Cloning and comparative analysis of the human pre-T-cell receptor alpha-chain gene.

Abstract

In immature T cells the T-cell receptor (TCR) 18-chain gene is rearranged and expressed before the TCR a-chain gene. At this stage TCR 18 chain can form disulfide-linked heterodimers with the pre-T-cell receptor a chain (pTa). Using the recently isolated murine pTa cDNA as a probe, we have isolated the human pTa cDNA. The complete nucleotide sequence predicts a mature protein of 282 aa consisting of an extracellular immunoglobulin-like domain, a connecting peptide, a transmembrane region, and a long cytoplasmic tail. Amino acid sequence comparison of human pTa with the mouse pTa molecule reveals high sequence homology in the extracellular as well as the transmembrane region. In contrast, the cytoplasmic region differs in amino acid composition and in length from the murine homologue. The human pTa gene is expressed in immature but not mature T cells and is located at the p2l.2-pl2 region of the short arm of chromosome 6.Intrathymic T-cell development is accompanied by ordered rearrangement of T-cell receptor (TCR) genes as well as by changes in expression of surface markers (1). At a certain developmental stage, CD4-, CD8-, CD3l0w, CD44+, CD25+ T-cell precursors downregulate CD44 expression and begin to rearrange the TCR (3-chain (TCRI3) locus. After productive TCR(3 genes are formed, thymocytes become CD25-, acquire CD4/CD8 coreceptors on the cell surface, and rearrange the TCRa locus (2-5). At the CD4+ CD8+ TCRaf+ stage, thymocytes are subjected to positive and negative selection depending on the quality of TCR-major histocompatibility complex ligand interaction (6, 7). While the TCRao3 controls late thymic development, early developmental steps are controlled by the pre-TCR composed of the variant TCR,3 chain that is disulfide linked to the invariant pre-TCRa (pTa)protein recently described in mice (7-9). The TCRf3-pTa heterodimer is associated with CD3 molecules (10) and 0.250 mg of salmon sperm DNA per ml. Filters were washed in 2x SSC first at room temperature and then at 65°C. The murine cDNA was used as a probe and labeled with

Circulating blood dendritic cells from myeloid leukemia patients display quantitative and cytogenetic abnormalities as well as functional impairment

“…Recently, it has been shown that PDCs in the thymus 20 and human committed DC precursors that are present in adult peripheral blood and thymus 23,25 share with T-cell precursors the expression of pre-T␣ mRNA. 24 We extended these observations by showing that the PDC subset we isolated from leukemic patients expressed pre-T␣ transcript. The finding of a transcript associated with the T-cell differentiation pathway adds support to the putative lymphoid origin of the leukemic PDC subset we have analyzed.…”

“…This phenotypic analysis demonstrated that MDCs and PDCs were phenotypically different from the parental clone (Figure 2A). In addition, as previously described for normal PDCs, 20,[23][24][25] RT-PCR analysis revealed that PDCs isolated from leukemic patients expressed the lymphoid-associated transcript pre-T␣ ( Figure 2B). …”

Human thymus contains IFN-α–producing CD11c–, myeloid CD11c+, and mature interdigitating dendritic cells

“…Because the thymus contains precursor cells capable of giving rise to DCs and to T, B, and NK cells (16,18,19), we investigated in purified thymic DCs the expression of lymphoid-related transcripts. Figure 6a shows that although the three DC subsets lacked CD3γ, CD19, RAG-1, and RAG-2 mRNA, pDCs expressed pre-Tα and λ-like 14.1 mRNA, that are T and B progenitor genes (37,38). Moreover, while searching for pDC specific markers (M.-C. Rissoan, unpublished data), we found a tag sequence corresponding to the Ets family transcription factor Spi-B (39) that has been described as exclusively expressed in lymphoid cells (40).…”

Synergistic Effects of Interleukin-7 and Pre-T Cell Receptor Signaling in Human T Cell Development

“…Moreover, pre-TCR does not require CD3␦ for its function (64). Unlike murine pre-T␣, human pre-T␣ has an endoplasmic reticulum retention signal in its cytoplasmic domain and is strongly associated with the CD3 chain (54,55). We detected abundant pre-T␣ RNA expression in all three T-ALL cell lines, yet surface pre-T␣ was barely detected, and only Molt3 showed increased intracellular pre-T␣ expression.…”

“…Pre-TCR signaling occurs through pathways reminiscent of signaling after TCR ligation in mature T cells based on knock-out and transgenic mouse studies (6, 31, 49 -53). However, critical differences exist between the mouse and human cytoplasmic domains of the pre-T␣ chain (5,25,54,55).…”