Missense mutation and hexanucleotide duplication in the PAX2 gene in two unrelated families with renal-coloboma syndrome (MIM 120330)

We present a family with autosomal-dominant inheritance of renal insufficiency caused by renal hypoplasia in six individuals. In all affected individuals, signs of optic disk dysplasia were detected, but most patients were asymptomatic. A heterozygous missense mutation in the PAX2 gene causing a Gly75 to Ser substitution was present in all affected individuals. A second, unrelated patient presented with ocular complaints related to optic disk dysplasia, and had a history of vesico-ureteral reflux. A heterozygous hexanucleotide duplication in the PAX2 gene was detected leading to the duplication of GluThr at positions 74 and 75. The mutations in these two families are the first mutations in the PAX2 gene that do not lead to a truncated protein. Mechanistically, these mutations are expected to result in abnormal folding of the PAX2 protein. These observations further expand the spectrum of clinical features associated with PAX2 mutations, and suggest that a distinct genetic disorder can be identified in patients with renal dysplasia through a careful eye examination. As the ocular manifestations in this syndrome are variable anomalies of retinal and optic disk dysplasia, we prefer the term “papillo-renal syndrome”. Received: 29 January 1998 / Accepted: 25 March 1998     

An Avirulent Mutant of Rabies Virus Is Unable To Infect Motoneurons In Vivo and In Vitro

An antigenic double mutant of rabies virus (challenge virus standard [CVS] strain) was selected by successive use of two neutralizing antiglycoprotein monoclonal antibodies, both specific for antigenic site III. This mutant differed from the original virus strain by two amino acid substitutions in the ectodomain of the glycoprotein. The lysine in position 330 and the arginine in position 333 were replaced by asparagine and methionine, respectively. This double mutant was not pathogenic for adult mice. When injected intramuscularly into the forelimbs of adult mice, this virus could not penetrate the nervous system, either by the motor or by the sensory route, while respective single mutants infected motoneurons in the spinal cord and sensory neurons in the dorsal root ganglia. In vitro experiments showed that the double mutant was able to infect BHK cells, neuroblastoma cells, and freshly prepared embryonic motoneurons, albeit with a lower efficiency than the CVS strain. Upon further incubation at 37°C, the motoneurons became resistant to infection by the mutant while remaining permissive to CVS infection. These results suggest that rabies virus uses different types of receptors: a molecule which is ubiquitously expressed at the surface of continuous cell lines and which is recognized by both CVS and the double mutant and a neuron-specific molecule which is not recognized by the double mutant.     

Sexual size dimorphism in parasitic oxyurid nematodes

As in many invertebrates, female oxyurids are larger than male. Sexual size dimorphism (SSD) of oxyurid nematodes (the hosts of which are both invertebrate and vertebrate), is investigated regarding body size of both host and parasite. SSD of parasites appeared to be weakly, but not significandy, correlated with invertebrate and vertebrate host body size. However, this study reveals a different pattern for SSD with respect to either type of host. SSD does not increase in tandem with body size in vertebrate parasites either at the level of species or genus. SSD is much more pronounced in Syphaciidae than in Heteroxynematidae, two families of vertebrate parasites exhibiting different modes of transmission (members of the Syphaciidae are transmitted through perianal contamination). SSD is investigated in one monophyletic group of parasites of primates, for which a phylogeny is known. Independent comparisons method is used and we find that the body size of female parasite is strongly correlated with that of the male. The hypoallometry (slope<1) of the relationship suggests that the SSD is not linked to an increase of parasite body size. Moreover, there is no influence of host body size on parasite SSD. The pattern in parasites of invertebrates is different. First, SSD has been found to increase with parasite body size in two groups of invertebrate parasites: the oxyurids of Dictyoptera and Coleoptera. Second, female body size of invertebrate parasites is not correlated with male body size either at genus or species level. Finally, the evolution of SSD is discussed in relation to the demographic patterns of invertebrate parasites and the haplodiploid mode of reproduction of these parasitic nematodes.     

Dodecylphosphocholine micelles as a membrane-like environment: new results from NMR relaxation and paramagnetic relaxation enhancement analysis

To further examine to what extent a dodecylphosphocholine (DPC) micelle mimics a phosphatidylcholine bilayer environment, we performed ¹³C, ²H, and ³¹P NMR relaxation measurements. Our data show that the dynamic behavior of DPC phosphocholine groups at low temperature (12 °C) corresponds to that of a phosphatidylcholine interface at high temperature (51 °C). In the presence of helical peptides, a PMP1 fragment, or an annexin fragment, the DPC local dynamics are not affected whereas the DPC aggregation number is increased to match an appropriate area/volume ratio for accommodating the bound peptides. We also show that quantitative measurements of paramagnetic relaxation enhancements induced by small amounts of spin-labeled phospholipids on peptide proton signals provide a meaningful insight on the location of both PMP1 and annexin fragments in DPC micelles. The paramagnetic contributions to the relaxation were extracted from intra-residue cross-peaks of NOESY spectra for both peptides. The location of each peptide in the micelles was found consistent with the corresponding relaxation data. As illustrated by the study of the PMP1 fragment, paramagnetic relaxation data also allow us to supply the missing medium-range NOEs and therefore to complete a standard conformational analysis of peptides in micelles. Received: 16 April 1998 / Revised version: 19 June 1998 / Accepted: 30 July 1998     

Identification,Purification, and Characterization of Transpeptidase and Glycosyltransferase Domains of Streptococcus pneumoniae Penicillin-Binding Protein 1a

Resistance to β-lactam antibiotics in Streptococcus pneumoniae is due to alteration of penicillin-binding proteins (PBPs). S. pneumoniae PBP 1a belongs to the class A high-molecular-mass PBPs, which harbor transpeptidase (TP) and glycosyltransferase (GT) activities. The GT active site represents a new potential target for the generation of novel nonpenicillin antibiotics. The 683-amino-acid extracellular region of PBP 1a (PBP 1a*) was expressed in Escherichia coli as a GST fusion protein. The GST-PBP 1a* soluble protein was purified, and its domain organization was revealed by limited proteolysis. A protease-resistant fragment spanning Ser 264 to Arg 653 exhibited a reactivity profile against both β-lactams and substrate analogues similar to that of the parent protein. This protein fragment represents the TP domain. The GT domain (Ser 37 to Lys 263) was expressed as a recombinant GST fusion protein. Protection by moenomycin of the GT domain against trypsin degradation was interpreted as an interaction between the GT domain and the moenomycin.The synthesis of the bacterial cell wall requires cytoplasmic and periplasmic enzymes. The final steps of peptidoglycan biosynthesis occur outside the cytoplasmic membrane, and they are catalyzed by membrane-bound penicillin-binding proteins (PBPs). PBPs play essential roles in cell division and morphology (6, 20, 31). Based upon their molecular sizes and amino acid sequence similarities, PBPs can be classified into two groups (6): low-molecular-weight (low-M_r) PBPs, which act as d,d-carboxypeptidases, and high-molecular-weight (high-M_r) PBPs, which carry transpeptidase (TP) and glycosyltransferase (GT) activities. The high-M_r group can be further divided into bifunctional enzymes with TP and GT activities (class A) and monofunctional TP enzymes (class B).β-Lactam antibiotics bind with high affinity specifically to d,d-carboxypeptidase and TP domains because of their structural similarity to the natural substrates, the stem peptides. This binding results in the formation of a covalent acyl-PBP enzyme complex, leading to the inactivation of PBPs.High-M_r PBPs are multidomain proteins (6). The three-dimensional structure of Streptococcus pneumoniae PBP 2x (class B high-M_r PBP) illustrates this domain organization (25). The only non-penicillin-binding domain of known function is the GT domain, corresponding to the N-terminal region of class A PBPs. This GT activity, clearly identified in Escherichia coli PBP 1b, is difficult to measure (23, 29, 31–35). It is insensitive to penicillin but sensitive to moenomycin, an antibiotic which is not used for human therapy (23, 29, 32, 33).S. pneumoniae is one of the major human pathogens of the upper respiratory tract, causing pneumonia, meningitis, and ear infections. Six PBPs have been identified in S. pneumoniae: high-M_r PBPs 1a, 1b, 2a, 2x, and 2b and low-M_r PBP 3 (8). PBPs 1a, 1b, and 2a belong to class A, while PBPs 2x and 2b are monofunctional class B proteins. Deletion of pbp2x and pbp2b in S. pneumoniae is lethal for the bacteria, while the deletion of pbp1a is tolerated (11), probably due to compensation by PBP 1b. This has been observed for E. coli class A PBP 1a, whose deletion can be compensated for by PBP 1b (36). In clinical isolates of resistant pneumococci, pbp1a, pbp2x, and pbp2b genes were shown to present a mosaic organization, encoding PBPs with reduced affinity for β-lactam antibiotics (2, 5, 15, 18). The specific resistance to ceftriaxone and cefotaxime of S. pneumoniae from the hospital environment is mediated by modification of PBP 2x and PBP 1a (22). Furthermore, gene transfer of pbp1a, pbp2x, and pbp2b from resistant strains conferred penicillin resistance on sensitive S. pneumoniae strains under laboratory conditions (2–4, 14, 15, 27, 30).The effort to overcome resistance to antibiotics in S. pneumoniae might therefore benefit from a detailed understanding of the molecular basis of TP and GT activities. The GT domain represents a new potential target for novel nonpenicillin antibiotics. Here, we delineate the GT and TP domains of S. pneumoniae PBP 1a* (a water-soluble form of PBP 1a) by limited proteolytic digestion and expression of recombinant domains. The TP activity of PBP 1a* and that of the isolated TP domain were compared. We also present evidence for an interaction between the isolated GT domain and moenomycin.     

Microstructural and physico-chemical characterization of ‘centers of calcification’ in septa of some Recent scleractinian corals

In order to define the value of the concept of ‘center of calcification’, an attempt has been made to collect microstructural, physical, and chemical data from these particular structures. In each of the fifteen species studied, these data are compared with similar characteristics observed in the surrounding fibrous tissue. Results lead to a paradoxical conclusion. Although the existence of centers of calcification is sometimes denied, they have been evidenced by various techniques in septa of all the studied species, that belong to various families. Thus, ‘centers of calcification’ appear to be a basic component in the development of corallian septal architecture. But taking into account their microstructural and chemical peculiarities allows to introduce some changes in the current view concerning their role in skeletogenesis of Scleractinia.     

The Insulin Resistance—Dyslipidemic Syndrome of Visceral Obesity: Effect on Patients' Risk

Coronary heart disease (CHD) and type 2 diabetes mellitus represent two highly prevalent conditions in affluent societies. Although a dyslipidemic state is frequently found in type 2 patients with obesity, studies have shown that the high triglyceride, low high-density lipoprotein (HDL) cholesterol dyslipidemia is also found in nondiabetic patients with insulin resistance. Studies that have used imaging techniques to assess the regional distribution of body fat have shown that an excess of visceral adipose tissue, that is, a high accumulation of fat in the abdominal cavity, was associated with a cluster of metabolic disturbances such as insulin resistance, hyperinsulinemia, glucose intolerance, hypertriglyceridemia, elevated apolipoprotein B (apoB) concentrations, small, dense low-density lipoprotein (LDL) particles, as well as low HDL cholesterol levels. Prospective studies such as the Quebec Cardiovascular Study have shown that this cluster of metabolic abnormalities commonly found in patients with excess visceral adipose tissue substantially increases the risk of CHD. The high prevalence of visceral obesity in sedentary adult men and postmenopausal women is such that it may represent the most prevalent cause of atherogenic dyslipidemic states associated with CHD in our population.     

Modelling the species richness distribution of French dung beetles (Coleoptera, Scarabaeidae) and delimiting the predictive capacity of different groups of explanatory variables

Aim To predict French Scarabaeidae dung beetle species richness distribution, and to determine the possible underlying causal factors. Location The entire French territory has been studied by dividing it into 301 grid cells of 0.72 × 0.36 degrees. Method Species richness distribution was predicted using generalized linear models to relate the number of species with spatial, topographic and climate variables in grid squares previously identified as well sampled (n = 66). The predictive function includes the curvilinear relationship between variables, interaction terms and the significant third‐degree polynomial terms of latitude and longitude. The final model was validated by a jack‐knife procedure. The underlying causal factors were investigated by partial regression analysis, decomposing the variation in species richness among spatial, topographic and climate type variables. Results The final model accounts for 86.2% of total deviance, with a mean jack‐knife predictive error of 17.7%. The species richness map obtained highlights the Mediterranean as the region richest in species, and the less well‐explored south‐western region as also being species‐rich. The largest fraction of variability (38%) in the number of species is accounted for by the combined effect of the three groups of explanatory variables. The spatially structured climate component explains 21% of variation, while the pure climate and pure spatial components explain 14% and 11%, respectively. The effect of topography was negligible. Conclusions Delimiting the adequately inventoried areas and elaborating forecasting models using simple environmental variables can rapidly produce an estimate of the species richness distribution. Scarabaeidae species richness distribution seems to be mainly influenced by temperature. Minimum mean temperature is the most influential variable on a local scale, while maximum and mean temperature are the most important spatially structured variables. We suggest that species richness variation is mainly conditioned by the failure of many species to go beyond determined temperature range limits.