Polymorphism in a ferritin H gene from chromosome 6p

Summary This paper addresses the question of whether abnormalities in ferritin expression in the iron storage disease hemochromatosis (HC) involve major deletions or alterations in regions containing the two ferritin H genes that lie near the disease locus on chromosome 6p. We present evidence from analyses of Southern blots that neither gene is deleted in hemochromatosis. We also describe a polymorphism in one of the genes that we have previously shown to be a processed pseudogene. This polymorphism does not correlate with the presence of HC. The PIC value for this polymorphism was calculated as 0.49.     

Ferritin H gene polymorphism in idiopathic hemochromatosis

Summary We have analysed karyotypes and DNA from three patients with aniridia (congenital absence of irises) and Wilms' tumour. All three had constitutional deletions from the short arm of chromosome 11. The minimum region of overlap of the deletion involves a small region of band 11p13 presumed to contain the genetic loci responsible for both phenotypic abnormalities. Using cells from these patients, somatic cell hybrids with transformed mouse cells have been prepared. Individual subclones retaining either the deletion-11 chromosome or the normal chromosome 11, in addition to a variety of other human chromosomes, have been identified. The relative position of these breakpoints have been determined and the panel of hybrids has been used to map randomly-isolated 11p13 DNA sequences. The characterisation of these deletions has provided a useful panel of hybrids for random mapping strategies designed to identify the Wilms' and aniridia genes.     

Adsorption, lubrication, and wear of lubricin on model surfaces: polymer brush-like behavior of a glycoprotein

Using a surface force apparatus, we have measured the normal and friction forces between layers of the human glycoprotein lubricin, the major boundary lubricant in articular joints, adsorbed from buffered saline solution on various hydrophilic and hydrophobic surfaces: i), negatively charged mica, ii), positively charged poly-lysine and aminothiol, and iii), hydrophobic alkanethiol monolayers. On all these surfaces lubricin forms dense adsorbed layers of thickness 60–100 nm. The normal force between two surfaces is always repulsive and resembles the steric entropic force measured between layers of end-grafted polymer brushes. This is the microscopic mechanism behind the antiadhesive properties showed by lubricin in clinical tests. For pressures up to ~6 atm, lubricin lubricates hydrophilic surfaces, in particular negatively charged mica (friction coefficient μ = 0.02–0.04), much better than hydrophobic surfaces (μ > 0.3). At higher pressures, the friction coefficient is higher (μ > 0.2) for all surfaces considered and the lubricin layers rearrange under shear. However, the glycoprotein still protects the underlying substrate from damage up to much higher pressures. These results support recent suggestions that boundary lubrication and wear protection in articular joints are due to the presence of a biological polyelectrolyte on the cartilage surfaces.     

Preparation of shell cross-linked nano-objects from hybrid-peptide block copolymers

Supramolecular structures formed by self-assembly of diblock copolymers in solution are stable over restricted environmental conditions: concentration, temperature, pH, or ion strength among others. To enlarge their domain of application, it appears necessary to develop stabilization strategies. We report here different strategies to stabilize the shell of micelles formed by self-assembly of amphiphilic polydiene-b-polypeptide diblock copolymers. For this purpose, covalent bonds can be formed between either amine or carboxylic acid groups distributed along the soluble peptide block and a cross-linking agent that contains respectively aldehyde or amine functions. Shell stabilization affords systems with unique properties that combine three main advantages: shape persistence, control of the porosity, and stimuli-responsive behavior. The covalent capture of such macromolecular objects has been studied by light scattering, AFM, and conductimetry measurements.     

Effect of Ca2+ ions on the adhesion and mechanical properties of adsorbed layers of human osteopontin

Using an atomic force microscope and a surface force apparatus, we measured the surface coverage, adhesion, and mechanical properties of layers of osteopontin (OPN), a phosphoprotein of the human bones, adsorbed on mica. OPN is believed to connect mineralized collagen fibrils of the bone in a matrix that dissipates energy, reducing the risk of fractures. Atomic force microscopy normal force measurements showed large adhesion and energy dissipation upon retraction of the tip, which were due to the breaking of the many OPN-OPN and OPN-mica bonds formed during tip-sample contact. The dissipated energy increased in the presence of Ca²⁺ ions due to the formation of additional OPN-OPN and OPN-mica salt bridges between negative charges. The forces measured by surface force apparatus between two macroscopic mica surfaces were mainly repulsive and became hysteretic only in the presence of Ca²⁺: adsorbed layers underwent an irreversible compaction during compression due to the formation of long-lived calcium salt bridges. This provides an energy storage mechanism, which is complementary to energy dissipation and may be equally relevant to bone recovery after yield. The prevalence of one mechanism or the other appears to depend on the confinement geometry, adsorption protocol, and loading-unloading rates.     

The mutation ROR2W749X, linked to human BDB, is a recessive mutation in the mouse, causing brachydactyly, mediating patterning of joints and modeling recessive Robinow syndrome

Mutations in ROR2 result in a spectrum of genetic disorders in humans that are classified, depending on the nature of the mutation and the clinical phenotype, as either autosomal dominant brachydactyly type B (BDB, MIM 113000) or recessive Robinow syndrome (RRS, MIM 268310). In an attempt to model BDB in mice, the mutation W749X was engineered into the mouse Ror2 gene. In contrast to the human situation, mice heterozygous for Ror2(W749FLAG) are normal and do not develop brachydactyly, whereas homozygous mice exhibit features resembling RRS. Furthermore, both Ror2(W749FLAG/W749FLAG) and a previously engineered mutant, Ror2(TMlacZ/TMlacZ), lack the P2/P3 joint. Absence of Gdf5 expression at the corresponding interzone suggests that the defect is in specification of the joint. As this phenotype is absent in mice lacking the entire Ror2 gene, it appears that specification of the P2/P3 joint is affected by ROR2 activity. Finally, Ror2(W749FLAG/W749FLAG) mice survive to adulthood and exhibit phenotypes (altered body composition, reduced male fertility) not observed in Ror2 knockout mice, presumably due to the perinatal lethality of the latter. Therefore, Ror2(W749FLAG/W749FLAG) mice represent a postnatal model for RRS, provide insight into the mechanism of joint specification, and uncover novel roles of Ror2 in the mouse.