Essential requirement of an invariant V alpha 14 T cell antigen receptor expression in the development of natural killer T cells.

NK1.1+ T [natural killer (NK) T] cells express an invariant T cell antigen receptor alpha chain (TCR alpha) encoded by V alpha 14 and J alpha 281 segments in association with a limited number of V betas, predominantly V beta 8.2. Expression of the invariant V alpha 14/J alpha 281, but not V alpha 1, TCR in transgenic mice lacking endogenous TCR alpha expression blocks the development of conventional T alpha beta cells and leads to the preferential development of V alpha 14 NK T cells, suggesting a prerequisite role of invariant V alpha 14 TCR in NK T cell development. In V beta 8.2 but not B beta 3 transgenic mice, two NK T cells with different CD3 epsilon expressions, CD3 epsilon(dim) and CD3 epsilon(high), can be identified. CD3 epsilon(high) NK T cells express surface V alpha 14/V beta 8 TCR, indicating a mature cell type, whereas CD3 epsilon(dim) NK T cells express V beta 8 without V alpha 14 TCR and no significant CD3 epsilon expression (CD3 epsilon(dim)) on the cell surface. However, the latter are positive for recombination activating gene (RAG-1 and RAG-2) mRNA, which are only expressed in the precursor or immature T cell lineage, and also possess CD3 epsilon mRNA in their cytoplasm, suggesting that CD3 epsilon(dim) NK T cells are the precursor of V alpha 14 NK T cells.

CD38 ligation induces tyrosine phosphorylation of Bruton tyrosine kinase and enhanced expression of interleukin 5-receptor alpha chain: synergistic effects with interleukin 5.

Mouse CD38 has been implicated in the regulation of both B-cell proliferation and protection of B cells from irradiation-induced apoptosis. CD38 ligation on B cells by CS/2, an anti-mouse CD38 monoclonal antibody, induced proliferation, IgM secretion, and tyrosine phosphorylation of Bruton tyrosine kinase in B cells from wild-type mice. B cells from X chromosome-linked immunodeficient mice did not respond at all to anti-CD38 antibody, although CD38 expression on these B cells was comparable to that on wild-type B cells. We infer from these results that Bruton tyrosine kinase activation is involved in B-cell triggering after cross-linkage of CD38. Analysis of the synergistic effects of various cytokines with CD38 ligation on B-cell activation revealed that interleukin 5 (IL-5) showed the most potent effect on B-cell proliferation, Blimp1 gene expression, and IgM production. These synergistic effects were not seen with B cells from X chromosome-linked immunodeficient mice. Flow cytometry analysis revealed that CD38 ligation increased surface expression of the IL-5-receptor alpha chain on B cells. These data indicate that CD38 ligation increases IL-5 receptor alpha expression and synergizes with IL-5 to enhance Blimp1 expression and IgM synthesis.

Transcriptional activation of the mouse obese (ob) gene by CCAAT/enhancer binding protein alpha.

Like other adipocyte genes that are transcriptionally activated by CCAAT/enhancer binding protein alpha (C/EBP alpha) during preadipocyte differentiation, expression of the mouse obese (ob) gene is immediately preceded by the expression of C/EBP alpha. While the 5' flanking region of the mouse ob gene contains several consensus C/EBP binding sites, only one of these sites appears to be functional. DNase I cleavage inhibition patterns (footprinting) of the ob gene promoter revealed that recombinant C/EBP alpha, as well as a nuclear factor present in fully differentiated 3T3-L1 adipocytes, but present at a much lower level in preadipocytes, protects the same region between nucleotides -58 and -42 relative to the transcriptional start site. Electrophoretic mobility-shift analysis using nuclear extracts from adipose tissue or 3T3-L1 adipocytes and an oligonucleotide probe corresponding to a consensus C/EBP binding site at nucleotides -55 to -47 generated a specific protein-oligonucleotide complex that was supershifted by antibody against C/EBP alpha. Probes corresponding to two upstream consensus C/EBP binding sites failed to generate protein-oligonucleotide complexes. Cotransfection of a C/EBP alpha expression vector into 3T3-L1 cells with a series of 5' truncated ob gene promoter constructs activated reporter gene expression with all constructs containing the proximal C/EBP binding site (nucleotides -55 to -47). Mutation of this site blocked transactivation by C/EBP alpha. Taken together, these findings implicate C/EBP alpha as a transcriptional activator of the ob gene promoter and identify the functional C/EBP binding site in the promoter.

Identification of the promoter of the mouse obese gene.

Primer extension and RACE (rapid amplification of cDNA ends) assays were used to identify and sequence the 5' terminus of mouse ob mRNA. This sequence was used to obtain a recombinant bacteriophage containing the first exon of the encoding gene. DNA sequence analysis of the region immediately upstream of the first exon of the mouse ob gene revealed DNA sequences corresponding to presumptive cis-regulatory elements. A canonical TATA box was observed 30-34 base pairs upstream from the start site of transcription and a putative binding site for members of the C/EBP family of transcription factors was identified immediately upstream from the TATA box. Nuclear extracts prepared from primary adipocytes contained a DNA binding activity capable of avid and specific interaction with the putative C/EBP response element; antibodies to C/EBP alpha neutralized the DNA binding activity present in adipocyte nuclear extracts. When linked to a firefly luciferase reporter and transfected into primary adipocytes, the presumptive promoter of the mouse ob gene facilitated luciferase expression. When transfected into HepG2 cells, which lack C/EBP alpha, the mouse ob promoter was only weakly active. Supplementation of C/EBP alpha by cotransfection with a C/EBP alpha expression vector markedly stimulated luciferase expression. Finally, an ob promoter variant mutated at the C/EBP response element was inactive in both primary adipocytes and HepG2 cells. These observations provide evidence for identification of a functional promoter capable of directing expression of the mouse ob gene.

Inhibition of calcium/calmodulin kinase II alpha subunit expression results in epileptiform activity in cultured hippocampal neurons

Several models that develop epileptiform discharges and epilepsy have been associated with a decrease in the activity of calmodulin-dependent kinase II. However, none of these studies has demonstrated a causal relationship between a decrease in calcium/calmodulin kinase II activity and the development of seizure activity. The present study was conducted to determine the effect of directly reducing calcium/calmodulin-dependent kinase activity on the development of epileptiform discharges in hippocampal neurons in culture. Complimentary oligonucleotides specific for the α subunit of the calcium/calmodulin kinase were used to decrease the expression of the enzyme. Reduction in kinase expression was confirmed by Western analysis, immunocytochemistry, and exogenous substrate phosphorylation. Increased neuronal excitability and frank epileptiform discharges were observed after a significant reduction in calmodulin kinase II expression. The epileptiform activity was a synchronous event and was not caused by random neuronal firing. Furthermore, the magnitude of decreased kinase expression correlated with the increased neuronal excitability. The data suggest that decreased calmodulin kinase II activity may play a role in epileptogenesis and the long-term plasticity changes associated with the development of pathological seizure activity and epilepsy.

Heightened expression of tumor necrosis factor alpha, interleukin 1 alpha, and glial fibrillary acidic protein in experimental Creutzfeldt-Jakob disease in mice.

The ultrastructural pathology of myelinated axons in mice infected experimentally with the Fujisaki strain of Creutzfeldt-Jakob disease (CJD) virus is characterized by myelin sheath vacuolation that closely resembles that induced in murine spinal cord organotypic cultures by tumor necrosis factor alpha (TNF-alpha), a cytokine produced by astrocytes and macrophages. To clarify the role of TNF-alpha in experimental CJD, we investigated the expression of TNF-alpha in brain tissues from CJD virus-infected mice at weekly intervals after inoculation by reverse transcription-coupled PCR, Northern and Western blot analyses, and immunocytochemical staining. Neuropathological findings by electron microscopy, as well as expression of interleukin 1 alpha and glial fibrillary acidic protein, were concurrently monitored. As determined by reverse transcription-coupled PCR, the expression of TNF-alpha, interleukin 1 alpha, and glial fibrillary acidic protein was increased by approximately 200-fold in the brains of CJD virus-inoculated mice during the course of disease. By contrast, beta-actin expression remained unchanged. Progressively increased expression of TNF-alpha in CJD virus-infected brain tissues was verified by Northern and Western blot analyses, and astrocytes in areas with striking myelin sheath vacuolation were intensely stained with an antibody against murine TNF-alpha. The collective findings of TNF-alpha overexpression during the course of clinical disease suggest that TNF-alpha may mediate the myelin sheath vacuolation observed in experimental CJD.

Correction in trans for Fabry disease: expression, secretion and uptake of alpha-galactosidase A in patient-derived cells driven by a high-titer recombinant retroviral vector.

Fabry disease is an X-linked metabolic disorder due to a deficiency of alpha-galactosidase A (alpha-gal A; EC 3.2.1.22). Patients accumulate glycosphingolipids with terminal alpha-galactosyl residues that come from intracellular synthesis, circulating metabolites, or from the biodegradation Of senescent cells. Patients eventually succumb to renal, cardio-, or cerebrovascular disease. No specific therapy exists. One possible approach to ameliorating this disorder is to target corrective gene transfer therapy to circulating hematopoietic cells. Toward this end, an amphotropic virus-producer cell line has been developed that produces a high titer (>10(6) i.p. per ml) recombinant retrovirus constructed to transduce and correct target cells. Virus-producer cells also demonstrate expression of large amounts of both intracellular and secreted alpha-gal A. To examine the utility of this therapeutic vector, skin fibroblasts from Fabry patients were corrected for the metabolic defect by infection with this recombinant virus and secreted enzyme was observed. Furthermore, the secreted enzyme was found to be taken up by uncorrected cells in a mannose-6-phosphate receptor-dependent manner. In related experiments, immortalized B cell lines from Fabry patients, created as a hematologic delivery test system, were transduced. As with the fibroblasts, transduced patient B cell lines demonstrated both endogenous enzyme correction and a small amount of secretion together with uptake by uncorrected cells. These studies demonstrate that endogenous metabolic correction in transduced cells, combined with secretion, may provide a continuous source of corrective material in trans to unmodified patient bystander cells (metabolic cooperativity).

Reduction in the level of Gal(alpha1,3)Gal in transgenic mice and pigs by the expression of an alpha(1,2)fucosyltransferase.

Hyperacute rejection of a porcine organ by higher primates is initiated by the binding of xenoreactive natural antibodies of the recipient to blood vessels in the graft leading to complement activation. The majority of these antibodies recognize the carbohydrate structure Gal(alphal,3)Gal (gal epitope) present on cells of pigs. It is possible that the removal or lowering of the number of gal epitopes on the graft endothelium could prevent hyperacute rejection. The Gal(alpha1,3) Gal structure is formed by the enzyme Galbeta1,4GlcNAc3-alpha-D-galactosyltransferase [alpha(1,3)GT; EC 2.4.1.51], which transfers a galactose molecule to terminal N-acetyllactosamine (N-lac) present on various glycoproteins and glycolipids. The N-lac structure might be utilized as an acceptor by other glycosyltransferases such as Galbeta1,4GlcNAc 6-alpha-D-sialyltransferase [alpha(2,6)ST], Galbeta1,4GlcNAc 3-alpha-D-Sialyltransferase [alpha(2,3)ST], or Galbeta 2-alpha-L-fucosyltransferase [alpha(1,2)FT; EC 2.4.1.691, etc. In this report we describe the competition between alpha(1,2)FT and alpha(1,3)GT in cells in culture and the generation of transgenic mice and transgenic pigs that express alpha(1,2)Fr leading to synthesis of Fucalpha,2Galbeta- (H antigen) and a concomitant decrease in the level of Gal(alpha1,3)Gal. As predicted, this resulted in reduced binding of xenoreactive natural antibodies to endothelial cells of transgenic mice and protection from complement mediated lysis.

Taste receptor-like cells in the rat gut identified by expression of alpha-gustducin.

The alpha-subunit of the trimeric G-protein complex specific for taste receptor cells of the tongue, alpha-gustducin, is described here to be also expressed in the stomach and intestine. The alpha-gustducin-containing cells were identified as brush cells that are scattered throughout the surface epithelium of the gut and share structural features of taste receptor cells of the tongue. These findings provide clues to the long-sought molecular and cellular basis for chemoreception in the gut.

Efficient and specific ribozyme-mediated reduction of bovine alpha-lactalbumin expression in double transgenic mice.

Transgenic mice carrying a bovine alpha-lactalbumin (alpha-lac) specific ribozyme gene under the transcriptional control of the mouse mammary tumor virus long terminal repeat were generated and cross-bred with animals that highly express a bovine alpha-lac transgene (0.4 mg of alpha-lac/ml(-1) of milk). The ribozyme contains the hammerhead catalytic domain, flanked by 12-nt sequences complementary to the 3' untranslated region of bovine alpha-lac transcript. High-level expression of the ribozyme gene was detected by Northern blot analysis in the mammary gland of 7-8 day lactating transgenic mice, from 3 of 12 lines analyzed. Heterozygous expression of the ribozyme resulted in a reduction in the levels of the target mRNA to 78, 58, and 50% of that observed in the nonribozyme transgenic littermate controls for three independent lines. The ribozyme-mediated reduction in the levels of the bovine protein paralleled that observed for the mRNA, and was positively correlated with the level of expression of the ribozyme. In nonribozyme expressing transgenic mice, the level of bovine alpha-lac mRNA and protein was not affected. The specificity of this activity is demonstrated by the absence of a reduction in the levels of the endogenous murine alpha-lac mRNA or protein. These results demonstrate the feasibility of ribozyme-mediated down-regulation of highly-expressed transcripts in transgenic animals.

Adenylyl cyclase inhibition and altered G protein subunit expression and ADP-ribosylation patterns in tissues and cells from Gi2 alpha-/-mice.

The inhibition of alpha i2-/- mouse cardiac isoproterenol-stimulated adenylyl cyclase (AC; EC 4.6.1.1) activity by carbachol and that of alpha i2-/- adipocyte AC by phenylisopropyladenosine (PIA), prostaglandin E2, and nicotinic acid were partially, but not completely, inhibited. While the inhibition of cardiac AC was affected in all alpha i2-/- animals tested, only 50% of the alpha i2-/- animals showed an impaired inhibition of adipocyte AC, indicative of a partial penetrance of this phenotype. In agreement with previous results, the data show that Gi2 mediates hormonal inhibition of AC and that Gi3 and/or Gi1 is capable of doing the same but with a lower efficacy. Disruption of the alpha i2 gene affected about equally the actions of all the receptors studied, indicating that none of them exhibits a striking specificity for one type of Gi over another and that receptors are likely to he selective rather than specific in their interaction with functionally homologous G proteins (e.g., Gi1, Gi2, Gi3). Western analysis of G protein subunit levels in simian virus 40-transformed primary embryonic fibroblasts from alpha i2+/+ and alpha i2-/- animals showed that alpha i2 accounts for about 50% of the immunopositive G protein alpha subunits and that loss of the alpha i2 is accompanied by a parallel reduction in G beta 35 and G beta 36 subunits and by a 30-50% increase in alpha i3. This suggests that G beta-gamma levels may be regulated passively through differential rates of turnover in their free vs. trimeric states. The existence of compensatory increase(s) in alpha i subunit expression raises the possibility that the lack of effect of a missing alpha i2 on AC inhibition in adipocytes of some alpha i2-/- animals may be the reflection of a more pronounced compensatory expression of alpha i3 and/or alpha i1.

Identification of a minimal sequence of the mouse pro-alpha 1(I) collagen promoter that confers high-level osteoblast expression in transgenic mice and that binds a protein selectively present in osteoblasts.

Based on our previous transgenic mice results, which strongly suggested that separate cell-specific cis-acting elements of the mouse pro-alpha 1(I) collagen promoter control the activity of the gene in different type I collagen-producing cells, we attempted to delineate a short segment in this promoter that could direct high-level expression selectively in osteoblasts. By generating transgenic mice harboring various fragments of the promoter, we identified a 117-bp segment (-1656 to -1540) that is a minimal sequence able to confer high-level expression of a lacZ reporter gene selectively in osteoblasts when cloned upstream of the proximal 220-bp pro-alpha 1(I) promoter. This 220-bp promoter by itself was inactive in transgenic mice and unable to direct osteoblast-specific expression. The 117-bp enhancer segment contained two sequences that appeared to have different functions. The A sequence (-1656 to -1628) was required to obtain expression of the lacZ gene in osteoblasts, whereas the C sequence (-1575 to -1540) was essential to obtain consistent and high-level expression of the lacZ gene in osteoblasts. Gel shift assays showed that the A sequence bound a nuclear protein present only in osteoblastic cells. A mutation in the A segment that abolished the binding of this osteoblast-specific protein also abolished lacZ expression in osteoblasts of transgenic mice.

Molecular cloning and expression of cDNAs encoding human alpha-mannosidase II and a previously unrecognized alpha-mannosidase IIx isozyme.

Golgi alpha-mannosidase II (alpha-MII) is an enzyme involved in the processing of N-linked glycans. Using a previously isolated murine cDNA clone as a probe, we have isolated cDNA clones encompassing the human alpha-MII cDNA open reading frame and initiated isolation of human genomic clones. During the isolation of genomic clones, genes related to that encoding alpha-MII were isolated. One such gene was found to encode an isozyme, designated alpha-MIIx. A 5-kb cDNA clone encoding alpha-MIIx was then isolated from a human melanoma cDNA library. However, comparison between alpha-MIIx and alpha-MII cDNAs suggested that the cloned cDNA encodes a truncated polypeptide with 796 amino acid residues, while alpha-MII consists of 1144 amino acid residues. To reevaluate the sequence of alpha-MIIx cDNA, polymerase chain reaction (PCR) was performed with lymphocyte mRNAs. Comparison of the sequence of PCR products with the alpha-MIIx genomic sequence revealed that alternative splicing of the alpha-MIIx transcript can result in an additional transcript encoding a 1139-amino acid polypeptide. Northern analysis showed transcription of alpha-MIIx in various tissues, suggesting that the alpha-MIIx gene is a housekeeping gene. COS cells transfected with alpha-MIIx cDNA containing the full-length open reading frame showed an increase of alpha-mannosidase activity. The alpha-MIIx gene was mapped to human chromosome 15q25, whereas the alpha-MII gene was mapped to 5q21-22.

Spontaneous inflammatory demyelinating disease in transgenic mice showing central nervous system-specific expression of tumor necrosis factor alpha.

Cytokines are now recognized to play important roles in the physiology of the central nervous system (CNS) during health and disease. Tumor necrosis factor alpha (TNF-alpha) has been implicated in the pathogenesis of several human CNS disorders including multiple sclerosis, AIDS dementia, and cerebral malaria. We have generated transgenic mice that constitutively express a murine TNF-alpha transgene, under the control of its own promoter, specifically in their CNS and that spontaneously develop a chronic inflammatory demyelinating disease with 100% penetrance from around 3-8 weeks of age. High-level expression of the transgene was seen in neurons distributed throughout the brain. Disease is manifested by ataxia, seizures, and paresis and leads to early death. Histopathological analysis revealed infiltration of the meninges and CNS parenchyma by CD4+ and CD8+ T lymphocytes, widespread reactive astrocytosis and microgliosis, and focal demyelination. The direct action of TNF-alpha in the pathogenesis of this disease was confirmed by peripheral administration of a neutralizing anti-murine TNF-alpha antibody. This treatment completely prevented the development of neurological symptoms, T-cell infiltration into the CNS parenchyma, astrocytosis, and demyelination, and greatly reduced the severity of reactive microgliosis. These results demonstrate that overexpression of TNF-alpha in the CNS can cause abnormalities in nervous system structure and function. The disease induced in TNF-alpha transgenic mice shows clinical and histopathological features characteristic of inflammatory demyelinating CNS disorders in humans, and these mice represent a relevant in vivo model for their further study.

Re-expression of the alpha 2 beta 1 integrin abrogates the malignant phenotype of breast carcinoma cells.

To assess the role of altered alpha 2 beta 1 integrin expression in breast cancer, we expressed the alpha 2 beta 1 integrin de novo in a poorly differentiated mammary carcinoma that expressed no detectable alpha 2-integrin subunit. Expression of the alpha 2 beta 1 integrin resulted in a dramatic phenotypic alteration from a fibroblastoid, spindle-shaped, non-contact-inhibited, motile, and invasive cell to an epithelioid, polygonal-shaped, contact-inhibited, less motile, and less invasive cell. Although expression of the alpha 2 subunit did not alter adhesion to collagen, it profoundly altered cell spreading. Re-expression of the alpha 2 beta 1 integrin restored the ability to differentiate into gland-like structures in three-dimensional matrices and markedly reduced the in vivo tumorigenicity of the cells. These results indicate that the consequences of diminished alpha 2 beta 1-integrin expression in the development of breast cancer and, presumably, of other epithelial malignancies are increased tumorigenicity and loss of the differentiated epithelial phenotype.