Isolation and chromosomal localization of a novel human G-protein-coupled receptor (GPR3) expressed predominantly in the central nervous system

Degenerate oligonucleotide primers designed against known G-protein-coupled receptors were used in polymerase chain reaction amplification to isolate a novel receptor sequence (R4) from a rat insulinoma cell line and its human homolog (GPR3) from a human neuroblastoma cDNA library. The novel human receptor sequence is expressed in low abundance predominantly in the central nervous system and at low levels in the lung and kidney. The gene encoding GPR3 is intronless within the coding region, contains at least one intron in the 5'-untranslated region, and has been localized to chromosome 1p34.3. The activating ligand for the homologous receptors R4 and GPR3 is not known, but sequence similarity with the closely related orphan rat receptor R334 [FEBS Lett. 292:243 (1991)] suggests that R334 and the homologous receptors R4 and GPR3 probably represent two discrete molecular subtypes that interact with the same or closely related ligands.

Low serum thyrotropin concentrations as a risk factor for atrial fibrillation in older persons

BACKGROUND

Low serum thyrotropin concentrations are a sensitive indicator of hyperthyroidism but can also occur in persons who have no clinical manifestations of the disorder. We studied whether low serum thyrotropin concentrations in clinically euthyroid older persons are a risk factor for subsequent atrial fibrillation.

METHODS

We studied 2007 persons (814 men and 1193 women) 60 years of age or older who did not have atrial fibrillation in order to determine the frequency of this arrhythmia during a 10-year follow-up period. The subjects were classified according to their serum thyrotropin concentrations: those with low values (< or = 0.1 mU per liter; 61 subjects); those with slightly low values (> 0.1 to 0.4 mU per liter; 187 subjects); those with normal values (> 0.4 to 5.0 mU per liter; 1576 subjects); and those with high values (> 5.0 mU per liter; 183 subjects).

RESULTS

During the 10-year follow-up period, atrial fibrillation occurred in 13 persons with low initial values for serum thyrotropin, 23 with slightly low values, 133 with normal values, and 23 with high values. The cumulative incidence of atrial fibrillation at 10 years was 28 percent among the subjects with low serum thyrotropin values (< or = 0.1 mU per liter), as compared with 11 percent among those with normal values; the age-adjusted incidence of atrial fibrillation was 28 per 1000 person-years among those with low values and 10 per 1000 person-years among those with normal values (P = 0.005). After adjustment for other known risk factors, the relative risk of atrial fibrillation in elderly subjects with low serum thyrotropin concentrations, as compared with those with normal concentrations, was 3.1 (95 percent confidence interval, 1.7 to 5.5; P < 0.001). The 10-year incidence of atrial fibrillation in the groups with slightly low and high serum thyrotropin values was not significantly different from that in the group with normal values.

CONCLUSIONS

Among people 60 years of age or older, a low serum thyrotropin concentration is associated with a threefold higher risk that atrial fibrillation will develop in the subsequent decade.

Impact of transjugular intrahepatic portosystemic shunt on orthotopic liver transplantation

Transjugular intrahepatic portosystemic shunt (TIPS) is being increasingly utilized prior to liver transplantation for portal hypertensive bleeding refractory to sclerotherapy or as initial management of variceal bleeding. The impact of TIPS on subsequent orthotopic liver transplantation (OLT) is uncertain. The purpose of this study was to analyze the effect of TIPS on OLT in terms of operative transfusion requirements, operative time, length of hospital stay, and graft and patient survival. The results in 17 patients undergoing TIPS for control of initial or recurrent variceal bleeding prior to OLT between June 1991 and December 1992 were compared to two other groups undergoing transplantation: 32 control patients with a history of variceal bleeding not treated by TIPS and 11 patients with a previous surgical portosystemic shunt. Compared with control and surgical shunt patients, patients who underwent TIPS had less transfusion requirement for packed red blood cells and fresh frozen plasma during OLT. The operative time and hospital stay of the TIPS patients were slightly, but not significantly, less. In contrast to patients having TIPS, the patients with a history of a previous surgical shunt had an increased requirement for packed red blood cells, longer operative time, and longer stay in the intensive care unit and hospital. Two patients had recurrent variceal bleeding after TIPS; one patient was found to have an occluded stent, and the other patient (with a patent stent) responded to sclerotherapy. Of the 14 patients with ascites, 8 patients improved and 6 patients had complete resolution after TIPS. There were no major complications related to TIPS, although 3 patients had new or recurrent hepatic encephalopathy that was easily manageable.(ABSTRACT TRUNCATED AT 250 WORDS)

The CD39 lymphoid cell activation antigen. Molecular cloning and structural characterization

CD39, a 70- to 100-kDa molecule expressed primarily on activated lymphoid cells, was previously shown to mediate B cell homotypic adhesion when ligated with a subset of anti-CD39 mAbs. In the present study, we describe the cloning and molecular characterization of human and murine CD39. The nucleotide sequence of human CD39 includes an open reading frame encoding a putative 510 amino acid protein with six potential N-linked glycosylation sites, 11 Cys residues, and two potential transmembrane regions. Murine CD39 shares 75% amino acid sequence identity with human CD39 but fails to cross-react with anti-human CD39 mAbs. Although there were no significant similarities with other mammalian genes, considerable homology was found between CD39 and a guanosine diphosphatase from yeast. A series of mouse-human hybrid molecules was constructed to determine the general topology of CD39 and the location of a biologically functional epitope. These findings and supporting evidence from an anti-CD39 mAb-selected phage peptide display library indicate a likely model wherein a short intracellular N-terminus is followed by a large extracellular loop containing the epitope recognized by stimulatory anti-CD39 mAbs, and a short intracellular C terminus. The results demonstrate that CD39 is a novel cell surface glycoprotein with unusual structural characteristics.

The CD39 lymphoid cell activation antigen. Molecular cloning and structural characterization

CD39, a 70- to 100-kDa molecule expressed primarily on activated lymphoid cells, was previously shown to mediate B cell homotypic adhesion when ligated with a subset of anti-CD39 mAbs. In the present study, we describe the cloning and molecular characterization of human and murine CD39. The nucleotide sequence of human CD39 includes an open reading frame encoding a putative 510 amino acid protein with six potential N-linked glycosylation sites, 11 Cys residues, and two potential transmembrane regions. Murine CD39 shares 75% amino acid sequence identity with human CD39 but fails to cross-react with anti-human CD39 mAbs. Although there were no significant similarities with other mammalian genes, considerable homology was found between CD39 and a guanosine diphosphatase from yeast. A series of mouse-human hybrid molecules was constructed to determine the general topology of CD39 and the location of a biologically functional epitope. These findings and supporting evidence from an anti-CD39 mAb-selected phage peptide display library indicate a likely model wherein a short intracellular N-terminus is followed by a large extracellular loop containing the epitope recognized by stimulatory anti-CD39 mAbs, and a short intracellular C terminus. The results demonstrate that CD39 is a novel cell surface glycoprotein with unusual structural characteristics.

Comparison of transjugular and surgical portosystemic shunts on the outcome of liver transplantation

OBJECTIVE

To analyze the effect of previous transjugular intrahepatic portosystemic shunt (TIPS) vs surgical portosystemic shunt (SPS) on the outcome of orthotopic liver transplantation (OLT).

DESIGN

A case series of 38 patients who underwent OLT: 25 with a previous TIPS and 13 with a previous SPS.

SETTING

A liver transplant center and interventional radiology service in a private, tertiary referral medical center.

PATIENTS

Eighteen men and seven women who had a TIPS before OLT were compared with nine men and four women who had an SPS before OLT.

MAIN OUTCOME MEASURES

Operative transfusion requirements, operative time, length of hospital stay, postoperative liver chemistry studies, and graft and patient survival.

RESULTS

Compared with patients who had an SPS, patients who had a TIPS had significantly less median transfusion requirements for packed red blood cells (5 vs 12 U), fresh-frozen plasma (0 vs 8 U), and thrombocytes (0 vs 1 U). The median operative time (9 vs 13 hours), length of intensive care unit stay (3 vs 5 days), and length of hospital stay (12 vs 24 days) were also significantly less in patients who had a TIPS. The 2-year actuarial patient survival rate was 92% in both groups.

CONCLUSIONS

In patients undergoing OLT, TIPS is associated with reduced operative transfusion requirements, operative time, and length of intensive care unit and hospital stays compared with SPS. In the potential liver transplant candidate with refractory complications of portal hypertension, TIPS is preferred to SPS.

Two saturable mechanisms of iron uptake from transferrin in human melanoma cells: the effect of transferrin concentration, chelators, and metabolic probes on transferrin and iron uptake

The mechanisms of iron (Fe) and transferrin (Tf) uptake by the human melanoma cell line, SK-MEL-28, have been investigated using chelators and metabolic probes. These data provide evidence for two saturable processes of Fe uptake from Tf, namely, specific receptor-mediated endocytosis and a second nonspecific, non-receptor-mediated mechanisms which saturated with respect to Fe uptake at a Tf concentration of approximately 0.3 mg/ml. In contrast to Fe uptake, Tf uptake increased linearly up to at least 1 mg/ml. Furthermore, under the culture conditions used, the second nonspecific, non-receptor-mediated mechanism was the most important process in terms of quantitative Fe uptake. Two concentrations of Tf-125I-59Fe (0.01 and 0.1 mg/ml) were used in order to characterise the specific and nonspecific Fe uptake pathways. Membrane permeable chelators were equally effective at both Tf concentrations, whereas membrane impermeable chelators were significantly (P < 0.001) more effective at reducing the internalisation of Fe at the higher Tf concentration, consistent with a mechanism of Fe uptake which occurred at a site in contact with the extracellular medium. The oxidoreductase inhibitor, amiloride, only slightly inhibited Fe uptake at the higher Tf concentration, suggesting that the second nonspecific process was not mediated by a diferric Tf reductase. Three lysosomotrophic agents and the endocytosis inhibitor, phenylglyoxal, markedly reduced Fe uptake at both Tf concentrations, and it is concluded that a saturable process consistent with receptor-mediated endocytosis of Tf occurred at the lower Tf concentration, while the predominant mechanism of Fe uptake at high Tf concentrations was a second saturable process consistent with adsorptive pinocytosis.

Longitudinal monitoring of intracranial arterial stenoses with transcranial Doppler ultrasonography

The natural history of intracranial arterial stenoses remains relatively unknown. To monitor the progression of these lesions over time, the authors reviewed transcranial Doppler (TCD) laboratory reports at five hospitals for patients with angiographically documented intracranial arterial stenoses along the internal carotid artery distribution, and at least two TCD studies conducted more than 2 months apart. Twenty-two patients (19 men and 3 women; mean age, 64 years) with 29 stenoses were identified. The findings were compared to reproducibility data obtained from 11 age-matched control subjects with repeat TCD studies. During a mean follow-up period of 21 months, peak systolic flow velocities corresponding to the areas of stenosis increased in 9 arteries with lesions, and new collateral flow patterns, indicating further hemodynamic compromise distal to the lesions, developed in 2; one of the latter also had increased corresponding velocities. Thus, 10 (35%) arteries with lesions had TCD evidence of progression. Flow velocities remained the same in 13 (45%) stenotic vessels and dropped in 2 (7%). Findings were considered inconclusive for 4 lesions (14%). These findings suggest that intracranial arterial stenoses are dynamic lesions, and that they can evolve and cause further reductions of the arterial diameters after relatively short periods of time. TCD can noninvasively detect their hemodynamic effects.

Molecular characterization of murine and human OX40/OX40 ligand systems: identification of a human OX40 ligand as the HTLV-1-regulated protein gp34

A ligand was cloned for murine OX40, a member of the TNF receptor family, using a T cell lymphoma cDNA library. The ligand (muOX40L) is a type II membrane protein with significant identity to human gp34 (gp34), a protein whose expression on HTLV-1-infected human leukemic T cells is regulated by the tax gene. The predicted structures of muOX40L and gp34 are similar to, but more compact than, those of other ligands of the TNF family. Mapping of the muOX40L gene revealed tight linkage to gld, the FasL gene, on chromosome 1. gp34 maps to a homologous region in the human genome, 1q25. cDNAs for human OX40 receptor were cloned by cross-hybridization with muOX40, and gp34 was found to bind the expressed human receptor. Lymphoid expression of muOX40L was detected on activated T cells, with higher levels found on CD4+ rather than CD8+ cells. The cell-bound recombinant ligands are biologically active, co-stimulating T cell proliferation and cytokine production. Strong induction of IL-4 secretion by muOX40L suggests that this ligand may play a role in regulating immune responses. In addition, the HTLV-1 regulation of gp34 suggests a possible connection between virally induced pathogenesis and the OX40 system.

Genomic organization, exact localization, and tissue expression of the human CD26 (dipeptidyl peptidase IV) gene

CD26 is a lymphocyte cell surface antigen which is increased during T-cell activation and is also expressed in other tissues. It is an atypical serine protease belonging to the prolyl oligopeptidase family. CD26 has been implicated in a variety of biological functions including T-cell activation, cell-to-cell adhesion, and recently in HIV infection. This paper describes, through the isolation and partial sequencing of eight human CD26 genomic clones, the first information on the genomic organization of the prolyl oligopeptidase family. We have established that the human CD26 gene spans approximately 70 kilobases (kb) and contains 26 exons, ranging in size from 45 base pairs (bp) to 1.4 kb. The nucleotides that encode the serine recognition site (G-W-S-Y-G) are split between two exons. This clearly distinguishes the genomic organization of the prolyl oligopeptidase family from that of the classical serine protease family. The 5' flanking domain of the CD26 gene contains neither a TATA box nor a CAAT box, but a 300 bp region extremely rich in C and G (72%) contains potential binding sites for several transcriptional factors. The human CD26 gene encodes two messages sized at about 4.2 and 2.8 kb. These are both expressed at high levels in the placenta and kidney and at moderate levels in the lung and liver. Only the 4.2 kb mRNA was expressed at low levels in skeletal muscle, heart, brain, and pancreas. Fluorescence in situ hybridization on metaphase chromosome spreads located the human CD26 gene to the long arm of chromosome 2(2q24.3).

Molecular and biological characterization of human 4-1BB and its ligand

4-1BB was originally described as a cDNA expressed by activated murine T cells and subsequently demonstrated to encode a member of the tumor necrosis factor receptor family of integral membrane proteins. Recently, we identified and cloned a murine ligand for 4-1BB (mu4-1BB-L) and demonstrated it to be a member of an emerging family of ligands with structural homology to tumor necrosis factor. To characterize further the role of 4-1BB in the immune response we undertook to clone the human homologue of 4-1BB-L. However, attempts to isolate a cDNA encoding the human 4-1BB-L by cross-hybridization with the murine cDNA were unsuccessful. Therefore we first utilized cross-species hybridization to isolate a cDNA encoding human 4-1BB (hu4-1BB). A fusion protein consisting of the extracellular portion of hu4-1BB coupled to the Fc region of human immunoglobulin G1 (hu4-1BB.Fc) was then used to identify and clone a gene for human 4-1BB-L from an activated CD4+ T cell clone using a direct expression cloning strategy. Human 4-1BB-L shows 36% amino acid identity with its murine counterpart and maps to chromosome 19p13.3. Scatchard analysis demonstrated high-affinity binding of hu4-1BB.Fc to either native or recombinant human 4-1BB-L. Both monoclonal antibody to hu4-1BB and cells transfected with hu4-1BB-L induced a strong proliferative response in mitogen co-stimulated primary T cells. In contrast, ligation of 4-1BB on T cell clones enhanced activation-induced cell death when triggered by engagement of the TCR/CD3 complex.

Cloning, chromosomal mapping and characterization of the human metal-regulatory transcription factor MTF-1

Metallothioneins (MTs) are small cysteine-rich proteins that bind heavy metal ions such as zinc, cadmium and copper with high affinity, and have been functionally implicated in heavy metal detoxification and radical scavenging. Transcription of metallothioneins genes is induced by exposure of cells to heavy metals. This induction is mediated by metal-responsive promoter elements (MREs). We have previously cloned the cDNA of an MRE-binding transcription factor (MTF-1) from the mouse. Here we present the human cDNA equivalent of this metal-regulatory factor. Human MTF-1 is a protein of 753 amino acids with 93% amino acid sequence identity to mouse MTF-1 and has an extension of 78 amino acids at the C-terminus without counterpart in the mouse. The factors of both species have the same overall structure including six zinc fingers in the DNA binding domain. We have physically mapped the human MTF-1 gene to human chromosome 1 where it localizes to the short arm in the region 1p32-34, most likely 1p33. Both human and mouse MTF-1 when produced in transfected mammalian cells strongly bind to a consensus MRE of metallothionein promoters. However, human MTF-1 is more effective than the mouse MTF-1 clone in mediating zinc-induced transcription.

Characterization of CGRP receptors in various regions of gerbil brain

The distribution of specific calcitonin gene-related peptide (CGRP) binding sites was investigated in gerbil brain regions such as cortex, cerebellum, hypothalamus, and hippocampus. The binding of [125I]CGRP to membranes prepared from these regions of the gerbil brain was rapid, saturable and specific with dissociation constants (Kd) between 10-40 pM and maximum binding (Bmax) between 10-30 fmol/mg protein. Human and rat CGRP and hCGRP8-37 competed for [125I]hCGRP binding in a concentration-dependent manner with a Ki of 10-100 pM. Salmon calcitonin was very weak in competing for [125I]hCGRP binding (ki > 10 microM). CGRP did not stimulate adenylate cyclase in these brain regions. Cross-linking of [125I] hCGRP to the brain membrane fractions with disuccinimidyl suberate revealed specific incorporation of [125I] hCGRP to a protein band of approximate molecular weight 52 kDa.

Characterization of a functional angiotensin II receptor in Xenopus laevis heart

High-affinity (104 +/- 18 pmol/l) and high-density (204 +/- 25 fmol/mg) angiotensin II (AII) binding sites have been identified in Xenopus laevis heart membranes. Competition binding of [125I]Sar1,Ile8 angiotensin (SIA) to these receptors by peptide analogs selective for the mammalian AII receptor subtypes AT1 and AT2 suggested that the amphibian AII binding sites were more closely related to the AT1 receptor subtype. Also in common with AT1 receptors, dithiothreitol and GTP gamma S inhibited [125I]SIA binding to Xenopus heart receptors, exhibiting IC50 values of 600 and 0.95 mumol/l, respectively. In addition, Xenopus oocytes injected with Xenopus heart mRNA were capable of mobilizing calcium when exposed to AII, demonstrating that Xenopus AII receptors are functionally linked to a second-messenger system similar to that coupled to mammalian AT1 receptors. However, in contrast to both AT1 and AT2 receptor subtypes, nonpeptide antagonists DUP 753 and SK&F 108566 (AT1 receptor selective) and PD123319 (AT2 selective) did not bind the Xenopus AII receptors, thus establishing that the amphibian receptors were pharmacologically unique. Together, these results demonstrate that Xenopus heart AII receptors are functionally similar to mammalian AT1 receptors but are pharmacologically distinct from both AT1 and AT2 receptors.

Human AT1 receptor is a single copy gene: characterization in a stable cell line

To address conflicting reports concerning the number of angiotensin II (AII) receptor type 1 (AT1) coding loci in vertebrates, Southern blot analysis was used to determine the genomic representation of AT1 receptor genes in animals comprising a divergent evolutionary spectrum. The data demonstrate that the AT1 receptor gene is present as a single genomic copy in a broad spectrum of animals including human, monkey, dog, cow, rabbit, and chicken. In contrast, members of the rodent taxonomic order contain two genes in their genomes. These two genes may have arisen in rodents as a consequence of a gene duplication event that occurred during evolution following the branching of rodents from the mammalian phylogenetic tree. In order to investigate the properties of the human AT1 receptor in a pure cell system, the recombinant human AT1 receptor was stably expressed in mouse L cells. An isolated cell line, designated LhAT1-D6, was found to express abundant levels of recombinant receptor [430 +/- 15 fmol/mg] exhibiting high affinity [KD = 0.15 +/- 0.02 nM] for [125I][SAR1, Ile8] angiotensin II (SIA). The pharmacological profile of ligands competing for [125I] SIA binding to the expressed receptor was in accordance with that of the natural receptor. Radioligand binding of the expressed receptor was decreased in the presence of the non-hydrolyzable analog of GTP, guanosine 5'-(gamma-thio) triphosphate [GTP gamma S]. Angiotensin II evoked a rapid efflux of 45Ca2+ from LhAT1-D6 cells that was blocked by AT1 receptor specific antagonists. In addition, AII inhibited forskolin-stimulated cAMP accumulation in these cells which was blocked by the AT-1 antagonist. Thus, the LhAT1-D6 cell line provides a powerful tool to explore the human AT1 receptor regulation.

The mouse CD69 gene. Structure, expression, and mapping to the NK gene complex

CD69 is a rapidly induced T cell activation Ag that is also expressed in an inducible fashion on cells of most, if not all, hematopoietic lineages. Molecular cloning has shown that CD69 is a type II membrane glycoprotein that is a member of the C-type lectin family. In this report we have shown that induction of CD69 mRNA in activated murine thymocytes and T cells is very rapid, peaking between 30 and 60 min poststimulation, and transient, dropping to nearly resting levels by 8 h. An analysis of the mouse CD69 gene structure showed the gene to consist of 5 exons and have a phorbol ester-inducible promoter element within the first 700 bp upstream of the start of transcription. Chromosomal mapping placed the mouse CD69 gene on the long arm of chromosome 6 near the NK gene complex that contains the related NKR-P1 and Ly-49 gene families. The human CD69 gene mapped to chromosome 12p13 near the related NKG2 gene cluster and in a region associated with rearrangements in approximately 10% of cases of childhood acute lymphocytic leukemia.

The effect of the iron(III) chelator, desferrioxamine, on iron and transferrin uptake by the human malignant melanoma cell

The mechanism of action of the clinically used iron(III) chelator, desferrioxamine (DFO), on preventing iron (Fe) uptake from transferrin (Tf) has been investigated using the human melanoma cell line SK-MEL-28. This investigation was initiated due to the paucity of information on the mechanisms of action of DFO in neoplastic cells and because recent studies have suggested that DFO may be a useful antitumor agent. The effect of DFO was dependent on incubation time. After a 2-h incubation, DFO acted like the extracellular chelators, EDTA and diethylenetriaminepentaacetic acid, because there was little inhibition of 59Fe uptake from Tf. In contrast, after a 24-h incubation, DFO (0.5 mM) efficiently reduced internalized 59Fe uptake from Tf to 18% of the control value. These observations suggested the existence of a kinetic block to the entry of the apochelator to intracellular Fe pools and/or to the exit of the DFO-59Fe complex. Indeed, cellular fractionation demonstrated that, in contrast to the decrease in the percentage of 59Fe in the ferritin and membrane fractions, a marked increase in the percentage of 59Fe present in the ferritin-free cytosol occurred. These observations suggested an accumulation of the DFO-59Fe complex within the cell. The highly lipophilic Fe chelator, pyridoxal isonicotinoyl hydrazone, was far more effective than DFO at preventing 59Fe uptake from Tf, illustrating the importance of membrane permeability for effective Fe chelation. Desferrioxamine at a concentration of 1 mM decreased internalized 125I-Tf uptake to 70% of the control. However, the decrease in 59Fe uptake observed could only be partially accounted for by a decrease in Tf uptake, and it appeared that DFO was chelating 59Fe at an intracellular site consistent with the transit Fe pool. The results are discussed in the context of the use of Fe chelators as effective antineoplastic agents.

Phorbol ester-induced transcription of an immediate-early response gene by human T cells is inhibited by co-treatment with calcium ionophore

Human T cells require two discrete signals to initiate their proliferation. In Jurkat T cells the first signal can be provided by the phorbol ester TPA and the second by the calcium ionophore A23187. We have isolated a cDNA from Jurkat T cells representing mRNA induced by TPA but inhibited by simultaneous treatment of the cells with antibody, lectin, or A23187. Sequencing revealed identity of the Jurkat clone to a cDNA, termed ETR101, recently isolated from HL60 promyelocytic leukaemia cells and shown to be an immediate early gene expressed upon TPA stimulation of these cells [Shimizu et al.: J Biol Chem 266:12157, 1991]. The gene is also induced very rapidly upon TPA treatment of Jurkat cells and is superinduced by co-treatment with cycloheximide. The predicted amino acid sequence encoded by ETR101 has weak homology to JunB and JunD, therefore it is of some interest that these three genes share the chromosomal localization, 19p13.2. The divergent effects of TPA treatment upon cell proliferation and differentiation in different circumstances allow some speculation about a possible role for the ETR101 gene product upon cellular differentiation.

The mouse CD69 gene. Structure, expression, and mapping to the NK gene complex

CD69 is a rapidly induced T cell activation Ag that is also expressed in an inducible fashion on cells of most, if not all, hematopoietic lineages. Molecular cloning has shown that CD69 is a type II membrane glycoprotein that is a member of the C-type lectin family. In this report we have shown that induction of CD69 mRNA in activated murine thymocytes and T cells is very rapid, peaking between 30 and 60 min poststimulation, and transient, dropping to nearly resting levels by 8 h. An analysis of the mouse CD69 gene structure showed the gene to consist of 5 exons and have a phorbol ester-inducible promoter element within the first 700 bp upstream of the start of transcription. Chromosomal mapping placed the mouse CD69 gene on the long arm of chromosome 6 near the NK gene complex that contains the related NKR-P1 and Ly-49 gene families. The human CD69 gene mapped to chromosome 12p13 near the related NKG2 gene cluster and in a region associated with rearrangements in approximately 10% of cases of childhood acute lymphocytic leukemia.