Mutations of CD40 ligand in two patients with hyper-IgM syndrome

Two patients with the X-linked form of the hyper-IgM syndrome have been studied. Both patients present: 1. Mutations in the CD40L gene (a nonsense point mutation that introduces a termination codon at the extracellular domain of the protein, and a deletion that eliminates exon 4 as consequence of an abnormal splicing). 2. Lack of CD40L expression on the lymphocyte surface after stimulation with ionomycin and PMA. 3. Altered lymphocytic proliferation in response to anti-CD3. 4. Hyper IgM, low IgG and IgA levels and neutropenia. One of the patients shows, in addition, low Natural Killer cell numbers and severe herpetic infections, which distinguishes this case from the common hyper-IgM syndrome phenotype. Finally, a hyper-IgM stable phenotype has been immortalized by Herpes virus Saimiri for the first time.     

Chemoattractant-induced NADPH oxidase activity in human monocytes is terminated without any association of receptor-ligand complex to cytoskeleton

When the chemotactic peptide formylmethionyl-leucyl-phenylalanine binds to its cell surface receptor, a transmembrane signal is generated that activates the superoxide-producing NADPH oxidase of human phagocytes. Comparing monocytes and neutrophils with regard to the production of superoxide anion induced by the peptide, we found a similar time-course for both types of cells. In neutrophils, ligand binding induced a conversion of the receptor to a high-affinity form, a change suggested to be due to an association of the receptor-ligand complex to the Triton X-100-insoluble cytoskeleton. This event has been hypothesized to terminate the signal that activates the NADPH oxidase and thereby results in cessation of the cellular production of superoxide anion. Neutrophils preincubated with the cytoskeleton-disrupting drug cytochalasin B showed an increased and prolonged superoxide anion production after activation with the peptide, thus indicating that the cytoskeleton is involved in terminating this response. Formylmethionyl-leucyl-phenylalanine was also found to induce polymerization of actin in monocytes; however, cytochalasin B had no effect on the peptide-induced generation of superoxide anion in these cells. Furthermore, also in monocytes, ligand binding induced a conversion of the receptor to a high-affinity form; however, the receptor-ligand complex did not coisolate with the Triton X-100-insoluble cytoskeleton. These results indicate that, in monocytes, the NADPH oxidase activating pathway is terminated without any association of the receptor-ligand complex to the Triton X-100-insoluble cytoskeleton.     

Training in clinical genetics and genetic counseling in Asia

The status of training in clinical genetics and genetic counseling in Asia is at diverse stages of development and maturity. Most of the training programs are in academic training centers where exposure to patients in the clinics or in the hospital is a major component. This setting provides trainees with knowledge and skills to be competent geneticists and genetic counselors in a variety of patient care interactions. Majority of the training programs combine clinical and research training which provide trainees a broad and integrated approach in the diagnosis and management of patients while providing opportunities for research discoveries that can be translated to better patient care. The background on how the training programs in clinical genetics and genetic counseling in Asia evolved to their current status are described. Each of these countries can learn from each other through sharing of best practices and resources.     

Central nervous system involvement in arthrogryposis multiplex congenita: Overview of causes,diagnosis, and care

Arthrogryposis or AMC, arthrogryposis multiplex congenita, is defined as multiple congenital joint contractures in more than two joints and in different body areas. The common cause of all AMC is lack of movement in utero, which in turn can have different causes, one of which is CNS involvement. Intellectual disability/CNS involvement is found in approximately 25% of all AMC. AMC with CNS involvement includes a large number of genetic syndromes. So far, more than 400 genes have been identified as linked to AMC, with and without CNS involvement. A number of neonatally lethal syndromes and syndromes resulting in severe disability due to CNS malfunction belong to this group of syndromes. There are several X‐linked disorders with AMC, which are primarily related to intellectual disability. A number of neuromuscular disorders may include AMC and CNS/brain involvement. Careful clinical evaluation by a geneticist and a pediatrician/pediatric neurologist is the first step in making a specific diagnosis. Further investigations may include MRI of the brain and spinal cord, electroencephalogram, blood chemistry for muscle enzymes, other organ investigations (ophtalmology, cardiology, gastrointestinal, and genitourinary systems). Nerve conduction studies, electromyogram, and muscle pathology may be of help when there is associated peripheral nervous system involvement. But most importantly, genetic investigations with targeted or rather whole exome or genome sequencing should be performed. A correct diagnosis is important in planning adequate treatment, in genetic counselling and also for future understanding of pathogenic mechanisms and possible new treatments. A multidiciplinary team is needed both in investigation and treatment.     

Agouti-related peptide-expressing neurons are mandatory for feeding

Multiple hormones controlling energy homeostasis regulate the expression of neuropeptide Y (NPY) and agouti-related peptide (AgRP) in the arcuate nucleus of the hypothalamus. Nevertheless, inactivation of the genes encoding NPY and/or AgRP has no impact on food intake in mice. Here we demonstrate that induced selective ablation of AgRP-expressing neurons in adult mice results in acute reduction of feeding, demonstrating direct evidence for a critical role of these neurons in the regulation of energy homeostasis.     

Comparative study in the Ames test of benzo[a]pyrene and 2-aminoanthracene metabolic activation using rat hepatic S9 and hepatocytes following in vivo or in vitro induction

We studied the replacement of hepatic S9 with in vivo and in vitro induced hepatocytes as a metabolic activation system with the aim of broadening the possibilities of mutagenic assays. Rats were pretreated with beta-naphthoflavone (BNF), phenobarbital (PB), 3-methylcholanthrene (MC) and a combination of BNF and PB (BNF + PB). Mutagenic activation of benzo[a]pyrene (BP) and 2-aminoanthracene (2AA) by hepatic S9 and hepatocytes was determined in the Ames test. Primary rat hepatocytes were used for in vitro induction and were used as the activating system in the Ames test. In vivo BNF treatment greatly increased the metabolic activation capacity of hepatic S9 and hepatocytes towards BP. With regard to 2AA activation, S9 and hepatocytes showed different BNF induction profiles. PB treatment reduced the mutagenicity of both compounds. Although ethoxyresorufin O-dealkylase (EROD) activity of S9 from BNF + PB-treated animals was almost 30-fold greater than the control, its effectiveness in activation of 2AA was below the control level. A large part of the EROD activity of control cells was lost during culture, together with the ability to activate 2AA, however, 72 h of MC induction increased EROD activity to 200-fold of the control, which corresponds to 28% of that of in vivo induced hepatocytes. The mutagenic potential of BP activated by in vitro induced hepatocytes was 10-fold above the control, which is 47% of the mutagenicity detected following in vivo induction. In vitro induced hepatocytes increased 2AA mutagenicity to 14.6-fold over the control, which corresponds to 68% of in vivo induction. Our results suggest that primary culture of hepatocytes provides a useful model for the study of the role of metabolic activation processes concerning enzyme activity of cytochromes P450 and other metabolic enzymes and induction profiles of different inducers.     

An intact heavy chain at the actin-subfragment 1 interface is required for ATPase activity of scallop myosin

Summary Scallop S1 has a region sensitive to tryptic hydrolysis not found thus far in S1s of other species, located 65K from theN-terminus as determined by SDS/polyacrylamide-gel electrophoresis. In the presence of actin the S1 heavy chain is preferentially cleaved at this site. The high-salt EDTA and calcium ATPase activities of the nicked 65K–31K S1 are abolished. This inactivation is not due to denaturation, conformational effects of actin, or to light chain dissociation. The unique proteolytic site of scallop S1 is adjacent to a peptide involved in actin-S1 interaction in scallop and rabbit but it is far removed from the nucleotide-binding site in the linear amino acid sequence. We conclude that proteolysis inactivates the high-salt ATPase activities through a connection mediated by tertiary interactions. Such a connection provides a structural correlate for the known reciprocal relationship between the nucleotide and actin affinities of myosin.Abbreviations S1 papain subfragment 1 containing both light chains - S1^–LC papain subfragment 1 prepared in the absence of bound regulatory light chain containing only a part of the essential light chain and having a shorter heavy chain - HC heavy chain - LC light chain - DTT dithiothreitol - TLCK 7-amino-1-chloro-3-l-tosylamidoheptan-2-one - TPCK 1-chloro-4-phenyl-3-l-toluene-p- sulphonamidobutan-2-one - K kilodalton     

New phenotypic, functional and electrophysiological characteristics of KG-1 cells

Myeloid dendritic cells (DC) are representatives of a rare and phenotypically diverse population of professional antigen presenting cells possessing high functional heterogeneity and flexibility. Here we studied the phenotypic, functional and electrophysiological characteristics of KG-1 cells, an erythroleukemia model cell line, which shares morphological and physiological similarities with immature and mature myeloid DC. We compared the expression of internalizing receptors and other cell surface molecules, antigen uptake and migration of unstimulated and activated KG-1 cells with the characteristics of immature and mature DC. Unstimulated KG-1 cells were less potent in capturing extracellular materials than immature DC. In contrast to monocyte-derived DC KG-1 cells stimulated by PMA and ionomycin ceased to migrate along the MIP-3beta chemokine gradient despite their high expression of CCR7 chemokine receptor and MDR, a transporter implicated in DC migration. Moreover, we determined the ion channel repertoire of KG-1 cells before and after treatment with PMA and ionomycin by using the patch-clamp technique. We found that both unstimulated and activated KG-1 cells expressed time- and voltage-independent, ChTx sensitive intracellular Ca(2+)-gated potassium conductance suggesting the presence of K(Ca) channels in their membranes. Based on our results we propose that KG-1 cells resemble myeloid DC but also possess unique phenotypic, functional and electrophysiological characteristics.     

Oncogene-induced basement membrane invasiveness in human mammary epithelial cells

Expression of the intermediate filament protein vimentin, and loss of the cellular adhesion protein uvomorulin (E-cadherin) have been associated with increased invasiveness of established human breast cancer cell linesin vitro andin vivo. In the current study, we have further examined these relationships in oncogenically transformed human mammary epithelial cells. A normal human mammary epithelial strain, termed 184, was previously immortalized with benzo[a]pyrene, and two distinct sublines were derived (A1N4 and 184B5). These sublines were infected with retroviral vectors containing a single or two oncogenes of the nuclear, cytoplasmic, and plasma membrane-associated type (v-ras ^H, v-ras ^Ki, v -mos, SV40T and c -myc). All infectants have been previously shown to exhibit some aspects of phenotypic transformation. In the current study, cellular invasiveness was determinedin vitro using Matrigel, a reconstituted basement membrane extract. Lineage-specific differences were observed with respect to low constitutive invasiveness and invasive changes after infection withras, despite similarras-induced transformation of each line. Major effects on cellular invasiveness were observed after infection of the cells with two different oncogenes (v-ras ^H + SV40T and v -ras ^H + v -mos). In contrast, the effects of single oncogenes were only modest or negligible. All oncogenic infectants demonstrated increased attachment to laminin, but altered secretion of the 72 kDa and 92 kDa gelatinases was not associated with any aspect of malignant progression. Each of the two highly invasive double oncogene transformants were vimentinpositive and uvomorulin-negative, a phenotype indicative of the epithelial-mesenchymal transition (EMT) previously associated with invasiveness of established human breast cancer cell lines. Weakly invasive untransformed mammary epithelial cells in this study were positive for both vimentin and uvomorulin, suggesting that uvomorulin may over-ride the otherwise vimentin-associated invasiveness.