Recurrent proximal 18p monosomy and 18q trisomy in a family with a maternal pericentric inversion of chromosome 18

We report a recurrent partial monosomy of 18p10-->11.2 and proximal partial trisomy of 18q10-->21.3 caused by a maternal pericentric inversion of chromosome 18, involving breakpoints p11.2 and q21q21.3 Based on cytogenetics and FISH analysis, we speculate that the recurrent chromosome abnormality in the proband and in the fetus was the result of a translocation, possibly in a germ cell or germ cell precursor, between the maternal normal 18 and her inverted 18, resulting in maternal germinal mosaicism, i.e. 46,XX,inv(18)/46,XX,t[18;inv(18)][q10;q10]. The unbalanced karyotype of the proband and the fetus is 46,XY,+18,der[18;inv(18)][q10;q10]. To the best of our knowledge, there are no reports of this combination of proximal 18p monosomy and proximal 18q trisomy. The other interesting observation was association of Hirschsprung's disease in the proband.     

Partial trisomy 18q in a newborn with typical 18 trisomy phenotype

Summary This paper describes a case of partial trisomy of almost the entire long arm of chromosome 18 in a newborn with classic trisomy-18 phenotype, resulting from a de novo unbalanced 18q/21p translocation: karyotype: 46,XX,-21,t(18;21)(18qter18q11::21p1221qter). A review of the other reported cases of partial trisomy 18 suggests that a critical segment in chromosome 18, corresponding to bands q11-q12, might be responsible for most of the signs of trisomy 18, including failure to thrive and early death.     

A time-resolved fluoroimmunoassay for 18-oxocortisol and 18-hydroxycortisol. Development of a monoclonal antibody to 18-oxocortisol

Patients with primary aldosteronism and with glucocorticoid-suppressible aldosteronism excrete in the urine excessive amounts of the hybrid steroids 18-hydroxycortisol and 18-oxocortisol. The measurement of these steroids aids in the differential diagnosis of various adrenal disorders. We have produced mouse monoclonal antibodies against 18-oxocortisol and polyclonal antibodies against 18-hydroxycortisol and describe a time-resolved fluoroimmunoassay (TR-FIA) technique for the measurement of these steroids in the urine. We have also compared this assay with an ELISA technique for these compounds. We also describe the preparation of in-house Eu(III)-labeled avidin and an enhancement solution and compared to a commercially available Eu(III)-labeled streptavidin and enhancement solutions. The monoclonal antibodies against 18-oxocortisol are sensitive and have a high level of specificity. The TR-FIA technique using in-house prepared reagents or commercial ones were indistinguishable from each other, but at a significant saving. The TR-FIA technique was more sensitive and had a greater precision than the ELISA technique for both steroids.     

Prenatal diagnosis of a de novo satellited chromosome 18 (18ps) associated with 18p deletion

De novo satellited non-acrocentric chromosomes are very rare findings in prenatal diagnosis. Here we report the first case of a de novo 18ps, associated with del(18p), detected at prenatal diagnosis. A 37 years old woman underwent Chorionic Villus Sampling (CVS) for advanced maternal age. Cytogenetic analysis on direct CVS preparation (CVSc) revealed a male karyotype with a nonfamilial satellited 18ps and a reciprocal translocation t(17;19)(P11.1;q11) of maternal origin. The mesenchimal CVS culture (CVSm) showed a mosaic of cell lines with various involvement of chromosome 18: 18ps [36/70]/ r(18) [25/70]/ del(18p) [3/70]/ -18 [6/70]. Amniotic fluid cells (AFC) confirmed the homogeneous karyotype found at CVSc. The molecular cytogenetic characterization, performed on AFC, allowed the following diagnosis: 46,XY, +15, dic(15;18)(p11.1;p11.2), t(17;19)(p11.1;q11)mat. ish dic(15;18)(tel 18p-, D15Z1+, wcp18-, wcp 18+, D18Z1+, tel 18q+). The foetal autopsy disclosed subtle facial dysmorphisms and corpus callosum hypoplasia. In case of prenatal detection of de novo terminal ectopic NORs an accurate cytogenetic and molecular analysis should be performed in order to rule out subtle unbalancements.     

Interleukin-18, a proinflammatory cytokine

Although IL-18 is an inducer of IFN-gamma and Th1 responses. IL-18 is a proinflammatory cytokine by several criteria. In several animal models. antibodies that neutralize endogenous IL-18 reduce the severity of disease. Endotoxin lethality is prevented by anti-IL-18. Even in models that are interferon-y independent, neutralization of IL-18 prolongs survival. Anti-IL-18 also protects the liver against cellular injury induced by toxins or activated T cells. In models of hepatic melanoma metastasis. IL-18 blockade reduces the adherence of malignant cells by preventing IL-18 upregulation of vascular endothelial adhesion-1 molecule expression. IL-18 and IL-12 act synergistically to stimulate I cells and natural killer cells to produce IFN-gamma but neutralization of IL-18 prevents IL-12 induction of IFN-gamma. IL-18. like several cytokines. can be used to enhance host defense against tumors in mice a mechanism that is most often IFN-gamma-dependent. Nevertheless. it is the proinflammatory portfolio of IL-18 which likely contributes to enhanced host defenses. In models or arthritis, lung injury or inflammatory bowel disease, neutralization of IL-18 reveals the important role of this cytokine in mediating inflammation.     

Rab18 and a Rab18 GEF complex are required for normal ER structure

The ancestral Rab GTPase Rab18 and both subunits of the Rab3GAP complex are mutated in the human neurological and developmental disorder Warburg Micro syndrome. Here, we demonstrate that the Rab3GAP complex is a specific Rab18 guanine nucleotide exchange factor (GEF). The Rab3GAP complex localizes to the endoplasmic reticulum (ER) and is necessary for ER targeting of Rab18. It is also sufficient to promote membrane recruitment of Rab18. Disease-associated point mutations of conserved residues in either the Rab3GAP1 (T18P and E24V) or Rab3GAP2 (R426C) subunits result in loss of the Rab18 GEF and membrane-targeting activities. Supporting the view that Rab18 activity is important for ER structure, in the absence of either Rab3GAP subunit or Rab18 function, ER tubular networks marked by reticulon 4 were disrupted, and ER sheets defined by CLIMP-63 spread out into the cell periphery. Micro syndrome is therefore a disease characterized by direct loss of Rab18 function or loss of Rab18 activation at the ER by its GEF Rab3GAP.     

18q- Syndrome resulting from a tdic(14p;18q)

Summary A case of 18q- syndrome due to a de novo tdic(14p;18q) is presented. The interest of this observation lies in the rarity of stable dicentric chromosomes arising from reciprocal translocations between autosomes.     

The production of a monoclonal antibody to 18-hydroxycortisol and other 18-hydroxylated steroids

Four strains of mice were immunized with 6 different conjugates of 3-O (carboxymethyl-oximino)-18-hydroxycortisol to bovine serum albumin (3 preparations), turkey serum albumin, porcine thyroglobulin, and keyhole limpet hemocyanin. Spleens from 7 of 48 mice immunized were fused with Fox/NY and/or HL-1 Friendly myeloma cell lines, yielding many positive clones for antibody formation. Short cross-reactivities were done in 293 culture supernatants and were found to have low cross-reactivity (less than 0.001%) to cortisol, but very high cross-reactivity to 18-hydroxy-11-deoxycortisol (70 to 140%). One clone showed over 100% cross-reactivity with all the 18-hydroxylated steroids studied. The major problem encountered in the generation of monoclonal antibodies was the low antibody response in the vast majority of mice injected. Half the mice developed no measurable titer, and the clones evaluated from those that did produce antibodies cross-reacted with other 18-hydroxylated steroids. Nevertheless, the antibody developed could serve in radioimmunoassay for 18-hydroxy-11-deoxycortisol separated chromatographically from other cross-reacting steroids. This is important as no synthetic 18-hydroxy-11-deoxycortisol is available.     

Production of a biologically active human interleukin 18 requires its prior synthesis as PRO-IL-18

Interleukin (IL-)18 is an activator of NK cells and a co-inducer of Th(1)cytokines, sharing structural features with the IL-1 family of proteins. Unlike most other cytokines, IL-18 and IL-1beta lack a signal peptide, have an all beta-pleated sheet structure and are synthesized as biologically inactive precursors (pro-IL-18 and pro-IL-1beta). These precursors are cleaved by caspase-1 (IL-1beta-converting enzyme, ICE) to form the biologically active mature cytokines. Direct expression of mature recombinant human IL-18 in E. coli resulted in a partially active cytokine. We tested the possibility that correct folding of huIL-18 requires its prior synthesis as pro-IL-18. Because caspase-1 is not readily available, we constructed an expression vector encoding human pro-IL-18 in which the caspase-1 cleavage site was mutated into a factor Xa site. To facilitate purification, the mutated pro-IL-18 cDNA was fused in frame to a glutathione-S-transferase (GST) coding sequence. The GST-pro-IL-18 fusion protein was expressed in E. coli, captured on glutathione agarose and mature human IL-18, exhibiting high biological activity was released upon cleavage with factor Xa. This result indicates that correct folding of huIL-18 occurs at the level of pro-IL-18 and provides a practical way to produce biologically active huIL-18.     

Identification of a critical Ig-like domain in IL-18 receptor alpha and characterization of a functional IL-18 receptor complex

Steady state mRNA levels in various human tissues reveal that the proinflammatory cytokine IL-18 is constitutively and ubiquitously expressed. However, limited IL-18R alpha-chain (IL-18Ralpha) expression in tissues may restrict ligand-acting sites and contribute to a specific response for IL-18. To study the IL-18R complex, [(125)I]IL-18 was studied for binding to the cell surface receptors of IL-18-responsive NK and macrophagic KG-1 cells. After cross-linking, [(125)I]IL-18 formed three IL-18R complexes with sizes of approximately 93, 160, and 220 kDa. In KG-1 cells, Scatchard analysis revealed the presence of 135 binding sites/cell, with an apparent dissociation constant (K(d)) of 250 pM; in NK cells, there were 350 binding sites per cell with an apparent K(d) of 146 pM. Each domain of extracellular IL-18Ralpha was cloned and individually expressed in Escherichia coli. An mAb specifically recognized the membrane-proximal third domain; this mAb blocked IL-18-induced IFN-gamma production in NK cells. Furthermore, deletion of the membrane-proximal third domain of IL-18Ralpha prevented the formation of IL-18R ternary complex with IL-18R beta-chain. The present studies demonstrate that the biologically active IL-18R complex requires the membrane-proximal third Ig-like domain in IL-18Ralpha for the formation of IL-18R ternary complex as well as for signal transduction involved in IL-18-induced IFN-gamma in NK cells.     

Cloning and characterization of rhesus IL-18 binding protein,a natural antagonist to IL-18

IL-18 is a proinflammatory cytokine that is important for host defense, but is also involved in the pathogenesis of a number of disease processes, ranging from autoimmune disorders to atherosclerosis. IL-18 binding protein (IL-18BP) is a constitutively expressed glycoprotein that specifically neutralizes the effects of IL-18, resulting in decreased production of IFN-γ and reduction in Th1 immune responses. In this study we cloned and sequenced a full-length cDNA of the rhesus IL-18BP (RhIL-18BP) from the spleen of rhesus macaques (Macaca mulatta) and compared its nucleotide and amino acid sequences to the functional murine and human IL-18BP orthologues. In addition, we fused RhIL-18BP to the Fc portion of human IgG1 to make recombinant RhIL-18BP·Fcγ1 in order to facilitate its detection by Western blot analysis and determined the approximate molecular weight of RhIL-18BP·Fcγ1 to be 66 kD. With this fusion protein, we showed that RhIL-18BP was functional and could significantly reduce murine IL-18 and LPS-induced IFN-γ production by murine splenocytes. Furthermore, we demonstrated the expression of IL-18BP in atherosclerotic lesions in a rhesus model of atherosclerosis, underscoring the need to fully understand the role of this protein as a primary negative regulator of IL-18 in multiple disease processes.