Somatic mutations in the neurofibromatosis type 2 gene in sporadic meningiomas

Meningiomas are benign tumors of the central nervous system. Although usually sporadic, they can occur in patients affected by the autosomal dominant syndrome, neurofibromatosis type 2 (NF2). The NF2 gene has recently been isolated from chromosome 22. The presence of germline mutations in NF2 patients and the loss of heterozygosity (LOH) on 22q in NF2 tumors support the hypothesis that the NF2 gene acts as a tumor suppressor. Cytogenetic and LOH studies have suggested that the gene responsible for the development of meningiomas is located in the region of 22q in which the NF2 gene maps. The meningioma gene could therefore be the NF2 gene itself. Recently, somatic mutations of the NF2 gene have been identified in sporadic meningiomas, thus supporting the hypothesis that the NF2 gene is also important in meningioma pathogenesis. In this study, we analyzed sixty-one sporadic meningiomas for LOH of 22q and for mutations in the NF2 gene. LOH was detected in 36 of the 60 informative tumors. Single-strand conformational polymorphism analysis was used to identify nine mutations in five of the eight exons of the NF2 gene studied. The nine tumors with an altered NF2 gene also showed LOH for 22q markers. These results further support the hypothesis that mutations in the NF2 gene are a critical pathogenetic event in at least some meningiomas.     

Ecogeographical variation in skull morphometry of howler monkeys (Primates: Atelidae)

Our aim is to identify ecomorphological adaptations in the skull shape of the South American howler monkeys (species of the genus Alouatta, Lacépède, 1799, Primates, Atelidae). Since Alouatta is relatively homogenous in feeding ecology, we expect skull shape variation to be relatively conservative across species. We used geometric morphometrics to quantify craniodental morphology in six species of Alouatta. Multivariate regression, two-block Partial Least Squares, and variation partitioning were used to test for the impact of taxonomy, sexual dimorphism, allometry, geography and climate on skull shape. We found morphological overlap among species and sexes, although some discrimination occurs between species living in seasonal environments as opposed to rain forest species. There was a negative latitudinal gradient in skull size across species, with size explaining 34% of total shape variance. Latitude and climate, though important, were secondary in explaining shape variance. Amazonian Alouatta are larger, have thinner molars, wide incisors, and proportionally larger neurocranium. Overall, the shape of southern species seem well adapted to cope with proportionally tougher food items, whereas Amazonian species seem better equipped to deal with a diet richer in fruits, as confirmed by independent field observations. The small size of Alouatta in the South is possibly linked to the effect of competition with the larger folivorous atelid Brachyteles.     

Altered Ion Channel Formation by the Parkinson's-Disease-Linked E46K Mutant of α-Synuclein Is Corrected by GM3 but Not by GM1 Gangliosides

α-Synuclein (α-syn) is an amyloidogenic protein that plays a key role in the pathogenesis of Parkinson's disease (PD). The ability of α-syn oligomers to form ionic channels is postulated as a channelopathy mechanism in human brain. Here we identified a ganglioside-binding domain in α-syn (fragment 34-50), which includes the mutation site 46 linked to a familial form of PD (E46K). We show that this fragment is structurally related to the common glycosphingolipid-binding domain (GBD) shared by various microbial and amyloid proteins, including Alzheimer's β-amyloid peptide. α-Syn GBD interacts with several glycosphingolipids but has a marked preference for GM3, a minor brain ganglioside whose expression increases with aging. The α-syn mutant E46K has a stronger affinity for GM3 than the wild-type protein, and the interaction is inhibited by 3′-sialyllactose (the glycone part of GM3). Alanine substitutions of Lys34 and Tyr39 in synthetic GBD peptides resulted in limited interaction with GM3, demonstrating the critical role of these residues in GM3 recognition. When incubated with reconstituted phosphatidylcholine bilayers, the E46K protein formed channels that are five times less conductive than those formed by wild-type α-syn, exhibit a higher selectivity for cations, and present an asymmetrical response to voltage and nonstop single-channel activity. This E46K-associated channelopathy was no longer observed when GM3 was present in phosphatidylcholine bilayers. This corrective effect was highly specific for GM3, since it was not obtained with the major brain ganglioside GM1 but was still detected in bilayer membranes containing both GM3 and GM1. Moreover, synthetic GBD peptides prevented the interaction of α-syn proteins with GM3, thus abolishing the regulatory effects of GM3 on α-syn-mediated channel formation. Overall, these data show that GM3 can specifically regulate α-syn-induced channel formation and raise the intriguing possibility that this minor brain ganglioside could play a key protective role in the pathogenesis of PD.     

Bindarit Inhibits Human Coronary Artery Smooth Muscle Cell Proliferation,Migration and Phenotypic Switching

Bindarit, a selective inhibitor of monocyte chemotactic proteins (MCPs) synthesis, reduces neointimal formation in animal models of vascular injury and recently has been shown to inhibit in-stent late loss in a placebo-controlled phase II clinical trial. However, the mechanisms underlying the efficacy of bindarit in controlling neointimal formation/restenosis have not been fully elucidated. Therefore, we investigated the effect of bindarit on human coronary smooth muscle cells activation, drawing attention to the phenotypic modulation process, focusing on contractile proteins expression as well as proliferation and migration. The expression of contractile proteins was evaluated by western blot analysis on cultured human coronary smooth muscle cells stimulated with TNF-α (30 ng/mL) or fetal bovine serum (5%). Bindarit (100–300 µM) reduced the embryonic form of smooth muscle myosin heavy chain while increased smooth muscle α-actin and calponin in both TNF-α- and fetal bovine serum-stimulated cells. These effects were associated with the inhibition of human coronary smooth muscle cell proliferation/migration and both MCP-1 and MCP-3 production. The effect of bindarit on smooth muscle cells phenotypic switching was confirmed in vivo in the rat balloon angioplasty model. Bindarit (200 mg/Kg/day) significantly reduced the expression of the embryonic form of smooth muscle myosin heavy chain, and increased smooth muscle α-actin and calponin in the rat carodid arteries subjected to endothelial denudation. Our results demonstrate that bindarit induces the differentiated state of human coronary smooth muscle cells, suggesting a novel underlying mechanisms by which this drug inhibits neointimal formation.     

Tonotopic gradients of Eph family proteins in the chick nucleus laminaris during synaptogenesis

Topographically precise projections are established early in neural development. One such topographically organized network is the auditory brainstem. In the chick, the auditory nerve transmits auditory information from the cochlea to nucleus magnocellularis (NM). NM in turn innervates nucleus laminaris (NL) bilaterally. These projections preserve the tonotopy established at the level of the cochlea. We have begun to examine the expression of Eph family proteins during the formation of these connections. Optical density measurements were used to describe gradients of Eph proteins along the tonotopic axis of NL in the neuropil, the somata, and the NM axons innervating NL at embryonic day 10, when synaptic connections from NM to NL are established. At E10-11, NL dorsal neuropil expresses EphA4 at a higher concentration in regions encoding high frequency sounds, decreasing in concentration monotonically toward the low frequency (caudolateral) end. In the somata, both EphA4 and ephrin-B2 are concentrated at the high frequency end of the nucleus. These tonotopic gradients disappear between E13 and E15, and expression of these molecules is completely downregulated by hatching. The E10-11 patterns run counter to an apparent gradient in dendrite density, as indicated by microtubule associated protein 2 (MAP2) immunolabeling. Finally, ephrin-B2 is also expressed in a gradient in tissue ventral to the NL neuropil. Our findings thus suggest a possible conserved mechanism for establishing topographic projections in diverse sensory systems. These results of this study provide a basis for the functional examination of the role of Eph proteins in the formation of tonotopic maps in the brainstem.     

Comparative IR study of solid hydrate decavanadates and polyvanadates in acidic aqueous solution

An attempt has been made to compare i.r. spectra of polyvanadate solutions with those of solid polyvanadates, in order to solve the problem if aqueous solution decavanadate species have the same structure as reported in solid hydrate decavanadates, and if hexavanadate species are coexisting with them.The i.r. spectra directly obtained from water solutions were unreliable; so, solution species have been extracted into a low absorbing organic phase. A previous control showed that no modifications of existing species were occurring for the phase transfer. In this way, evidence resulted for a complete identity between aqueous solution and solid decavanadate structure, and for a lack of hexavanadate species, at least within the sensitivity limits of the i.r. technique.These findings are in agreement with a recent Raman investigation, but appear in contrast with NMR and complexation data. A new interpretation of NMR data is suggested, leading to the removal of disagreement.     

Synthesis of photoaffinity label analogues of α-tocopherol

Photoaffinity analogues of α-tocopherol have been synthesized that incoroporate the photosensitive 4-azido-2,3,5,6-tetrafluorobenzyloxy group at the terminus of unbranched analogues of the naturally occurring phytyl side chain. An intermediate from these syntheses has also been used to generate a supported lignnd for bioaffinity chromatography of α-tocopherol binding proteins.     

How a Small Double-Stranded Trick Can Mislead Sanger Sequencing

Notwithstanding the arrival of “third-generation sequencing,” Sanger sequencing, developed in 1980, is still the most accurate and used method for sequencing, although on a smaller scale. It is a powerful resource for studying sequences and discovering polymorphisms and genes, as well as regulatory elements. There has already been described a wide range of possible problems with this very sensitive and accurate technology. Here, we show that a specific event, related to genomes rich in repetitive sequences, can mislead operators working with Sanger sequencing.