Human monoamine oxidase A and B genes map to xp11.23 and are deleted in a patient with norrie disease

Monoamine oxidase A and B (MAO A and B) are the central enzymes that catalyze oxidative deamination of biogenic amines throughout the body. The regional locations of genes encoding MAO A and B on the X chromosome were determined by using full-length cDNA clones for human MAO A and B, respectively. Using somatic cell hybrids, in situ hybridization, and field-inversion gel electrophoresis as well as deletion mapping in a patient with Norrie disease, we concluded that these two genes are close to each other and to the DXS7 locus (Xp11.3).     

Deletion of a malaria invasion gene reduces death and anemia, in model hosts

Malaria parasites induce complex cellular and clinical phenotypes, including anemia, cerebral malaria and death in a wide range of mammalian hosts. Host genes and parasite 'toxins' have been implicated in malarial disease, but the contribution of parasite genes remains to be fully defined. Here we assess disease in BALB/c mice and Wistar rats infected by the rodent malaria parasite Plasmodium berghei with a gene knock out for merozoite surface protein (MSP) 7. MSP7 is not essential for infection but in P. falciparum, it enhances erythrocyte invasion by 20%. In vivo, as compared to wild type, the P. berghei Δmsp7 mutant is associated with an abrogation of death and a decrease from 3% to 2% in peak, circulating parasitemia. The Δmsp7 mutant is also associated with less anemia and modest increase in the size of follicles in the spleen. Together these data show that deletion of a single parasite invasion ligand modulates blood stage disease, as measured by death and anemia. This work is the first to assess the contribution of a gene present in all plasmodial species in severe disease.     

Native ultrastructure of the red cell cytoskeleton by cryo-electron tomography

Erythrocytes possess a spectrin-based cytoskeleton that provides elasticity and mechanical stability necessary to survive the shear forces within the microvasculature. The architecture of this membrane skeleton and the nature of its intermolecular contacts determine the mechanical properties of the skeleton and confer the characteristic biconcave shape of red cells. We have used cryo-electron tomography to evaluate the three-dimensional topology in intact, unexpanded membrane skeletons from mouse erythrocytes frozen in physiological buffer. The tomograms reveal a complex network of spectrin filaments converging at actin-based nodes and a gradual decrease in both the density and the thickness of the network from the center to the edge of the cell. The average contour length of spectrin filaments connecting junctional complexes is 46 ± 15 nm, indicating that the spectrin heterotetramer in the native membrane skeleton is a fraction of its fully extended length (∼190 nm). Higher-order oligomers of spectrin were prevalent, with hexamers and octamers seen between virtually every junctional complex in the network. Based on comparisons with expanded skeletons, we propose that the oligomeric state of spectrin is in a dynamic equilibrium that facilitates remodeling of the network as the cell changes shape in response to shear stress.     

Inter-subunit interactions in erythroid and non-erythroid spectrins

Spectrins comprise α- and β-subunits made up predominantly of a series of homologous repeating units of about 106 amino acids; the α- and β-chains form antiparallel dimers by lateral association, and tetramers through head-to-head contacts between the dimers. Here we consider the first of these interactions. (1) We confirm earlier observations, showing that the first two paired repeats (βIR1 with αIR21, and βIR2 with αRI20) at one end of the erythroid spectrin (αIβI) dimer are necessary and sufficient to unite the chains; (2) we resolve a conflict in published reports by showing that the strength of the interaction is considerably increased on adding the adjoining pair of repeats (βIR3-αIR19); (3) in brain (αIIβII) spectrin the first two pairs of repeats are similarly essential and sufficient for heterodimer formation; (4) this interaction is ~60-fold stronger than that in the erythroid counterpart, but no enhancement can be detected on addition of three further pairs of repeats; (5) formation of a tight αIβI dimer probably depends on structural coupling of the first two repeats in each chain; (6) an analysis of the sequences of the strongly interacting repeats, βIR1, βIIR1, αIR21 and αIIR20 and repeats in α-actinin, which also interact very strongly in forming an antiparallel dimer, affords a possible explanation for the different properties of the two spectrin isoforms in respect of the stability of the inter-chain interactions, and also suggests the evolutionary path by which the erythroid and non-erythroid sequences diverged.     

Convergent Antibody Signatures in Human Dengue

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Two Seven-Transmembrane Domain MILDEW RESISTANCE LOCUS O Proteins Cofunction in Arabidopsis Root Thigmomorphogenesis

Directional root expansion is governed by nutrient gradients, positive gravitropism and hydrotropism, negative phototropism and thigmotropism, as well as endogenous oscillations in the growth trajectory (circumnutation). Null mutations in phylogenetically related Arabidopsis thaliana genes MILDEW RESISTANCE LOCUS O 4 (MLO4) and MLO11, encoding heptahelical, plasma membrane–localized proteins predominantly expressed in the root tip, result in aberrant root thigmomorphogenesis. mlo4 and mlo11 mutant plants show anisotropic, chiral root expansion manifesting as tightly curled root patterns upon contact with solid surfaces. The defect in mlo4 and mlo11 mutants is nonadditive and dependent on light and nutrients. Genetic epistasis experiments demonstrate that the mutant phenotype is independently modulated by the Gβ subunit of the heterotrimeric G-protein complex. Analysis of expressed chimeric MLO4/MLO2 proteins revealed that the C-terminal domain of MLO4 is necessary but not sufficient for MLO4 action in root thigmomorphogenesis. The expression of the auxin efflux carrier fusion, PIN1-green fluorescent protein, the pattern of auxin-induced gene expression, and acropetal as well as basipetal auxin transport are altered at the root tip of mlo4 mutant seedlings. Moreover, addition of auxin transport inhibitors or the loss of EIR1/AGR1/PIN2 function abolishes root curling of mlo4, mlo11, and wild-type seedlings. These results demonstrate that the exaggerated root curling phenotypes of the mlo4 and mlo11 mutants depend on auxin gradients and suggest that MLO4 and MLO11 cofunction as modulators of touch-induced root tropism.     

Differential sialylation regulates the apoptotic activity of glycodelin A

Glycodelin A (GdA), a dimeric lipocalin, expressed by the uterine endometrium, is an immunomodulatory agent and induces apoptosis in T-cells. In this study we demonstrate that two populations of GdA with subtle differences in their net ionic charge are present in the amniotic fluid and that, apoptotic activity is exhibited only by the population with more sialic acid residues. Significantly, removal of sialic acid residues from the active populations of GdA abrogates the activity of the molecule, suggesting that the extent of sialylation might be a factor regulating the activity of GdA.