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This paper presents a novel approach for active chatter reduction using a motor spindle with integrated magnet actuators. Based on the results of previous studies the design of an active damped prototype is described. The system performance as well as the benefits and drawbacks of this solution are discussed. In order to eliminate the known drawbacks a novel actuator design is introduced. The novel approach integrates the actuator windings into the stator core. Next, strategies for electric and magnetic decoupling of the actuator and motor windings are presented. Subsequently the actuator design is discussed. The force generation and distribution of the damping actuator are calculated via analytical and finite elements analysis (FEA). With the novel approach the mechanical integration of the active damping actuators is simplified significantly. Additionally, the maximal attainable spindle power is increased up to 150% in relation to the previous solution.

Guiding systems for precision manufacturing machines have to fulfil high demands. Low compliance and the absence of friction is required to achieve a high production accuracy. This article presents a novel active guiding system based on the combination of ultrasonic levitation and magnetic actuators. Firstly, the combined actuator and its working principles are described. Subsequently, the concept for an active, frictionless and medium-free guiding system is outlined. In addition to the free degree of freedom (DOF) in guiding direction, the other 5 DOF are adjustable in order to improve the guides positioning accuracy. The experimental validation of the concept is conducted with a simplified prototype, acting as a 3 DOF adjustable planar guide. Finally, measured compliance frequency responses demonstrate the performance of this novel active guiding concept.

International audience; Defects in myosin VIIa, harmonin (a PDZ domain protein), cadherin 23, protocadherin 15 and sans (a putative scaffolding protein), underlie five forms of Usher syndrome type I (USH1). Mouse mutants for all these proteins exhibit disorganization of their hair bundle, which is the mechanotransduction receptive structure of the inner ear sensory cells, the cochlear and vestibular hair cells. We have previously demonstrated that harmonin interacts with cadherin 23 and myosin VIIa. Here we address the extent of interactions between the five known USH1 proteins. We establish the previously suggested sans-harmonin interaction and find that sans also binds to myosin VIIa. We show that sans can form homomeric structures and that harmonin b can interact with all harmonin isoforms. We reveal that harmonin also binds to protocadherin 15. Molecular characterization of these interactions indicates that through its binding to four of the five USH1 proteins, the first PDZ domain (PDZ1) of harmonin plays a central role in this network. We localize sans in the apical region of cochlear and vestibular hair cell bodies underneath the cuticular plate. In contrast to the other four known USH1 proteins, no sans labeling was detected within the stereocilia. We propose that via its binding to myosin VIIa and/or harmonin, sans controls the hair bundle cohesion and proper development by regulating the traffic of USH1 proteins en route to the stereocilia.

Deaf-blindness in three distinct genetic forms of Usher type I syndrome (USH1) is caused by defects in myosin VIIa, harmonin and cadherin 23. Despite being critical for hearing, the functions of these proteins in the inner ear remain elusive. Here we show that harmonin, a PDZ domain-containing protein, and cadherin 23 are both present in the growing stereocilia and that they bind to each other. Moreover, we demonstrate that harmonin b is an F-actin-bundling protein, which is thus likely to anchor cadherin 23 to the stereocilia microfilaments, thereby identifying a novel anchorage mode of the cadherins to the actin cytoskeleton. Moreover, harmonin b interacts directly with myosin VIIa, and is absent from the disorganized hair bundles of myosin VIIa mutant mice, suggesting that myosin VIIa conveys harmonin b along the actin core of the developing stereocilia. We propose that the shaping of the hair bundle relies on a functional unit composed of myosin VIIa, harmonin b and cadherin 23 that is essential to ensure the cohesion of the stereocilia.

Human Usher syndrome (USH) is the most common form of deaf-blindness and also the most frequent case of recessive retinitis pigmentosa. According to the degree of the clinical symptoms, three different types of the Usher syndrome are distinguished: USH1, USH2 and USH3 (Davenport and Omenn, 1977). USH is genetically heterogeneous with eleven chromosomal loci, which can be assigned to the three USH types (USH1A-G, USH2A-C, USH3A) (Petit, 2001). Out of these, USH1 is the most severe form, characterized by profound congenital deafness, constant vestibular dysfunction and prepubertal-onset retinitis pigmentosa. USH2 patients show a milder congenital deafness, a slightly later onset of retinitis pigmentosa and no vestibular dysfunction. The rarest Usher type 3 shows a late onset of retinitis pigmentosa and a progressing hearing loss. So far the different USH subtypes have been grouped into one disease basically on the same phenotype of the patients, although the clinical symptoms of the individual differ noticeably. The protein harmonin, responsible for USH1C, is of special interest, since it contains three PDZ domains, known for protein-protein interactions. We have gathered evidence that the different USH proteins are molecularly linked essentially via the scaffold protein harmonin. Harmonin interacts hereby not only with USH1 proteins, but also with USH2 proteins. Thus, this is the first evidence for a molecular linkage between USH1 and USH2, beyond the shared phenotype.

Usher syndrome (USH) is the most frequent cause of combined deaf-blindness in man. It is clinically and genetically heterogeneous and at least 12 chromosomal loci are assigned to three clinical USH types, namely USH1A-G, USH2A-C, USH3A (Davenport, S.L.H., Omenn, G.S., 1977. The heterogeneity of Usher syndrome. Vth Int. Conf. Birth Defects, Montreal; Petit, C., 2001. Usher syndrome: from genetics to pathogenesis. Annu. Rev. Genomics Hum. Genet. 2, 271-297). Mutations in USH type 1 genes cause the most severe form of USH. In USH1 patients, congenital deafness is combined with a pre-pubertal onset of retinitis pigmentosa (RP) and severe vestibular dysfunctions. Those with USH2 have moderate to severe congenital hearing loss, non-vestibular dysfunction and a later onset of RP. USH3 is characterized by variable RP and vestibular dysfunction combined with progressive hearing loss. The gene products of eight identified USH genes belong to different protein classes and families. There are five known USH1 molecules: the molecular motor myosin VIIa (USH1B); the two cell-cell adhesion cadherin proteins, cadherin 23 (USH1D) and protocadherin 15, (USH1F) and the scaffold proteins, harmonin (USH1C) and SANS (USH1G). In addition, two USH2 genes and one USH3A gene have been identified. The two USH2 genes code for the transmembrane protein USH2A, also termed USH2A ("usherin") and the G-protein-coupled 7-transmembrane receptor VLGR1b (USH2C), respectively, whereas the USH3A gene encodes clarin-1, a member of the clarin family which exhibits 4-transmembrane domains. Molecular analysis of USH1 protein function revealed that all five USH1 proteins are integrated into a protein network via binding to PDZ domains in the USH1C protein harmonin. Furthermore, this scaffold function of harmonin is supported by the USH1G protein SANS. Recently, we have shown that the USH2 proteins USH2A and VLGR1b as well as the candidate for USH2B, the sodium bicarbonate co-transporter NBC3, are also integrated into this USH protein network. In the inner ear, these interactions are essential for the differentiation of hair cell stereocilia but may also participate in the mechano-electrical signal transduction and the synaptic function of maturated hair cells. In the retina, the co-expression of all USH1 and USH2 proteins at the synapse of photoreceptor cells indicates that they are organized in an USH protein network there. The identification of the USH protein network indicates a common pathophysiological pathway in USH. Dysfunction or absence of any of the molecules in the mutual "interactome" related to the USH disease may lead to disruption of the network causing senso-neuronal degeneration in the inner ear and the retina, the clinical symptoms of USH.

The human Usher syndrome (USH) is the most common form of deaf-blindness. Usher type I (USH1), the most severe form, is characterized by profound congenital deafness, constant vestibular dysfunction and prepubertal onset of retinitis pigmentosa. Five corresponding genes of the seven USH1 genes have been cloned over the years. Recent studies indicated that three USH1 proteins, namely myosin VIIa (USH1B), SANS (USH1G), and cadherin 23 (USH1D) interact with the USH1C gene product harmonin. In these protein-protein complexes harmonin acts as the scaffold protein binding these USH1 molecules via its PDZ domains. The aim of the present study was to analyze whether or not the fifth identified USH1 protein protocadherin 15 (Pcdh15) also binds to harmonin and where these putative protein complexes might be localized in mammalian rod and cone photoreceptor cells.In vitro binding assays (GST pull-down, yeast two-hybrid assay) were applied. Antibodies against bacterial expressed USH1 proteins were generated. Affinity purified antibodies were used in immunoblot analyses of brain fractions and isolated retinas, in immunofluorescence studies, and in immunoelectron microscopic studies of rodent retinas.We showed that Pcdh15 (USH1F) interacted with harmonin PDZ2. Immunocytochemistry revealed that Pcdh15 is expressed in photoreceptor cells of the mammalian retina, where it is colocalized with harmonin, myosin VIIa, and cadherin 23 at the synaptic terminal. Colocalization of Pcdh15 with harmonin was found at the base of the photoreceptor outer segment, where newly synthesized disk membranes are present.Our data indicate that harmonin-Pcdh15 interactions probably play a role in disk morphogenesis. Furthermore, we provide evidence that a complex composed of all USH1 molecules may assemble at the photoreceptor synapse. This USH protein complex can contribute to the cortical cytoskeletal matrices of the pre- and postsynaptic regions, which are thought to play a fundamental role in the structural and functional organization of the synaptic junction. Defects in any of the USH1-complex partners may result in photoreceptor dysfunction causing retinitis pigmentosa, the clinical phenotype in the retina of USH1 patients.

Contains fulltext : 48386.pdf (Publisher’s version ) (Closed access) Usher syndrome (USH) is the most frequent cause of combined deaf-blindness in man. USH is clinically and genetically heterogeneous with at least 11 chromosomal loci assigned to the three USH types (USH1A-G, USH2A-C, USH3A). Although the different USH types exhibit almost the same phenotype in human, the identified USH genes encode for proteins which belong to very different protein classes and families. We and others recently reported that the scaffold protein harmonin (USH1C-gene product) integrates all identified USH1 molecules in a USH1-protein network. Here, we investigated the relationship between the USH2 molecules and this USH1-protein network. We show a molecular interaction between the scaffold protein harmonin (USH1C) and the USH2A protein, VLGR1 (USH2C) and the candidate for USH2B, NBC3. We pinpoint these interactions to interactions between the PDZ1 domain of harmonin and the PDZ-binding motifs at the C-termini of the USH2 proteins and NBC3. We demonstrate that USH2A, VLGR1 and NBC3 are co-expressed with the USH1-protein harmonin in the synaptic terminals of both retinal photoreceptors and inner ear hair cells. In hair cells, these USH proteins are also localized in the signal uptaking stereocilia. Our data indicate that the USH2 proteins and NBC3 are further partners in the supramolecular USH-protein network in the retina and inner ear which shed new light on the function of USH2 proteins and the entire USH-protein network. These findings provide first evidence for a molecular linkage between the pathophysiology in USH1 and USH2. The organization of USH molecules in a mutual 'interactome' related to the disease can explain the common phenotype in USH.

Cadherins are Ca2+-binding, transmembrane proteins involved in cell adhesion. Recently, three cadherin molecules, cadherin-23, protocadherin-15, and cadherin-3, were found to be defective in various human diseases, many of them with photoreceptor degeneration and/or sensorineural hearing loss as major features such Usher syndrome type 1D (USH1D), USH1F, and hypotrichosis with juvenile macular dystrophy. The process, by which mutations lead to photoreceptor degeneration is still not fully understood. Data from the inner ear phenotype of USH1 mouse models suggest that loss of cell adhesion is a crucial event.

PURPOSE. Human Usher syndrome is the most common form of combined deafness and blindness. Usher type I (USH1), the most severe form, is characterized by profound congenital deafness, constant vestibular dysfunction, and prepubertal onset retinitis pigmentosa. Previous studies have shown that the USH1-proteins myosin VIIa, harmonin, and cadherin 23 interact and form a functional network during hair cell differentiation in the inner ear. The purpose of the present study was to analyze the molecular and cellular functions of these USH1 proteins in the mammalian retina. METHODS. Antibodies to USH1 proteins were generated and used in Western blot analysis of subcellular photoreceptor fractions and immunofluorescence and electron microscopy of the retina. RESULTS. Splice variants of harmonin were differentially expressed in the photoreceptor cell compartments. Whereas harmonin b isoforms were restricted to the light-sensitive outer segment, the harmonin a and c isoforms were more ubiquitously distributed in the photoreceptors. At the synaptic terminal of photoreceptor cells, harmonin a and c colocalized with myosin VIIa and cadherin 23. CONCLUSIONS. USH1 molecules can assemble to a supramolecular complex at photoreceptor synapses. Such a complex may contribute to the cortical cytoskeletal matrices of the pre- and postsynaptic regions, which are thought to play a fundamental role in the organization of synaptic junctions. Dysfunction of any of the USH1 complex partners may lead to synaptic dysfunction causing retinitis pigmentosa, the clinical phenotype in the retina of patients with USH1. Furthermore, in photoreceptor outer segments, harmonin may also contribute to the clustering of outer segment proteins into supramolecular complexes.