De novo variants in CDK13 associated with syndromic ID/DD: Molecular and clinical delineation of 15 individuals and a further review.

De novo variants in the gene encoding cyclin-dependent kinase 13 (CDK13) have been associated with congenital heart defects and intellectual disability (ID). Here, we present the clinical assessment of 15 individuals and report novel de novo missense variants within the kinase domain of CDK13. Furthermore, we describe 2 nonsense variants and a recurrent frame-shift variant. We demonstrate the synthesis of 2 aberrant CDK13 transcripts in lymphoblastoid cells from an individual with a splice-site variant. Clinical characteristics of the individuals include mild to severe ID, developmental delay, behavioral problems, (neonatal) hypotonia and a variety of facial dysmorphism. Congenital heart defects were present in 2 individuals of the current cohort, but in at least 42% of all known individuals. An overview of all published cases is provided and does not demonstrate an obvious genotype-phenotype correlation, although 2 individuals harboring a stop codons at the end of the kinase domain might have a milder phenotype. Overall, there seems not to be a clinically recognizable facial appearance. The variability in the phenotypes impedes an à vue diagnosis of this syndrome and therefore genome-wide or gene-panel driven genetic testing is needed. Based on this overview, we provide suggestions for clinical work-up and management of this recently described ID syndrome.

The filamentous hemagglutinin of Bordetella parapertussis is the major adhesin in the phase-dependent interaction with NCI-H292 human lung epithelial cells.

Bordetella parapertussis is a Gram-negative bacterium which colonizes the human respiratory tract and can cause whooping cough or pertussis. This pathogen is subject to phase variation and expresses a series of virulence factors exclusively in the Bvg+ phase. Here, it is demonstrated for the first time that only the Bvg+ phase of B. parapertussis adheres to and invades the human lung epithelial cell line NCI-H292. A B. parapertussis mutant defective in expression of the Bvg+-regulated filamentous hemagglutinin (FHA) showed reduced binding (77% reduction) to NCI-H292 cells, as did a FHA mutant of the related Bordetella pertussis (85% reduction). In contrast to B. pertussis, binding of B. parapertussis to NCI-H292 cells was not inhibited by heparin, suggesting differences in the FHA adhesin and its host-cell receptor between these two species. Thorough understanding of the mechanism of action of the B. parapertussis virulence factors, such as FHA, is of particular interest in the development of novel strategies of pertussis vaccination.

Bordetella bronchiseptica has a BvgAS-controlled cytotoxic effect upon interaction with epithelial cells.

The interaction between the respiratory pathogen Bordetella bronchiseptica and epithelial cells was studied. After 2-3 h, B. bronchiseptica strains exerted a strong cytotoxic effect on HeLa cells which was evident by rounding of the cells and detachment from the substrate and which ultimately resulted in total disintegration of the host cell. Production of this cytotoxic activity appeared to be regulated by the BvgAS sensory transduction system, which coordinately regulates many B. bronchiseptica virulence factors, since bacteria cultured in the presence of sulfate anions, inhibitors of the BvgAS response, did not exhibit this effect. Furthermore, spontaneous phase variants of B. bronchiseptica strains adhered to HeLa cells but were not cytotoxic. The cytotoxic component is presumably not secreted because the bacterial culture supernatant was not cytotoxic for HeLa cells. Besides HeLa cells other human epithelial cell lines such as Chang cells, larynx HEp-2 cells and lung NCI-H292 cells were sensitive to the cytotoxic activity of B. bronchiseptica. These results suggest the presence of a novel BvgAS-regulated virulence factor in B. bronchiseptica.

Mutational analysis of the Bordetella pertussis fim/fha gene cluster: identification of a gene with sequence similarities to haemolysin accessory genes involved in export of FHA.

The chromosome of Bordetella pertussis harbours a region of 27 contiguous kb, which contains the bvg, fha and fim genes, involved in the co-ordinate regulation of virulence genes, FHA production and fimbriae production, respectively. The linkage of FHA and fimbrial genes has resulted in some confusion concerning the existence and location of genes required for the production of FHA and the function of the fimbrial genes fimB-D, which were proposed to be involved in both FHA and fimbriae biosynthesis. Through the use of non-polar mutations in each of these genes, we found that fimB-D are required for the production of both serotype 2 and 3 fimbriae, but not for FHA biosynthesis. Furthermore, a large open reading frame, designated fhaC, was identified downstream of fimD. It was shown that fhaC is essential for FHA production but not for fimbriae biogenesis. We propose that insertion mutations in fimB-D affect FHA production because of polar effects on fhaC expression. An insertion in the region downstream of fhaC had only a slight effect on FHA and fimbriae production. The fhaC gene product shows homology with ShIB and HpmB, two outer membrane proteins involved in export and activation of the haemolysins, ShIA and HpmA, of Serratia marcescens and Proteus mirabilis, respectively. Homology is also observed between the N-termini of FHA, ShIA and HpmA. Export of the haemolysins requires the N-termini of these molecules, and when this region was removed from FHA by an in-frame deletion, FHA biosynthesis was abolished. These results suggest that the N-terminus of FHA interacts with FhaC, and that as a result FHA is transported across the outer membrane.

Detection of HIV antibodies in saliva as a tool for epidemiological studies.

OBJECTIVE: To evaluate the use of saliva specimens for the detection of HIV antibodies among high-risk groups in epidemiological studies. DESIGN: Testing of saliva specimens collected by different methods from individuals with known HIV status. The most reliable method was examined for its usefulness in a field study among a high-risk group. METHODS: Saliva samples were obtained either by using a cotton-wool roll ('Salivette') or as 'whole saliva'. HIV antibodies were determined using commercial enzyme-linked immunosorbent assays (ELISA). Confirmation was performed using a line immunoassay or an immunoblot assay. RESULTS: In 'Salivette' samples, HIV antibodies were detected by ELISA in seven out of 22 seropositive individuals. In contrast, testing of 'whole saliva' samples from 79 HIV-seropositive and 115 HIV-seronegative individuals resulted in a 100% correlation with HIV serum status. The positive reaction of 20 'whole saliva' specimens was confirmed in a line immunoassay, whereas in an immunoblot assay only seven specimens were positive, one negative, and 12 indeterminate. In an HIV prevalence study among drug users, 395 'whole saliva' samples were tested in two different ELISA. Both assays showed complete agreement in detecting 58 positive and 337 negative samples. All positive samples were confirmed by the line immunoassay. CONCLUSION: Our study demonstrates that 'whole saliva' specimens are a good alternative to blood samples in epidemiological studies of HIV prevalence in high-risk groups.

Proteolytic activation of a bovine brain protein with phosphatidylinositol transfer activity.

We have purified a 38 kDa protein from bovine brain which is cross-reactive with an affinity purified antibody against the 35 kDa phosphatidylinositol transfer protein from the same source. Controlled trypsinization of the 38 kDa protein yielded an immunoreactive protein of 35 kDa which displayed a 6-fold increase in phosphatidylinositol transfer activity and a 10-fold higher affinity for this phospholipid. The possibility that the 38 kDa protein is a precursor of the phosphatidylinositol transfer protein is discussed.