Infantile convulsions with paroxysmal dyskinesia (ICCA syndrome) and copy number variation at human chromosome 16p11

Background

Benign infantile convulsions and paroxysmal dyskinesia are episodic cerebral disorders that can share common genetic bases. They can be co-inherited as one single autosomal dominant trait (ICCA syndrome); the disease ICCA gene maps at chromosome 16p12-q12. Despite intensive and conventional mutation screening, the ICCA gene remains unknown to date. The critical area displays highly complicated genomic architecture and is the site of deletions and duplications associated with various diseases. The possibility that the ICCA syndrome is related to the existence of large-scale genomic alterations was addressed in the present study.

Methodology/Principal Findings

A combination of whole genome and dedicated oligonucleotide array comparative genomic hybridization coupled with quantitative polymerase chain reaction was used. Low copy number of a region corresponding to a genomic variant (Variation_7105) located at 16p11 nearby the centromere was detected with statistical significance at much higher frequency in patients from ICCA families than in ethnically matched controls. The genomic variant showed no apparent difference in size and copy number between patients and controls, making it very unlikely that the genomic alteration detected here is ICCA-specific. Furthermore, no other genomic alteration that would directly cause the ICCA syndrome in those nine families was detected in the ICCA critical area.

Conclusions/Significance

Our data excluded that inherited genomic deletion or duplication events directly cause the ICCA syndrome; rather, they help narrowing down the critical ICCA region dramatically and indicate that the disease ICCA genetic defect lies very close to or within Variation_7105 and hence should now be searched in the corresponding genomic area and its surrounding regions.     

Erratum

Neurotransmitter receptor trafficking and the regulation of synaptic strength. Traffic 2001:2(7):437–448.     

Characterization of the Rac guanine nucleotide exchange factor P-Rex1 in platelets

Background

Blood platelets undergo a carefully regulated change in shape to serve as the primary mediators of hemostasis and thrombosis. These processes manifest through platelet spreading and aggregation and are dependent on platelet actin cytoskeletal changes orchestrated by the Rho GTPase family member Rac1. To elucidate how Rac1 is regulated in platelets, we captured Rac1-interacting proteins from platelets and identified Rac1-associated proteins by mass spectrometry.

Findings

Here, we demonstrate that Rac1 captures the Rac guanine nucleotide exchange factor P-Rex1 from platelet lysates. Western blotting experiments confirmed that P-Rex1 is expressed in platelets and associated with Rac1. To investigate the functional role of platelet P-Rex1, platelets from P-Rex1 ^-/- -deficient mice were treated with platelet agonists or exposed to platelet activating surfaces of fibrinogen, collagen and thrombin. Platelets from P-Rex1 ^-/- mice responded to platelet agonists and activating surfaces similarly to wild type platelets.

Conclusions

These findings suggest that P-Rex1 is not required for Rac1-mediated platelet activation and that the GEF activities of P-Rex1 may be more specific to GPCR chemokine receptor mediated processes in immune cells and tumor cells.     

Hybrid metabolic flux analysis: combining stoichiometric and statistical constraints to model the formation of complex recombinant products

Background  

Stoichiometric models constitute the basic framework for fluxome quantification in the realm of metabolic engineering. A recurrent bottleneck, however, is the establishment of consistent stoichiometric models for the synthesis of recombinant proteins or viruses. Although optimization algorithms for in silico metabolic redesign have been developed in the context of genome-scale stoichiometric models for small molecule production, still rudimentary knowledge of how different cellular levels are regulated and phenotypically expressed prevents their full applicability for complex product optimization.     

ALK-activating homologous mutations in LTK induce cellular transformation

Leukocyte tyrosine kinase (LTK) is a receptor tyrosine kinase reported to be overexpressed in human leukemia. Though much regarding the function of LTK remains unknown, it shares a high degree of similarity with anaplastic lymphoma kinase (ALK), which is found mutated in human cancer. In order to determine if LTK has transforming potential, we created two LTK mutants, F568L and R669Q, that correspond to two well-characterized activating mutations of ALK (F1174L and R1275Q). LTK-F568L, but not wildtype LTK or LTK-R669Q, transformed hematopoietic cells to cytokine independence. LTK-F568L exhibited a stronger ability to induce loss of contact inhibition and anchorage-independent growth of epithelial cells compared to LTK-R669Q, while wildtype LTK was non-transforming in the same cells. Likewise, LTK-F568L induced greater neurite outgrowth of PC12 cells than R669Q, while wildtype LTK could not. Correlating with transforming activity, LTK-F568L displayed significantly enhanced tyrosine phosphorylation compared to wildtype LTK and LTK-R668Q and induced activation of various signaling proteins including Shc, ERK and the JAK/STAT pathway. Expression of wildtype LTK or LTK-R669Q generally led to weaker activation of signaling proteins than expression of LTK-F568L, or no activation at all. Thus, mutating LTK at residue F568, and to a lesser extent at R669, activates the receptor tyrosine kinase, inducing cell signaling that results in transforming properties. These studies suggest that aberrant activation of LTK may contribute to neoplastic cell growth.     

Ready-to-use therapeutic food for catch-up growth in children after an episode of Plasmodium falciparum malaria: an open randomised controlled trial

Background

Catch-up growth after an infection is essential for children to maintain good nutritional status. To prevent malnutrition, WHO recommends that children are given one additional healthy meal per day during the 2 weeks after onset of illness. We investigated to what extent ready-to-use therapeutic food (RUTF) promotes catch-up growth in children after an acute, uncomplicated episode of Plasmodium falciparum malaria.

Methods

We did an open randomised trial of children aged 6–59 months with confirmed malaria who attended a Médecins Sans Frontières-supported outpatient clinic in Katanga Province, Democratic Republic of Congo. All children received a clinical examination and malaria treatment. Patients were then randomly assigned to either an RUTF group, who received daily supplemental RUTF (a high-protein peanut-based paste) for 14 days, or to a control group, who received no supplemental food. Children were weighed at baseline and on days 14 and 28. The primary outcome was mean weight change after 14 days'' RUTF. Analysis was by intention-to-treat.

Results

93 children received RUTF and 87 received no food supplementation. At day 14, the RUTF group had a mean weight gain of 353 g compared with 189 g in the control group (difference 164 [95%CI 52–277], p = 0.005). However, at day 28 there was no statistically significant difference between the groups (539 g versus 414 g, respectively [p = 0.053]). Similarly, rate of weight gain per kg bodyweight per day was significantly higher at day 14 in the RUTF group (2.4 g/kg per day versus 1.3 g/kg per day, p = 0.005) but at day 28 was 1.9 g/kg per day in the RUTF group versus 1.5 g/kg per day in the control group (p = 0.076).

Conclusions

Children receiving RUTF for 14 days after effective treatment of an uncomplicated malaria episode had a faster weight gain than children not given supplementation, reducing the period that children were at risk of malnutrition.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00819858","term_id":"NCT00819858"}}NCT00819858     

Quantitative radiochromatographic analysis of the major groups of carbohydrates in cultured animal cells.

Procedures are described for selective quantitation of the monosaccharide content of glycogen, chondroitin sulfates, hyaluronic acid, glycoproteins, glycolipids, N-acetylneuraminic acid, and the phosphorylated carbohydrate pools in cultured animal cells. Monosaccharides are released from each type of carbohydrate by selective hydrolysis with enzymes and/or acid and are analyzed by radiochromatographic procedures which give reliable quantitative data with only a few nanomoles of each monosaccharide. Analyses of the entire spectrum of carbohydrates can be carried out using 7–8 mg of animal cell protein.