Molecular screening of ADAMTSL2 gene in 33 patients reveals the genetic heterogeneity of geleophysic dysplasia.

Background Geleophysic dysplasia (GD, OMIM 231050) is an autosomal recessive disorder characterised by short stature, small hands and feet, stiff joints, and thick skin. Patients often present with a progressive cardiac valvular disease which can lead to an early death. In a previous study including six GD families, we have mapped the disease gene on chromosome 9q34.2 and identified mutations in the A Disintegrin And Metalloproteinase with Thrombospondin repeats-like 2 gene (ADAMTSL2). Methods Following this study, we have collected the samples of 30 additional GD families, including 33 patients and identified ADAMTSL2 mutations in 14/33 patients, comprising 13 novel mutations. The absence of mutation in 19 patients prompted us to compare the two groups of GD patients, namely group 1, patients with ADAMTSL2 mutations (n=20, also including the 6 patients from our previous study), and group 2, patients without ADAMTSL2 mutations (n=19). Results The main discriminating features were facial dysmorphism and tip-toe walking, which were almost constantly observed in group 1. No differences were found concerning heart involvement, skin thickness, recurrent respiratory and ear infections, bronchopulmonary insufficiency, laryngo-tracheal stenosis, deafness, and radiographic features. Conclusions It is concluded that GD is a genetically heterogeneous condition. Ongoing studies will hopefully lead to the identification of another disease gene.

MIBG scintigraphy for the diagnosis and follow-up of children with neuroblastoma.

Neuroblastoma (NBL) is the commonest extra-cranial solid tumor in children and the leading cause of cancer related deaths in childhood between the age of 1 to 4 years. NBL may behave in very different ways, from the less aggressive stage 4S NBL or congenital forms that may resolve without treatment in up to 90% of the children, to the high-risk disseminated stage 4 disease in older children with a cure rate of 35 to 40%. Initial staging is crucial for effective management and radiolabeled metaiodobenzylguanidine (MIBG) with iodine-123 is a powerful tool with a sensitivity around 90% and a specificity close to 100% for the diagnosis of NBL. MIBG scintigraphy is used routinely and is mandatory in most investigational clinical trials both for the initial staging of the disease, the evaluation of the response to treatment, as well as for the detection of recurrence during follow-up. With respect to outcome of children presenting disseminated stage 4 NBL, the role of post-therapeutic [(123)I]MIBG scan has been investigated by several groups but so far there is no consensus whereas a complete or very good partial response as assessed by MIBG may be of prognostic value. NBL needs a multimodality approach at diagnosis and during follow-up and MIBG scintigraphy keeps its pivotal role, in particular with respect to bone marrow involvement and/or cortical bone metastases.

Proteinaceous infectious behavior in non-pathogenic proteins is controlled by molecular chaperones.

External stresses or mutations may cause labile proteins to lose their distinct native conformations and seek alternatively stable aggregated forms. Molecular chaperones that specifically act on protein aggregates were used here as a tool to address the biochemical nature of stable homo- and hetero-aggregates from non-pathogenic proteins formed by heat-stress. Confirmed by sedimentation and activity measurements, chaperones demonstrated that a single polypeptide chain can form different species of aggregates, depending on the denaturing conditions. Indicative of a cascade reaction, sub-stoichiometric amounts of one fast-aggregating protein strongly accelerated the conversion of another soluble, slow-aggregating protein into insoluble, chaperone-resistant aggregates. Chaperones strongly inhibited seed-induced protein aggregation, suggesting that they can prevent and cure proteinaceous infectious behavior in homo- and hetero-aggregates from common and disease-associated proteins in the cell.

Neuropathological, clinical and molecular pathology in female fragile X premutation carriers with and without FXTAS.

Fragile X-associated tremor/ataxia syndrome (FXTAS) is an adult-onset neurodegenerative disorder associated with premutation alleles of the fragile X mental retardation 1 (FMR1) gene. Approximately 40% of older male premutation carriers, and a smaller proportion of females, are affected by FXTAS; due to the lower penetrance the characterization of the disorder in females is much less detailed. Core clinical features of FXTAS include intention tremor, cerebellar gait ataxia and frequently parkinsonism, autonomic dysfunction and cognitive deficits progressing to dementia in up to 50% of males. In this study, we report the clinical, molecular and neuropathological findings of eight female premutation carriers. Significantly, four of these women had dementia; of the four, three had FXTAS plus dementia. Post-mortem examination showed the presence of intranuclear inclusions in all eight cases, which included one asymptomatic premutation carrier who died from cancer. Among the four subjects with dementia, three had sufficient number of cortical amyloid plaques and neurofibrillary tangles to make Alzheimer's disease a highly likely cause of dementia and a fourth case had dementia with cortical Lewy bodies. Dementia appears to be more common than originally reported in females with FXTAS. Although further studies are required, our observation suggests that in a portion of FXTAS cases there is Alzheimer pathology and perhaps a synergistic effect on the progression of the disease may occur.

Making sense of AMPA receptor trafficking by modeling molecular mechanisms of synaptic plasticity.

Synaptic plasticity involves a complex molecular machinery with various protein interactions but it is not yet clear how its components give rise to the different aspects of synaptic plasticity. Here we ask whether it is possible to mathematically model synaptic plasticity by making use of known substances only. We present a model of a multistable biochemical reaction system and use it to simulate the plasticity of synaptic transmission in long-term potentiation (LTP) or long-term depression (LTD) after repeated excitation of the synapse. According to our model, we can distinguish between two phases: first, a "viscosity" phase after the first excitation, the effects of which like the activation of NMDA receptors and CaMKII fade out in the absence of further excitations. Second, a "plasticity" phase actuated by an identical subsequent excitation that follows after a short time interval and causes the temporarily altered concentrations of AMPA subunits in the postsynaptic membrane to be stabilized. We show that positive feedback is the crucial element in the core chemical reaction, i.e. the activation of the short-tail AMPA subunit by NEM-sensitive factor, which allows generating multiple stable equilibria. Three stable equilibria are related to LTP, LTD and a third unfixed state called ACTIVE. Our mathematical approach shows that modeling synaptic multistability is possible by making use of known substances like NMDA and AMPA receptors, NEM-sensitive factor, glutamate, CaMKII and brain-derived neurotrophic factor. Furthermore, we could show that the heteromeric combination of short- and long-tail AMPA receptor subunits fulfills the function of a memory tag.

Characterization of the Morphological and Molecular Changes Associated with Diabetic Peripheral Neuropathy in Type 2 Diabetes

More than 246 million individuals worldwide are affected by diabetes mellitus (DM) and this number is rapidly increasing (http://www.eatlas. idf.org). 90% of all diabetic patients have type 2 DM, which is characterized by insulin resistance and b-cell dysfunction. Even though diabetic peripheral neuropathy (DPN) is the major chronic complication of DM its underlying pathophysiological mechanisms still remain unknown. To get more insight into the DPN associated with type 2 DM, we characterized the rodent model of this form of diabetes, the db/db mice. The progression of pathological changes in db/db mice mimics the ones observed in humans: increase of the body weight, insulin insensitivity, elevated blood glucose level and reduction in nerve conduction velocity (NCV). Decreased NCV, present in many peripheral neuropathies, is usually associated with demyelination of peripheral nerves. However, our detailed analysis of the sciatic nerves of db/db mice exposed for 4 months to hyperglycemia, failed to reveal any signs of demyelination in spite of significantly reduced NCV in these animals. We therefore currently focus our analysis on the structure of Nodes of Ranvier, regions of intense axo-glial interactions, which also play a crucial role in rapid saltatory impulse conduction. In addition we are also evaluating molecular changes in somas of sensory neurons projecting through sciatic nerve, which are localized in the dorsal root ganglia. We hope that the combination of these approaches will shed light on molecular alterations leading to DPN as a consequence of type 2 DM.

IROme, a New High-Throughput Molecular Tool for the Diagnosis of Inherited Retinal Dystrophies-A Price Comparison with Sanger Sequencing.

The molecular diagnosis of retinal dystrophies (RD) is difficult because of genetic and clinical heterogeneity. Previously, the molecular screening of genes was done one by one, sometimes in a scheme based on the frequency of sequence variants and the number of exons/length of the candidate genes. Payment for these procedures was complicated and the sequential billing of several genes created endless paperwork. We therefore evaluated the costs of generating and sequencing a hybridization-based DNA library enriched for the 64 most frequently mutated genes in RD, called IROme, and compared them to the costs of amplifying and sequencing these genes by the Sanger method. The production cost generated by the high-throughput (HT) sequencing of IROme was established at CHF 2,875.75 per case. Sanger sequencing of the same exons cost CHF 69,399.02. Turnaround time of the analysis was 3 days for IROme. For Sanger sequencing, it could only be estimated, as we never sequenced all 64 genes in one single patient. Sale cost for IROme calculated on the basis of the sale cost of one exon by Sanger sequencing is CHF 8,445.88, which corresponds to the sale price of 40 exons. In conclusion, IROme is cheaper and faster than Sanger sequencing and therefore represents a sound approach for the diagnosis of RD, both scientifically and economically. As a drop in the costs of HT sequencing is anticipated, target resequencing might become the new gold standard in the molecular diagnosis of RD.

The molecular basis of social behavior: models, methods and advances.

Elucidating the molecular and neural basis of complex social behaviors such as communal living, division of labor and warfare requires model organisms that exhibit these multi-faceted behavioral phenotypes. Social insects, such as ants, bees, wasps and termites, are attractive models to address this problem, with rich ecological and ethological foundations. However, their atypical systems of reproduction have hindered application of classical genetic approaches. In this review, we discuss how recent advances in social insect genomics, transcriptomics, and functional manipulations have enhanced our ability to observe and perturb gene expression, physiology and behavior in these species. Such developments begin to provide an integrated view of the molecular and cellular underpinnings of complex social behavior.