5) demonstrated 80 and 96% similarity, respectively. FLI1 ha...
Mutations in the SLC26A3 (DRA (down-regulated in adenoma)) gene constitute the molecular etiology of congenital chloride-losing diarrhea in humans. To ascertain its role in intestinal physiology, gene targeting was used to prepare mice lacking slc26a3. slc26a3-deficient animals displayed postpartum lethality at low penetrance. Surviving dra-deficient mice exhibited high chloride content diarrhea, volume depletion, and growth retardation. In addition, the large intestinal loops were distended, with colonic mucosa exhibiting an aberrant growth pattern and the colonic crypt proliferative zone being greatly expanded in slc26a3-null mice. Apical membrane chloride/base exchange activity was sharply reduced, and luminal content was more acidic in slc26a3-null mouse colon. The epithelial cells in the colon displayed unique adaptive regulation of ion transporters; NHE3 expression was enhanced in the proximal and distal colon, whereas colonic H,K-ATPase and the epithelial sodium channel showed massive up-regulation in the distal colon. Plasma aldosterone was increased in slc26a3-null mice. We conclude that slc26a3 is the major apical chloride/base exchanger and is essential for the absorption of chloride in the colon. In addition, slc26a3 regulates colonic crypt proliferation. Deletion of slc26a3 results in chloride-rich diarrhea and is associated with compensatory adaptive up-regulation of ion-absorbing transporters.The SLC26A3 or DRA (down-regulated in adenoma) gene was originally identified in a subtractive hybridization screen comparing the mRNAs expressed in colon cancer and normal colon tissue (1). DRA is expressed in normal colonic epithelium, but is absent or reduced in adenomas and adenocarcinomas (1). Subsequent studies identified SLC26A3 (DRA) as a member of a large conserved family of anion exchangers (SLC26) that encompass at least 10 distinct genes (2-20). Except for SLC26A5 (prestin), all function as anion exchangers with versatility with respect to transported anions (2-20). Immunohistochemical studies localized SLC26A3 on the apical membrane of colonic mucosa, with lower levels in the small intestine (4, 25). In humans, SLC26A3 encodes a 764-amino acid protein and is located on chromosome 7 in a head-to-tail arrangement with SLC26A4 (pendrin), indicating ancient gene duplication.Genetic analysis studies linked mutations in DRA (SLC26A3) to congenital chloride-losing diarrhea (CLD 5 ; OMIM accession number 214700), a disease manifested by enhanced chloride loss in the stool and volume depletion (4). Functional studies in vitro have demonstrated that SLC26A3 can mediate multiple anion exchange modes, including Cl Ϫ /HCO 3 Ϫ , Cl Ϫ /oxalate, and Cl Ϫ /hydroxyl, and possibly sulfate/hydroxyl exchanges (6, 21-26). Similar anion exchange activities have been described previously in apical membranes of the colon (27, 28), the site of abundant DRA expression.To initiate an investigation into the role of DRA in an in vivo model, we created slc26a3 (dra) gene-targeted mice that are null for expression of the slc2...
Increased Fli-1 mRNA is present in PBLs from systemic lupus erythematosus patients, and transgenic overexpression of Fli-1 in normal mice leads to a lupus-like disease. We report in this study that MRL/lpr mice, an animal model of systemic lupus erythematosus, have increased splenic expression of Fli-1 protein compared with BALB/c mice. Using mice with targeted gene disruption, we examined the effect of reduced Fli-1 expression on disease development in MRL/lpr mice. Complete knockout of Fli-1 is lethal in utero. Fli-1 protein expression in heterozygous MRL/lpr (Fli-1+/−) mice was reduced by 50% compared with wild-type MRL/lpr (Fli-1+/+) mice. Fli-1+/− MRL/lpr mice had significantly decreased serum levels of total IgG and anti-dsDNA Abs as disease progressed. Fli-1+/− MRL/lpr mice had significantly increased splenic CD8+ and naive T cells compared with Fli-1+/+ MRL/lpr mice. Both in vivo and in vitro production of MCP-1 were significantly decreased in Fli-1+/− MRL/lpr mice. The Fli-1+/− mice had markedly decreased proteinuria and significantly lower pathologic renal scores. At 48 wk of age, survival was significantly increased in the Fli-1+/− MRL/lpr mice, as 100% of Fli-1+/− MRL/lpr mice were alive, in contrast to only 27% of Fli-1+/+ mice. These findings indicate that Fli-1 expression is important in lupus-like disease development, and that modulation of Fli-1 expression profoundly decreases renal disease and improves survival in MRL/lpr mice.
Alveolar epithelial cells are directly exposed to acute and chronic fluctuations in alveolar oxygen tension. Previously, we found that the oxygen-binding protein hemoglobin is expressed in alveolar Type II cells (ATII). Here, we report that ATII cells also express a number of highly specific transcription factors and other genes normally associated with hemoglobin biosynthesis in erythroid precursors. Because hypoxia-inducible factors (HIFs) were shown to play a role in hypoxia-induced changes in ATII homeostasis, we hypothesized that the hypoxia-induced increase in intracellular HIF exerts a concomitant effect on ATII hemoglobin expression. Treatment of cells from the ATII-like immortalized mouse lung epithelial cell line-15 (MLE-15) with hypoxia for 20 hours resulted in dramatic increases in cellular levels of HIF-2a protein and parallel significant increases in hemoglobin messenger RNA (mRNA) and protein expression, as compared with that of control cells cultured in normoxia. Significant increases in the mRNA of globin-associated transcription factors were also observed, and RNA interference (RNAi) experiments demonstrated that the expression of hemoglobin is at least partially dependent on the cellular levels of globin-associated transcription factor isoform 1 (GATA-1). Conversely, levels of prosurfactant proteins B and C significantly decreased in the same cells after exposure to hypoxia. The treatment of MLE-15 cells cultured in normoxia with prolyl 4-hydroxylase inhibitors, which mimic the effects of hypoxia, resulted in increases of hemoglobin and decreases of surfactant proteins. Taken together, these results suggest a relationship between hypoxia, HIFs, and the expression of hemoglobin, and imply that hemoglobin may be involved in the oxygen-sensing pathway in alveolar epithelial cells.Keywords: hemoglobin; alveolar epithelial cells; hypoxia; hypoxiainducible factor Pulmonary hypoxia occurs under both physiologic and pathologic conditions. In fact, a hypoxic environment is necessary for proper embryonic lung development, by promoting the formation of microvasculature and epithelial branching morphogenesis (the average fetal blood O 2 fraction is z2-5%) (1-3). However, postnatal decreases in alveolar oxygen tension as a result of pulmonary disease disrupt alveolar homeostasis. High-altitude ascent, pathologic conditions resulting in inadequate respiration, pulmonary edema after acute lung injury, or congestive heart failure may all result in decreased oxygen tension. Alveolar Type II (ATII) cells represent approximately two thirds of epithelial cell numbers, and are of special clinical interest because of their role in the production, secretion, and recycling of pulmonary surfactant (4). In addition, ATII cells differentiate into Type I (ATI ) cells upon epithelial injury, and also act to clear fluid from the alveolar space. Although numerous studies evaluated the effects of hypoxia on the pulmonary endothelium, few sought to identify hypoxia-regulated genes in alveolar epithelial cells.Our previous stu...
Neurulation is a complex process of histogenesis involving the precise temporal and spatial organization of gene expression. Genes influencing neurulation include proneural genes determining primary cell fate, neurogenic genes involved in lateral inhibition pathways and genes controlling the frequency of mitotic events. This is reflected in the aetiology and genetics of human and mouse neural tube defects, which are of both multifactorial and multigenic origin. The X-linked gene Nap1l2, specifically expressed in neurons, encodes a protein that is highly similar to the nucleosome assembly (NAP) and SET proteins. We inactivated Nap1l2 in mice by gene targeting, leading to embryonic lethality from mid-gestation onwards. Surviving mutant chimaeric embryos showed extensive surface ectoderm defects as well as the presence of open neural tubes and exposed brains similar to those observed in human spina bifida and anencephaly. These defects correlated with an overproduction of neuronal precursor cells. Protein expression studies showed that the Nap1l2 protein binds to condensing chromatin during S phase and in apoptotic cells, but remained cytoplasmic during G1 phase. Nap1l2 therefore likely represents a class of tissue-specific factors interacting with chromatin to regulate neuronal cell proliferation.
Fli-1 belongs to the Ets transcription factor family and is expressed primarily in hematopoietic cells, including most cells active in immunity. To assess the role of Fli-1 in lymphocyte development in vivo, we generated mice that express a truncated Fli-1 protein, lacking the C-terminal transcriptional activation domain (Fli-1ΔCTA). Fli-1ΔCTA/Fli-1ΔCTA mice had significantly fewer splenic follicular B cells, and an increased number of transitional and marginal zone B cells, compared with wild-type controls. Bone marrow reconstitution studies demonstrated that this phenotype is the result of lymphocyte intrinsic effects. Expression of Igα and other genes implicated in B cell development, including Pax-5, E2A, and Egr-1, are reduced, while Id1 and Id2 are increased in Fli-1ΔCTA/Fli-1ΔCTA mice. Proliferation of B cells from Fli-1ΔCTA/Fli-1ΔCTA mice was diminished, although intracellular Ca2+ flux in B cells from Fli-1ΔCTA/Fli-1ΔCTA mice was similar to that of wild-type controls after anti-IgM stimulation. Immune responses and in vitro class switch recombination were also altered in Fli-1ΔCTA/Fli-1ΔCTA mice. Thus, Fli-1 modulates B cell development both centrally and peripherally, resulting in a significant impact on the in vivo immune response.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.