Disruption of thymocyte development and lymphomagenesis induced by SV4O T-antigen

Abstract

The lck gene encodes a membrane-associated protein tyrosine kinase that is expressed specifically in lymphoid cells, especially thymocytes. Structural analysis of the murine and human lck genes previously identified conserved 5' flanking sequences that were proposed to represent transcriptional regulatory elements. Here we demonstrate that a murine lck promoter construct containing these sequences directs the expression of the SV40 T-antigen gene in lymphoid cells. Remarkably, expression of SV40 T-antigen in transgenic animals dramatically disturbs thymic development, resulting in preferential loss of CD4+CD8+ thymocytes. In contrast, immature cells lacking both CD4 and CD8 markers are present in near-normal numbers. Thus SV40 T-antigen expression appears partially to arrest thymopoiesis. Mice bearing the lck-SV40 transgene develop readily explantable thymic tumors at 12-18 weeks of age. Fluorocytometric analyses of lck-SV40 tumor cells reveal that immature thymocytes are frequently immortalized. The lck-SV40 mouse may therefore provide materials for the in vitro investigation of thymocyte differentiation.

Transgenic Expression of Stromal Cell-Derived Factor-1/CXC Chemokine Ligand 12 Enhances Myeloid Progenitor Cell Survival/Antiapoptosis In Vitro in Response to Growth Factor Withdrawal and Enhances Myelopoiesis In Vivo

“…SDF-1/ CXCL12 as well as other chemokines are known to mediate their chemotactic effects for myeloid progenitors and other more mature cells through G ␣i proteins (5)(6)(7)(8)21). To establish additional controls for the enhanced survival of RSV-SDF-1/CXCL12 transgenic myeloid progenitors, we tested the survival of bone marrow and spleen cells from other transgenic mice we produced in which SDF-1/CXCL12 transgene expression was under the control of an LCK promoter (30), which limited expression of the SDF-1/ CXCL12 transgene to lymphoid cells (data not shown). LCK-SDF-1/CXCL12 transgene expression was confirmed by RT-PCR analysis in thymus, lymph nodes, and spleen, but not bone marrow or liver.…”

Down-Regulation of p27Kip1 Expression Is Required for Development and Function of T Cells

“…However, the biological importance of the physiological down-regulation of p27 Kip1 expression in the T cell lineage was not clarified by characterization of these p27 Ϫ/Ϫ mice. We have therefore generated transgenic mice in which p27 is specifically expressed in the T cell lineage under the control of the proximal promoter of the lck gene (28,29) and have analyzed the differentiation, proliferation, and immunoresponses of T cells in these animals. We now show that forced expression of p27 Kip1 in the T cell lineage resulted in developmental arrest of T cells and impairment of T cell-dependent immune responses.…”

“…The PCR product was digested with BamHI and inserted into the BamHI site of the T cell lineage-specific expression vector p1017 containing the proximal promoter of mouse lck followed by the exons, introns, and polyadenylation signal of the human growth hormone (hGH) gene (28,29).…”

Caspase Enzyme Activity Is Not Essential for Apoptosis During Thymocyte Development

“…Transgenic mice were generated and propagated as described previously (27). For studies of negative selection or early thymocyte development, lck-p35 mice were also crossed with OT1 (28) or HY TCR transgenic mice (29) or rag1 Ϫ/Ϫ mice (purchased from The Jackson Laboratory, Bar Harbor, ME) (30), respectively.…”