Polymorphisms of DQ β genes in HLA-DR4 haplotypes from healthy and diabetic individuals

The restriction fragment length polymorphism (RFLP) of DQ was assessed in a panel of control and insulin-dependent diabetes (IDD) patients who were serologically typed as HLA-DR4 homozygotes or HLA-DR3, DR4 heterozygotes. Digestions of genomic DNA with Barn HI, Bg1 II, Pst I, Xba I, and Hind III revealed a total of 15 RFLPs in the panel of 71 HLA-DR4 chromosomes. These RFLPs were organized into six allelic groups on the basis of segregation analysis in families. Complete RFLP haplotypes for the 5 restriction enzymes could be constructed for 42 of the HLA-DR4 chromosomes. This analysis revealed 18 RFLP haplotypes of DQ associated with the DR4 chromosomes tested. Two of these haplotypes, designated DQ3.DR4.a and DQ3.DR4.b, accounted for over 50 % of the DR4 chromosomes analyzed. These two haplotypes were antithetical for the RFLPs detected by all five enzymes, indicating that they represent very distinct forms of DQ . The remaining 16 haplotypes were infrequent or unique and were closely related to either a DQ3.DR4.a or DQ3.DR4.b. Two of the RFLPs detected, a 5.8 kb Bg1 II fragment and a 10.5 kb Barn HI fragment, had increased frequencies in disease-associated chromosomes. However, none of the RFLPs we detected exhibited a statistically significant increase in IDD or control populations. In contrast, the DQ3.DR4.b DQ haplotype was significantly decreased in IDD-associated DR4 chromosomes. (P=0.04). These results suggest that the DQ3.DR4.b DQ allele may be protective for the development of IDD.     

Characterization of the lipopolysaccharide from a Rhizobium phaseoli mutant that is defective in infection thread development.

The lipopolysaccharide (LPS) from a Rhizobium phaseoli mutant, CE109, was isolated and compared with that of its wild-type parent, CE3. A previous report has shown that the mutant is defective in infection thread development, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis shows that it has an altered LPS (K. D. Noel, K. A. VandenBosch, and B. Kulpaca, J. Bacteriol. 168:1392-1462, 1986). Mild acid hydrolysis of the CE3 LPS released a polysaccharide and an oligosaccharide, PS1 and PS2, respectively. Mild acid hydrolysis of CE109 LPS released only an oligosaccharide. Chemical and immunochemical analyses showed that CE3-PS1 is the antigenic O chain of this strain and that CE109 LPS does not contain any of the major sugar components of CE3-PS1. CE109 oligosaccharide was identical in composition to CE3-PS2. The lipid A's from both strains were very similar in composition, with only minor quantitative variations. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of CE3 and CE109 LPSs showed that CE3 LPS separated into two bands, LPS I and LPS II, while CE109 had two bands which migrated to positions similar to that of LPS II. Immunoblotting with anti-CE3 antiserum showed that LPS I contains the antigenic O chain of CE3, PS1. Anti-CE109 antiserum interacted strongly with both CE109 LPS bands and CE3 LPS II and interacted weakly with CE3 LPS I. Mild-acid hydrolysis of CE3 LPS I, extracted from the polyacrylamide gel, showed that it contained both PS1 and PS2. The results in this report showed that CE109 LPS consists of only the lipid A core and is missing the antigenic O chain.     

Infertility in human males with autosomal translocations: meiotic study of a 14;22 Robertsonian translocation

Summary Pachytene analysis was undertaken in a male patient heterozygous for a 14q22q Robertsonian translocation. The relatively low rate of XY autosome association led us to examine the relationships existing between the chromosomes involved in the translocation, the rate of XY-autosome association and the degree of spermatogenic failure. Cytogenetic investigations in infertile men and the results of the meiotic studies suggest a direct correlation between the frequency of XY-autosome association at pachytene and the degree of spermatogenic failure. Whether associations arise as a consequence or cause of germ cell failure is still not certain.     

Evolutionary conservation of the human homologue of the yeast cell cycle control gene cdc2 and assignment of Cd2 to chromosome 10

Summary The human homologue of the fission yeast Schizosaccharomyces pombe cell cycle control gene cdc2 has been assigned to chromosome 10. DNA hybridization reveals that this gene is highly conserved in vertebrates. The human CDC2 gene probe detects a simple two-allele polymorphism in Taq1-digested DNA.     

Molecular organisation of the quinic acid utilization (QUT) gene cluster in Aspergillus nidulans

Summary The functional integrity of the QUTB gene (encoding quinate dehydrogenase) has been confirmed by transformation of a qutB mutant strain. The DNA sequence of the contiguous genes QUTD (quinate permease), QUTB and QUTG (function unknown) has been determined and analysed, together with that of QUTE (catabolic 3-dehydroquinase). The QUTB sequence shows significant homology with the shikimate dehydrogenase function of the complex AROM locus of Aspergillus nidulans, and with the QA-3 quinate dehydrogenase and QA-1S (repressor) genes of Neurospora crassa. The QUTD gene shows strong homology with the N. crassa QA-Y gene and QUTG with the QA-X gene. QUTD, QUTB, and QUTG, QUTE form two pairs of divergently transcribed genes, and conserved sequence motifs identified in the two common 5 non-coding regions show significant homology with UAS _GAL and UAS _QA sequences of the Saccharomyces cerevisiae and N. crassa Gal and QA systems. In addition, conserved 5 sequences homologous to the mammalian CAAT box are noted and a previously unreported conserved 22 nucleotide motif is presented.     

Developmentally regulated antigen associated with calcium crystals in tobacco anthers

We have found and characterized an antigen associated with crystal-containing cells in the stomium and connective tissue of the anthers of Nicotiana tabacum L. (tobacco). The antigen, defined by the monoclonal antibody NtF-8B1, localizes to subcellular regions surrounding the crystals. At the light-microscope level, the antigen is detectable just after the first appearance of crystals in the connective tissue of the anther, and at approximately the same time as the appearance of crystals in the stomium. The antigen is not detectable on a Western blot, and gave inconclusive results on a test of periodate sensitivity. It is not the crystals themselves, nor is the presence of the crystals required for antibody recognition. The antigen is sensitive to heat and protease treatment, indicating that it is a protein. The antigen is not tightly membrane-bound, in spite of its localization closely surrounding the crystals. Chemical tests indicate that the druse crystals in the stomium are calcium oxalate.Abbreviations ELISA enzyme-linked immunosorbent assay - FITC fluorescein isothiocyanate This research was supported by a National Science Foundation postdoctoral fellowship to B.L.H., by National Science Foundation grants DMB-87-15799 and to W.E.F. BSR-88-18035, and by U.S. Department of Agriculture grant GAM-89-01056. The authors thank Phillip T. Evans (Louisiana State University, Baton Rouge, USA), Wilma L. Lingle, Harry T. Horner, Jr. (Iowa State University), and A. Jack Fowler, Jr., for advice and helpful discussions.     

Cofactor interactions and the regulation of glutamate decarboxylase activity

More than 50% of glutamate decarboxylase (GAD) in brain is present as apoenzyme. Recent work has opened the possibility that apoGAD can be studied in brain by labeling with radioactive cofactor. Such studies would be aided by a compound that inhibits specific binding. One possibility is 4-deoxy-pyridoxine 5-phosphate, a close structural analog of the cofactor pyridoxal 5-phosphate. The effects of deoxypyridoxine-P on the cyclic series of reactions that interconverts apo- and holoGAD was investigated and found to be consistent with simple competitive inhibition of the activation of apoGAD by pyridoxal-P. As expected from the cycle GAD was inactivated when incubated with glutamate and deoxypyridoxine-P even though cofactor was present, but no inactivation was observed with deoxypyridoxine-P in the absence of glutamate. Deoxypyridoxine-P also stabilized apoGAD against heat denaturation. These effects were quantitatively accounted for by a kinetic model of the apo-holoGAD cycle. Deoxypyridoxine-P inhibited the labeling by [³²P]pyridoxal-P of GAD isolated from rat brain. Hippocampal extracts were labeled with [³²P]pyridoxal-P and analyzed by SDS-polyacrylamide gel electrophoresis. Remarkably few bands were strongly labeled. The major labeled band (at 63 kDa) corresponded to one of the forms of GAD. Other strongly-labeled bands were observed at 65 kDa (corresponding to the higher molecular weight form of GAD) and at 69–72 kDa. Labeling of the 63- and 65-kDa bands was inhibited by deoxypyridoxine-P, but the 69–72 kDa bands were unaffected, suggesting that the latter were non-specifically labeled. The results suggest that the 63-kDa form of GAD makes up the majority of apoGAD in hippocampus.Special issue dedicated to Dr. Eugene Roberts.     

Isolation and characterization of a mutant of L1210 murine leukemia deficient in nitrobenzylthioinosine-insensitive nucleoside transport

L1210 mouse leukemia cells exhibit two distinct types of nucleoside transport activity that have similar kinetic properties and substrate specificity, but differ markedly in their sensitivity to the inhibitor nitrobenzylthioinosine (NBMPR) (Belt, J. A. (1983) Mol. Pharmacol. 24, 479-484). It is not known whether these two transport activities are mediated by a single protein or by separate and distinct nucleoside transport proteins. We have isolated a mutant from the L1210 cell line that has lost the NBMPR-insensitive component of nucleoside transport, but retains NBMPR-sensitive transport. In the parental cell line 20-40% of the nucleoside transport activity is insensitive to 1 microM NBMPR. In the mutant, however, uridine and thymidine transport are almost completely inhibited by NBMPR. Consistent with the loss of NBMPR-insensitive transport, the mutant cells can be protected from the toxic effects of several nucleoside analogs by NBMPR. In contrast, the toxicity of the same analogs in the wild type cells is not significantly affected by NBMPR, presumably due to uptake of the nucleosides via the NBMPR-insensitive transporter. On the other hand, NBMPR-sensitive transport in the mutant appears to be unaltered. The mutant is not resistant to cytotoxic nucleosides in the absence of NBMPR and the cells retain the wild type complement of high affinity binding sites for NBMPR. Furthermore, the affinity of the binding site for the inhibitor is similar to that of parental L1210 cells. These results suggest that NBMPR-sensitive and NBMPR-insensitive nucleoside transport in L1210 cells are mediated by genetically distinct proteins. To our knowledge this is the first report of a mutant deficient in NBMPR-insensitive nucleoside transport.