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Defective T-cell activation is associated with augmented transforming growth factor Beta sensitivity in mice with
1Department of Microbiology, Health Sciences Center, University of Virginia Medical Center, Jordan Hall, Box 800734, Room 7034, Charlottesville, VA 22908, USA. sp3i@virginia.edu
Abstract:
The proto-oncogene Sno has been shown to be a negative regulator of transforming growth factor beta (TGF-beta) signaling in vitro, using overexpression and artificial reporter systems. To examine Sno function in vivo, we made two targeted deletions at the Sno locus: a 5' deletion, with reduced Sno protein (hypomorph), and an exon 1 deletion removing half the protein coding sequence, in which Sno protein is undetectable in homozygotes (null). Homozygous Sno hypomorph and null mutant mice are viable without gross developmental defects. We found that Sno mRNA is constitutively expressed in normal thymocytes and splenic T cells, with increased expression 1 h following T-cell receptor ligation. Although thymocyte and splenic T-cell populations appeared normal in mutant mice, T-cell proliferation in response to activating stimuli was defective in both mutant strains. This defect could be reversed by incubation with either anti-TGF-beta antibodies or exogenous interleukin-2 (IL-2). Together, these findings suggest that Sno-dependent suppression of TGF-beta signaling is required for upregulation of growth factor production and normal T-cell proliferation following receptor ligation. Indeed, both IL-2 and IL-4 levels are reduced in response to anti-CD3 epsilon stimulation of mutant T cells, and transfected Sno activated an IL-2 reporter system in non-T cells. Mutant mouse embryo fibroblasts also exhibited a reduced cell proliferation rate that could be reversed by administration of anti-TGF-beta. Our data provide strong evidence that Sno is a significant negative regulator of antiproliferative TGF-beta signaling in both T cells and other cell types in vivo.
Insights
The proto-oncogene Sno negatively regulates transforming growth factor beta (TGF-beta) signaling. Sno deficiency impairs T-cell proliferation, highlighting its role in immune response regulation.
Area of Science:
- Immunology
- Molecular Biology
- Oncology
Background:
- The proto-oncogene Sno acts as a negative regulator of transforming growth factor beta (TGF-beta) signaling in vitro.
- Understanding Sno's in vivo function is crucial for elucidating its role in cellular processes and disease.
Purpose of the Study:
- To investigate the in vivo function of Sno in T-cell signaling and proliferation.
- To determine if Sno-dependent regulation of TGF-beta signaling is essential for T-cell function.
Main Methods:
- Generation of Sno hypomorphic and null mutant mice through targeted genomic deletions.
- Analysis of T-cell populations, proliferation assays, and cytokine level measurements (IL-2, IL-4).
- In vitro studies using mouse embryo fibroblasts and reporter systems to assess TGF-beta signaling and cell proliferation.
Main Results:
- Sno mutant mice exhibited defective T-cell proliferation in response to activation stimuli.
- T-cell proliferation defects were rescued by anti-TGF-beta antibodies or interleukin-2 (IL-2).
- Reduced IL-2 and IL-4 levels were observed in stimulated T cells from mutant mice, and Sno activated an IL-2 reporter.
Conclusions:
- Sno-dependent suppression of TGF-beta signaling is critical for the upregulation of growth factors and normal T-cell proliferation.
- Sno acts as a significant negative regulator of antiproliferative TGF-beta signaling in T cells and other cell types in vivo.
- These findings implicate Sno in the regulation of immune responses and cell growth.