Nonsense mutation of glucokinase gene in late-onset non-insulin-dependent diabetes mellitus

A nonsense mutation at codon 186 in exon 5 of the gene for glucokinase, an enzyme important for glucose-induced insulin secretion, was identified in a Japanese patient with late-onset non-insulin-dependent diabetes mellitus (NIDDM). All affected members of her family were heterozygous for the mutation and had late-onset NIDDM or impaired glucose tolerance, whereas unaffected members showed normal glucose tolerance. The early insulin response to oral glucose was impaired in affected relatives, but was normal in those unaffected. These findings suggest that the glucokinase mutation raises the set-point of pancreatic beta cells for glucose-induced insulin secretion, leading to abnormal glucose tolerance in some patients with late-onset NIDDM.

Evidence for an essential histidine residue in 4S-limonene synthase and other terpene cyclases

(4S)-Limonene synthase, isolated from glandular trichome secretory cell preparations of Mentha x piperita (peppermint) leaves, catalyzes the metal ion-dependent cyclization of geranyl pyrophosphate, via 3S-linalyl pyrophosphate, to (-)-(4S)-limonene as the principal product. Treatment of this terpene cyclase with the histidine-directed reagent diethyl pyrocarbonate at a concentration of 0.25 mM resulted in 50% loss of enzyme activity, and this activity could be completely restored by treatment of the preparation with 5 mM hydroxylamine. Inhibition with diethyl pyrocarbonate was distinguished from inhibition with thiol-directed reagents by protection studies with histidine and cysteine carried out at varying pH. Inactivation of the cyclase by dye-sensitized photooxidation in the presence of rose bengal gave further indication of the presence of a readily modified histidine residue. Protection of the enzyme against inhibition with diethyl pyrocarbonate was afforded by the substrate geranyl pyrophosphate in the presence of Mn2+, and by the sulfonium ion analog of the linalyl carbocation intermediate of the reaction in the presence of inorganic pyrophosphate plus Mn2+, suggesting that an essential histidine residue is located at or near the active site. Similar studies on the inhibition of other monoterpene and sesquiterpene cyclases with diethyl pyrocarbonate suggest that a histidine residue (or residues) may play an important role in catalysis by this class of enzymes.

Islet amyloid polypeptide/amylin in pancreatic beta-cell line derived from transgenic mouse insulinoma

We examined the production and secretion of IAPP in a beta-cell line, MIN6, which is derived from an insulinoma obtained by targeted expression of the SV40 T-antigen gene in a transgenic mouse. RNA blot analysis revealed an abundance of IAPP and insulin II mRNA in the cells, findings comparable with those in the pancreas of a normal mouse. The presence of IAPP and insulin was confirmed immunohistochemically and by RIA. Analysis of the reverse-phase HPLC identified IAPP in cells with authentic mouse IAPP. Raising the glucose concentration from 5.6 to 25 mM failed to induce increments in IAPP and insulin II mRNAs. The cells secrete IAPP and insulin for short- and long-term incubations in response to concentration of glucose in the medium. These features resemble those of islet cells from normal animals. This beta-cell line will aid in analyzing the regulation of IAPP gene expression and the mechanisms of IAPP biosynthesis and secretion.

Prevention of autoimmune insulitis in nonobese diabetic mice by expression of major histocompatibility complex class I Ld molecules

Nonobese diabetic (NOD) mice spontaneously develop a T-cell-mediated autoimmune disease that is similar in many respects to insulin-dependent diabetes mellitus in humans. NOD mice were shown to express major histocompatibility complex class I Kd and Db antigens. To examine the possible involvement of major histocompatibility complex class I molecules in the development of autoimmune insulitis, we attempted to express a different type of class I molecule in NOD mice by crossing C57BL/6 mice transgenic for the class I Ld gene with NOD mice. The backcross progeny expressed the Ld antigen on the peripheral blood lymphocytes at a level comparable with that of the BALB/c mice. The cell surface expression of endogenous class I and class II antigens on the peripheral blood lymphocytes was not affected. Analysis of these mice revealed that the expression of the class I Ld antigen significantly reduced the incidence of insulitis at 20 weeks of age. In situ hybridization of a biotinylated probe on mouse chromosomes showed that the Ld transgene was located in the E area of chromosome 6 with which no genetic linkage to insulin-dependent diabetes mellitus was demonstrated. These results suggest that the NOD-type class I molecules are involved in the development of insulitis in NOD mice.

Histological distribution and developmental changes of tropomyosin isoforms in three chicken digestive organs

Histological localization of tropomyosin isoforms in three digestive organs from embryonic and adult chickens was performed by using rabbit antisera against chicken skeletal muscle tropomyosin and against low-Mr-type tropomyosin from chicken small intestine mucosa. The former antiserum (named TM-SH) reacted with alpha, beta, and high-Mr-type isoforms, and the latter (named TM-HL) reacted with alpha, beta, high-Mr-type and low-Mr-type isoforms, alpha and beta Isoforms were detected in muscle cells of the muscular layer and the muscularis mucosa. Low-Mr-type isoforms, however, were detected along the cell membrane and cytoplasm of almost all nonmuscle cells, especially in terminal webs of epithelial cells. Developmental changes of tropomyosin isoforms in digestive organs were studied by two-dimensional gel electrophoresis and image analysis. The relative amounts of alpha and beta isoforms increased in the course of development, but those of low-Mr-type and high-Mr-type isoforms decreased.

[Granulocyte functions of chronic hemodialysis patients]

With increasing number of chronic hemodialysis (HD) patients, urologists share much more chance to encounter HD patients who need urological operations. In these patients healing of surgical wound was sometimes hampered by intractable infection. In this paper we investigated granulocyte functions of HD patients. Thirty two male HD patients (20-50 years of age) and 18 healthy volunteers, who had no infectious foci and had no anti-inflammatory drugs were adopted. Heparinized blood samples were drawn between 8:00 an 9:00 am from the volunteers, and just before HD from the HD patients. The oxygen dependent microbicidal response of granulocytes was evaluated by luminol dependent chemiluminescence which measured the amount of superoxide produced by opsonized zymosan stimulated granulocytes. Phagocytic function of granulocytes was evaluated by counting the number of granulocytes which phagocytized fluorescent monodisperse carboxylated microspheres by flow cytometry. Superoxide production per 1000 granulocytes of HD patients was significantly higher than that of normal control. During HD superoxide production was temporally decreased for the first one hour, became maximal at the end of HD and returned to the baseline level on the second post HD day. Phagocytosis was significantly depressed in HD patients. This functional deficit could lead to prolonged healing of infection in HD patients.

[Transgenic mouse and gene targeting]

Transgenic mouse technology has proved to be a powerful tool for medical research. So far, a large number of transgenic mice have been generated expressing, e.g. oncogenes, viral genes, immunoglobulins, lymphokines and MHC antigens, and have provided much valuable information. Furthermore, gene targeting technology (homologous recombination between specific chromosomal DNA sequences and exogenously introduced DNA sequences) has been improved and applied to pluripotent, mouse embryonic stem (ES) cells, providing the means to create mice of specifically altered genotype. In this review, some of the background and recent advances of transgenic mouse technology and gene targeting in mouse ES cells are described.

A murine thymic stromal cell line which may support the differentiation of CD4-8- thymocytes into CD4+8- alpha beta T cell receptor positive T cells

A fibroblastoid cell line TSt-4 was established from fetal thymus tissue of C57BL/6 mice. When fetal thymus (FT) cells or CD4-8- (DN) cells of adult thymuses were cultured on the monolayer of TSt-4, a considerable proportion of lymphocytes expressed CD4 or both CD4 and CD8 within 1 day, and the CD4+CD8- cells were maintained further while the CD4+8+ cells disappeared by Day 5. A large proportion of cells generated from DN cells but not FT cells was shown to express CD3 and T cell receptor alpha beta. Addition of recombinant interleukin (IL)-7 into the cultures resulted in a marked increase of cell recovery without virtual change in differentiation process of alpha beta lineage. The present work strongly suggests that thymic fibroblasts play an important role in T cell differentiation and IL-7 contributes to supporting proliferation of differentiated cells.

Accumulation of crystallin in developing chicken lens

Separation and quantitation of crystallin subunits in embryonic and post-hatched chicken lens were carried out by two-dimensional gel electrophoresis and an image analysing system in order to elucidate detail in the accumulation process of each crystallin subunit in lens differentiation. Complete separation of the subunits was possible when 7 M urea was included in the second dimension gel of the electrophoresis. In particular, beta-crystallin could be separated into more than 24 spots on the gel. These experiments showed that delta-crystallin accumulated rapidly during early development up to more than 80% of total crystallins, while beta-crystallin accumulated quickly only after hatching. In contrast with the contents of beta- and delta-crystallins, alpha-crystallin content in total crystallins was kept at approximately 18% throughout lens development. Therefore, it was concluded that crystallins accumulated in several different ways. This suggests that different regulation mechanisms work on the accumulation of each crystallin subunit and that the subunit composition of lens proteins is specific to each state of lens development.

Mutational analysis of the structure and function of the xeroderma pigmentosum group A complementing protein. Identification of essential domains for nuclear localization and DNA excision repair

We showed previously that the xeroderma pigmentosum group A complementing (XPAC) protein involved in the DNA excision repair pathway contains a zinc-finger motif and is localized in the nucleus of normal human cells. For detailed structural and functional analyses of the XPAC protein, we constructed various XPAC cDNAs by site-directed mutagenesis and isolated permanent cell lines expressing mutant proteins. Immunofluorescent analysis of these lines indicated that the nuclear localization signal is located in the region encoded by Exon 1, especially centered at amino acids 30-42. A UV survival study showed that regions from Exons 2 through 6 were essential for DNA repair function, but that Exon 1 was not. Interestingly, deletion of the glutamic acid cluster in the region encoded by Exon 2 resulted in a dramatic loss of DNA repair activity. Furthermore, replacements of each of the 4 cysteines supposed to form a zinc-finger structure in the region encoded by Exon 3 by serine or glycine resulted in similar levels of loss of repair activity. These results suggest that all 4 cysteines forming a zinc-finger structure and also the glutamic acid cluster are important for DNA repair function.

Developmental and liver-specific expression directed by the serum amyloid P component promoter in transgenic mice

Transgenic mice were produced by microinjection of a human serum amyloid P component (hSAP) gene or a fusion gene (SS) comprising the promoter for hSAP (nucleotides -600 to -14 from the start codon) and the coding region of the hepatitis B virus surface antigen (HBsAg). In adult mice, both transgenes were expressed only in the liver, and thus the pattern of expression resembled that of the endogenous mouse SAP gene. Both hSAP mRNA and HBsAg were first detected in liver on the second postnatal day. The level of these products increased rapidly and reached the maximum within the first week. These results suggest that the hSAP gene contains a short, cis-acting, developmental, and liver-specific regulatory sequence at the 5' or the 3' end and that this sequence can target expression of the foreign gene.

Transgenic mouse as a tool for the study of autoimmune disease: insulin-dependent diabetes mellitus

Transgenic mice have been used for analyses of cis-acting elements which are involved in the tissue-specific and developmental-specific expression, for analyses of physiological function of genes, or for the production of a human disease model. This approach is especially successful in the fields of immunology and oncology. Several years ago it was shown that the major histocompatibility complex (MHC) class II gene is identical to the immune response gene by demonstrating that the immune response can be restored by the new expression of class II molecules on immunocompetent cells. Recent evidence suggests that the class II molecule is involved in the generation of autoimmune disease, such as insulin-dependent diabetes mellitus (IDDM). The NOD (non-obese diabetic) mouse is shown to be a mouse model for human IDDM. Concerning the class II genes, the NOD mouse has two characteristic features, the lack of I-E and the presence of unique I-A. It is discussed how the role of class II molecules in the development of IDDM in the NOD mouse can be analyzed. In addition, the transgenic technique can be applied to the study of differentiation and oncogenesis of lymphoid cells. Factors or molecules that affect these processes will also be discussed.

Characterization of T-cell tolerance to hepatitis B virus (HBV) antigen in transgenic mice

We made three different lines of hepatitis B virus (HBV) transgenic mice which express different amounts of hepatitis B e antigen (HBeAg) and/or hepatitis B core antigen (HBcAg) to analyse the cellular mechanisms of HBcAg specific T-cell tolerance. BS10 (official designation, 1.2HB-BS10) transgenic mice, which contain the whole HBV genome, express relatively high amounts of HBeAg in the serum and HBcAg in the liver. SPC mice, which contain hepatitis B virus core and precore gene, express small amounts of HBeAg in the serum but not HBcAg in the liver. SC33 mice, which contain only hepatitis B core gene, do not express HBeAg in the serum but express HBcAg in the liver. BS10 mice showed a very low anti-HBc antibody response after primary and secondary immunizations with recombinant HBcAg compared to transgenic host C57BL/6 (B6) mice. SPC mice showed an almost equal level of anti-HBc antibody response compared to B6 mice. SC33 mice contained anti-HBc antibody even before immunization and showed high titres of anti-HBc antibody response after immunization with HBcAg. Analysis of cellular site(s) of low responsiveness of BS10 mice revealed that proliferating and helper T cells are specifically tolerant to HBcAg. B cells and antigen-presenting cells in BS10 mice were not defective. SC33, SPC and BS10 mice differ a little in their developmental expression of HBc/HBeAg. Our results suggest critical roles of the nature (circulating versus non-circulating) as well as the time of expression of self-antigens in T-cell tolerance.

Strain dependency of cell-type specificity and onset of lymphoma development in Emu-myc transgenic mice

c-myc is a nuclear proto-oncogene that, when activated, induces malignancies in a variety of tissues. Most murine plasmacytomas and human Burkitt's lymphomas have been shown to carry a chromosomal translocation involving c-myc and immunoglobulin genes. To study genetic or epigenetic factors that affect myc-induced lymphoid cell tumors, we previously introduced the Emu-myc delta gene lacking its own promoter and first exon into two inbred strains of mice, C57BL/6 and C3H/HeJ. We observed three characteristic features in our transgenic mice. First, T cell lymphoma predominated in the C3H background. Second, both pre-B and B cell lymphoma developed at equal frequency in C57BL/6 transgenic mice. Third, the average age of onset is earlier than that reported by other investigators. To test whether these characteristics are due either to the lack of the promoter region and first exon of the c-myc gene in the construct or to the genetic background of the mice, we introduced Emu-myc gene containing the complete c-myc gene into fertilized eggs of C57BL/6 and C3H/HeJ mice. The cell-type specificity, differentiation-stage specificity and the average age at onset of lymphoma development were not affected by the transgene construct.

Interfacial ionization and partitioning of membrane-bound local anesthetics

Consideration of the interfacial protonation equilibria of membrane-associated amphiphiles indicates that the partition coefficients of the protonated and unprotonated species will differ considerably. The partition coefficients of the charged and uncharged forms of spin-labelled myristic acid in dimyristoylphosphatidylcholine bilayer dispersions have been measured by EPR spectroscopy and found to be approximately 140-fold higher for the protonated acid than for the dissociated salt form. This ratio of partition coefficients is found to be in good agreement with that predicted from the interfacial shift in pKa of the fatty acid on its partitioning into the membrane. The latter was determined from the changes in the EPR spectra of the membrane-associated fatty acid with pH and was found to be +2.1 pH units. The interfacial shifts in pKa for a series of spin-labelled analogues of tertiary amine local anaesthetics have been determined from the pH dependence of the partition coefficients in dimyristoylphosphatidylcholine bilayer dispersions and are found mostly to be in the range of approx. -1.0 to -1.5 pH units, corresponding to a 10- to 30-fold higher partition coefficient of the uncharged base compared with that of the charged ammonium form.

Complete prevention of diabetes in transgenic NOD mice expressing I-E molecules

Previously, we showed that transgenic expression of the MHC (major histocompatibility complex) class II I-E molecules prevented insulitis in non-obese diabetic (NOD) mice at the age of 19 weeks. To rule out the possibility that the I-E expression merely delays the onset of insulitis, we have further characterized the expression and function of the I-E molecule expressed in transgenic NOD mice and confirmed our previous observations. Northern blot analysis showed that the transgenic E alpha d gene was expressed in a pattern similar to the endogenous E alpha d gene in BALB/c mice. The newly expressed I-E molecules were recognized as an alloantigen by the T lymphocytes of normal NOD mice as shown by mixed lymphocyte reaction (MLR). Transgenic NOD mice were resistant to the treatment by cyclophosphamide, which effectively induces diabetes in normal NOD mice, and did not develop diabetes up to 40 weeks of age. On the basis of these findings, we discuss the role of I-E molecules in the prevention of diabetes in NOD mice.

Generation of plasmacytomas with the chromosomal translocation t(12;15) in interleukin 6 transgenic mice

The mechanisms through which pristane or mineral oil can induce plasmacytomas in BALB/c or NZB mice are not fully understood, but involvement of interleukin 6 (IL-6), a growth factor for plasmacytomas and myelomas, has been strongly suggested. To clarify the role of IL-6 in plasmacytomagenesis, a human IL-6 cDNA was introduced into mouse germ lines under the transcriptional control of the murine major histocompatibility complex class I (H-2Ld) promoter. IL-6 transgenic mice of C57BL/6 origin developed a massive plasmacytosis but not plasmacytomas. However, introduction of BALB/c genetic background into IL-6 transgenic mice could generate monoclonal transplantable plasmacytomas with the chromosomal translocation t(12;15). These results provide firm evidence of the critical role of IL-6 in the plasmacytoma development.

Efficient selection for high-expression transfectants with a novel eukaryotic vector

We have developed a new expression vector which allows efficient selection for transfectants that express foreign genes at high levels. The vector is composed of a ubiquitously strong promoter based on the beta-actin promoter, a 69% subregion of the bovine papilloma virus genome, and a mutant neomycin phosphotransferase II-encoding gene driven by a weak promoter, which confers only marginal resistance to G418. Thus, high concentrations of G418 (approx. 800 micrograms/ml) effectively select for transfectants containing a high vector copy number (greater than 300). We tested this system by producing human interleukin-2 (IL-2) in L cells and Chinese hamster ovary (CHO) cells, and the results showed that high concentrations of G418 efficiently yielded L cell and CHO cell transfectants stably producing IL-2 at levels comparable with those previously attained using gene amplification. The vector sequences were found to have integrated into the host chromosome, and were stably maintained in the transfectants for several months.

Development of two types of hepatocellular carcinoma in transgenic mice carrying the SV40 large T-antigen gene

We produced transgenic mice by introducing a fusion gene (ST) comprising of the promoter for human serum amyloid P component (SAP) and the coding region of the simian virus 40 (SV40) large tumor antigen (Tag). The ST transgenic mice developed hepatocellular carcinomas (HCC) between 7 and 12 weeks of age. Clinically and pathologically these HCC were classified into two types: diffuse and focal. In the diffuse type Tag is expressed in almost all hepatocytes and HCC has presumably developed from these T-antigen-positive cells. The focal type, which resembles human HCC, is only Tag positive in the neoplastic nodules. These are surrounded by Tag-negative normal hepatocytes that form normal lobular structures. As the human SAP promoter can direct adult liver-specific expression of heterologous genes, it is assumed that Tag gene expression in the transgenic animals is increased sharply after birth. Interestingly, a similar level of Tag expression was observed in both the cytoplasm and the nucleus. Our results suggest that spatial differences in Tag expression result in the generation of two types of HCC in transgenic mice and that the ST mouse can serve as a model for human hepatocarcinogenesis.

Characterization and sequence of a novel nitrate reductase from barley

Barley (Hordeum vulgare L.) has both NADH-specific and NAD(P)H-bispecific nitrate reductases. Genomic and cDNA clones of the NADH nitrate reductase have been sequenced. In this study, a genomic clone (pMJ4.1) of a second type of nitrate reductase was isolated from barley by homology to a partial-length NADH nitrate reductase cDNA and the sequence determined. The open reading frame encodes a polypeptide of 891 amino acids and its interrupted by two small introns. The deduced amino acid sequence has 70% identity to the barley NADH-specific nitrate reductase. The non-coding regions of the pMJ4.1 gene have low homology (ca. 40%) to the corresponding regions of the NADH nitrate reductase gene. Expression of the pMJ4.1 nitrate reductase gene is induced by nitrate in root tissues which corresponds to the induction of NAD(P)H nitrate reductase activity. The pMJ4.1 nitrate reductase gene is sufficiently different from all previously reported higher plant nitrate reductase genes to suggest that it encodes the barley NAD(P)H-bispecific nitrate reductase.

Identification and distribution of tropomyosin isoforms in chicken digestive canal

Two-dimensional gel electrophoresis of eight digestive organ extracts from 60-day-old chicks was performed. Judging from the similarity of their protein maps, the organs were classified into the following four types: 1) esophagus type, 2) proventriculus type, 3) gizzard type, and 4) intestine type. In four representative organs of these types, the distribution of tropomyosin isoforms was examined, and four high- and five low-Mr-type isoforms in addition to alpha and beta isoforms were detected in the embryonic organs. In the adult organs, however, there were three high- and four low-Mr-type isoforms, which were restricted to the mucous membrane, in addition to alpha and beta isoforms. Immunoblot analysis indicated that the high- and low-Mr-type isoforms in the embryo corresponded with those in the adult mucous membrane, but differences in the number and amount of the isoforms were found between the embryo and the adult mucous membrane.

(BALB/c x C57BL/6)F1 mice are tolerant to undetectable mixed haplotype A beta dA alpha b and mixed isotype A beta dE alpha d self class II molecules

The existence of mixed haplotype A beta dA alpha b and mixed isotype A beta dE alpha d molecules was demonstrated in A beta d gene introduced C57BL/6 (B6) transgenic and in A beta dE alpha d double gene introduced B6 transgenic mice, respectively. Using alloreactive and antigen reactive T-cell clones, these mixed class II molecules were shown to function as mixed lymphocyte culture reaction (MLR) stimulating determinants and restriction elements for antigen recognition by T cells. The amounts of expression of these mixed class II molecules were sufficient for the stimulation of alloreactive T cells in primary MLR culture. (BALB/c x B6)F1 (CBF1) mice were shown not to express functional mixed haplotype and mixed isotype class II molecules using alloreactive and antigen reactive T-cell clones. Interestingly, however, CBF1 mice did not respond to such mixed haplotype and mixed isotype class II molecules. These results show that CBF1 mice do not respond to undetectably-expressed class II molecule and suggest that they are tolerant to undetectable self class II molecules. The possible interpretations for this are discussed.