Characterization of the Usher Syndrome gene CDH23: implications for mechanosensation in the vertebrate inner ear

Deafness is the most common form of sensory impairment afflicting the human population. Approximately one in eight hundred children is born with serious hearing impairment and more than half of these cases are likely due to single gene defects. In addition to hearing loss, mutations in some genes cause Usher Syndrome, not only affecting the auditory apparatus but also causing visual impairment eventually leading to blindness. Several genetic loci have been linked to Usher Syndrome Type I, the most severe form of the disease, and so far five of the relevant genes have been identified. Understanding their molecular role in the context of ear and retina physiology will be invaluable to the design of effective therapies against this devastating disease. Some forms of Usher Syndrome as well as other hearing disorders are caused by defects in the inner ear that contains the end organs for the perception of sound waves, the cochlea, and for the detection of gravity and acceleration, the vestibule. Both end organs contain mechanosensory hair cells that are named after actin rich stereocilia projecting from their apical surface. The stereocilia contain mechanically gated ion channels that open or close upon deflection of the stereocilia. This in turn triggers ion influx into the hair cells, causing changes in cell polarization and alterations in the rate of neurotransmitter release from the hair cells onto innervating neurons. The mechanically gated transduction channel implicated in this event has remained elusive. Mechanical gating of the transduction channel is believed to be triggered by thin filaments, the tip links, connecting adjacent stereocilia into a bundle. It has been suggested that these connector molecules are being stretched during hair cell stimulation, thereby actively pulling open the transduction channel. Although these filaments are clearly detectable on the ultrastructural level, their molecular nature has remained elusive. One molecule that might participate in mechanoelectrical transduction is the transmembrane protein cadherin 23 (CDH23). Mutations in its gene can cause Usher Syndrome, non-syndromic forms deafness and age-related hearing loss in human patients. Mice and zebrafish that carry mutations in the orthologous genes show splayed stereocilia bundle morphology, arguing for a function of the protein product in the cell compartment harboring the transduction channel. Furthermore, CDH23 is large enough to be the tip link, the extracellular filament proposed to gate the mechanotransduction channel. Here we show that antibodies against CDH23 label the entire stereocilia bundle during hair cell morphogenesis. In mature hair cells CDH23 labelling is confined to the tip links. Further, CDH23 has biochemical properties similar to those of the tip link. In cell-aggregation experiments CDH23 displays Ca2+-dependent, homophilic adhesion potential, an attribute typically observed for members of the cadherin superfamily, which may explain how adjacent stereocilia are linked together. Moreover, CDH23 forms a complex with myosin 1c (MYO1C), the only known component of the mechanotransduction apparatus, suggesting that CDH23 and MYO1C cooperate to regulate the activity of mechanically gated ion channels in hair cells. Computer assisted alignments with sequences encoding the cytosolic domain of CDH23 reveal two putative PDZ-binding motifs. Others and we can show that CDH23 interacts with the product of a second Usher Syndrome gene, harmonin. Two PDZ domains within harmonin interact with two complementary binding surfaces in the CDH23 cytoplasmic domain. One of the binding surfaces is disrupted by sequences encoded by an alternatively spliced CDH23 exon that is expressed in hair cells, but not in any other tissue analyzed so far. In the ear, harmonin is expressed in the stereocilia of developing hair cells. Since mice with a targeted deletion of the harmonin gene have been reported to phenocopy the splayed stereocilia bundle morphology observed in CDH23 deficient mice, the complex of the two Usher Syndrome proteins is predicted to be important for the stereocilia bundle. Whether the harmonin–CDH23 complex might be involved in mechanotransduction is unclear, since harmonin´s presence in mature stereocilia has not been reported yet. We concluded that CDH23 may serve a dual function in auditory hair cells: together with harmonin the molecule is important to shape the hair bundle during hair bundle morphogenesis and in mature stereocilia the molecule is part of the tip link complex

Nitrogen fertilizer fate after introducing maize and upland-rice into continuous paddy rice cropping systems

Water scarcity and economic incentives favor the introduction of upland crops into permanent paddy rice systems during dry seasons. However, introducing upland crops into permanently flooded cropping systems temporarily changes soil conditions from anaerobic to aerobic, affecting nitrogen (N) dynamics profoundly. We hypothesized that under maize and dry rice, total fertilizer $^{15}$N recovery in soil as well as the immobilization of fertilizer $^{15}$N in microbial residues is reduced compared with continuous paddy rice cropping. Furthermore, we expected enhanced emissions of fertilizer $^{15}$N in form of nitrous oxide (N₂O) under maize and dry rice. To test these hypotheses, we traced the fate of a $^{15}$N-urea pulse in a field experiment in the Philippines with three different crop rotations: continuous paddy rice, paddy rice – dry rice, and paddy rice – maize for two years. Indeed, the $^{15}$N recovery in the first 5 cm of bulk soil was lowest in the paddy rice – maize rotation (arithmetic mean with standard error: 19.2 ± 1.8% of applied $^{15}$N), while twice as much was recovered in the first 5 cm of bulk soil of the continuous paddy rice cropping systems (37.8 ± 2.2% of applied $^{15}$N) during the first dry season. The $^{15}$N recovery in the plant biomass (shoots and roots) in the continuous paddy rice cropping was 13% larger than in the dry rice plant biomass and 5% larger than in the maize plant biomass during the first dry season. Fertilizer $^{15}$N remained longest in paddy rice – maize (mean residence time=90 ± 25 days) and in continuous paddy rice (mean residence time=77 ± 30 days), compared with dry rice – paddy rice rotation (mean residence time=16 ± 5 days). After 2 years, 10% (paddy rice – dry rice, paddy rice – maize) to 23% (continuous paddy rice) of the applied fertilizer 15N were still stored in soil. The largest fraction of this $^{15}$N was immobilized by soil microbes, which stored 3-4% of applied 15N in the form of amino sugars as specific cell wall constituents, in all cropping systems. Nevertheless, introducing upland crops into continuous paddy rice systems likely increased N leaching losses and resulted in initial losses of urea- $^{15}$N to N₂O, which thus has to be considered in climate smart mitigation strategies

Взаємодія системи "політика-релігія"

Досліджено феномен суспільних явищ політики і релігії у перерізі їх взаємодії, вивчено історичний досвід такого взаємного впливу. Окреме місце відведено аналізу практичного застосування закону України “Про свободу совісті та релігійні організації”.The article explores the phenomenon of social phenomena politics and religion in the context of their interaction, exploring the historical experience of such mutual influence. A separate analysis is given to the practical application of the Law of Ukraine “On Freedom of Conscience and Religious Organizations”

The nitrogen, carbon and greenhouse gas budget of a grazed, cut and fertilised temperate grassland

Intensively managed grazed grasslands in temperate climates are globally important environments for the exchange of the greenhouse gases (GHGs) carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4). We assessed the N and C budget of a mostly grazed and occasionally cut and fertilised grassland in SE Scotland by measuring or modelling all relevant imports and exports to the field as well as changes in soil C and N stocks over time. The N budget was dominated by import from inorganic and organic fertilisers (21.9 g N m−2 a−1) and losses from leaching (5.3 g N m−2 a−1), N2 emissions (2.9 g N m−2 a−1), and NOx and NH3 volatilisation (3.9 g N m−2 a−1), while N2O emission was only 0.6 g N m−2 a−1. The efficiency of N use by animal products (meat and wool) averaged 9.9 % of total N input over only-grazed years (2004–2010). On average over 9 years (2002–2010), the balance of N fluxes suggested that 6.0 ± 5.9 g N m−2 a−1 (mean ± confidence interval at p > 0.95) were stored in the soil. The largest component of the C budget was the net ecosystem exchange of CO2 (NEE), at an average uptake rate of 218 ± 155 g C m−2 a−1 over the 9 years. This sink strength was offset by carbon export from the field mainly as grass offtake for silage (48.9 g C m−2 a−1) and leaching (16.4 g C m−2 a−1). The other export terms, CH4 emissions from the soil, manure applications and enteric fermentation, were negligible and only contributed to 0.02–4.2 % of the total C losses. Only a small fraction of C was incorporated into the body of the grazing animals. Inclusion of these C losses in the budget resulted in a C sink strength of 163 ± 140 g C m−2 a−1. By contrast, soil stock measurements taken in May 2004 and May 2011 indicated that the grassland sequestered N in the 0–60 cm soil layer at 4.51 ± 2.64 g N m−2 a−1 and lost C at a rate of 29.08 ± 38.19 g C m−2 a−1. Potential reasons for the discrepancy between these estimates are probably an underestimation of C losses, especially from leaching fluxes as well as from animal respiration. The average greenhouse gas (GHG) balance of the grassland was −366 ± 601 g CO2 eq. m−2 yr−1 and was strongly affected by CH4 and N2O emissions. The GHG sink strength of the NEE was reduced by 54 % by CH4 and N2O emissions. Estimated enteric fermentation from ruminating sheep proved to be an important CH4 source, exceeding the contribution of N2O to the GHG budget in some years

The Wooster Voice (Wooster, OH), 1949-12-08

Dr. T. Cuyler Young addresses the campus during the annual Wooster Day celebration. Dr. Delbert Lean will give his 40th annual reading of Charles Dickens\u27 Christmas Carol. Plans to build a darkroom for student publications are announced. Additionally, Wooster host the fall conference of the Ohio division of the National Student Association.https://openworks.wooster.edu/voice1941-1950/1204/thumbnail.jp