Photostress Recovery Time as a Potential Predictive Biomarker for Age-Related Macular Degeneration

Abstract Purpose: The purpose of this study was to assess recovery time following photostress and its association with age-related macular degeneration (AMD) cross-sectionally and longitudinally in an elderly population-based cohort. Methods: We analyzed photostress recovery time (PRT) and AMD in >1800 AugUR study participants aged 70+ years. On color fundus images from baseline and 3-year follow-up, presence of AMD was graded manually (Three Continent AMD Consortium Severity Scale). Visual acuity (VA) was assessed via Early Treatment Diabetic Retinopathy Study (ETDRS) charts. After a 30-second bleaching of the macular region via direct ophthalmoscope, PRT was measured as the seconds to regain VA. Results: First, we analyzed 1208 AugUR participants cross-sectionally (288 with early AMD, and 78 with late AMD). Prolonged PRT was associated with early and late AMD versus no AMD (median PRT = 119.5, 198.0 versus 80.0 seconds, respectively; logistic regression odds ratio [OR] = 1.109–1.165 per 10 seconds, P values < 0.0001). Sensitivity analyses using alternative models or restricting to participants after cataract surgery revealed similar ORs. Second, the association was confirmed in an independent cross-sectional AugUR sample (n = 486). Third, in longitudinal analysis of 233 AugUR participants without AMD, prolonged PRT was associated with incident AMD ascertained 3 years later (follow-up time = 3.2 ± 0.2 years, OR = 1.112–1.162 per 10 seconds, P < 0.05). Overall, we demonstrate a significant association of prolonged PRT with AMD cross-sectionally and longitudinally in elderly individuals. Conclusions: Prolonged PRT might capture retinal function impairment after cell damage before early AMD is visible via color fundus imaging. Translational Relevance: Our results suggest PRT as quantitative predictive biomarker for incident AMD, making it potentially worthwhile also for clinical care

Genetic Risk Score Analysis Supports a Joint View of Two Classification Systems for Age-Related Macular Degeneration

Purpose: The purpose of this study was to evaluate the utility of combining the Clinical Classification (CC) and the Three Continent age-related macular degeneration (AMD) Consortium Severity Scale (3CACSS) for classification of AMD. Methods: In two independent cross-sectional datasets of our population-based AugUR study (Altersbezogene Untersuchungen zur Gesundheit der Universität Regensburg), we graded AMD via color fundus images applying two established classification systems (CC and 3CACSS). We calculated the genetic risk score (GRS) across 50 previously identified variants for late AMD, its association via logistic regression, and area under the curve (AUC) for each AMD stage. Results: We analyzed 2188 persons aged 70 to 95 years. When comparing the two classification systems, we found a distinct pattern: CC “age-related changes” and CC “early AMD” distinguished individuals with 3CACSS “no AMD”; 3CACSS “mild/moderate/severe early AMD” stages, and distinguished CC “intermediate AMD”. This suggested a 7-step scale combining the 2 systems: (i) “no AMD”, (ii) “age-related changes”, (iii) “very early AMD”, (i.e. CC “early”), (iv) “mild early AMD”, (v) “moderate early AMD”, (vi) “severe early AMD”, and (vii) “late AMD”. GRS association and diagnostic accuracy increased stepwise by increased AMD severity in the 7-step scale and by increased restriction of controls (e.g. for CC “no AMD without age-related changes”: AUC = 55.1%, 95% confidence interval [CI] = 51.6, 58.6, AUC = 62.3%, 95% CI = 59.1, 65.6, AUC = 63.8%, 95% CI = 59.3, 68.3, AUC = 78.1%, 95% CI = 73.6, 82.5, AUC = 82.2%, 95% CI = 78.4, 86.0, and AUC = 79.2%, 95% CI = 75.4, 83.0). A stepwise increase was also observed by increased drusen size and area. Conclusions: The utility of a 7-step scale is supported by our clinical and GRS data. This harmonization and full data integration provides an immediate simplification over using either CC or 3CACSS and helps to sharpen the control group

A Timescale for Evolution, Population Expansion, and Spatial Spread of an Emerging Clone of Methicillin-Resistant Staphylococcus aureus

Due to the lack of fossil evidence, the timescales of bacterial evolution are largely unknown. The speed with which genetic change accumulates in populations of pathogenic bacteria, however, is a key parameter that is crucial for understanding the emergence of traits such as increased virulence or antibiotic resistance, together with the forces driving pathogen spread. Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of hospital-acquired infections. We have investigated an MRSA strain (ST225) that is highly prevalent in hospitals in Central Europe. By using mutation discovery at 269 genetic loci (118,804 basepairs) within an international isolate collection, we ascertained extremely low diversity among European ST225 isolates, indicating that a recent population bottleneck had preceded the expansion of this clone. In contrast, US isolates were more divergent, suggesting they represent the ancestral population. While diversity was low, however, our results demonstrate that the short-term evolutionary rate in this natural population of MRSA resulted in the accumulation of measurable DNA sequence variation within two decades, which we could exploit to reconstruct its recent demographic history and the spatiotemporal dynamics of spread. By applying Bayesian coalescent methods on DNA sequences serially sampled through time, we estimated that ST225 had diverged since approximately 1990 (1987 to 1994), and that expansion of the European clade began in 1995 (1991 to 1999), several years before the new clone was recognized. Demographic analysis based on DNA sequence variation indicated a sharp increase of bacterial population size from 2001 to 2004, which is concordant with the reported prevalence of this strain in several European countries. A detailed ancestry-based reconstruction of the spatiotemporal dispersal dynamics suggested a pattern of frequent transmission of the ST225 clone among hospitals within Central Europe. In addition, comparative genomics indicated complex bacteriophage dynamics

Characterization of the ribosome-associated complex RAC from S. cerevisiae

Zuotin and Ssz from yeast are members of the conserved Hsp40 and Hsp70 family of molecular chaperones, respectively, and are thought to be involved in the folding of newly synthesized proteins. Hsp70s use an ATP-controlled cycle for substrate binding and release which is regulated by their Hsp40 co-chaperones. However, in contrast to canonical Hsp70/40 members, Zuotin and Ssz form an unusually stable heterodimer termed ribosome-associated complex (RAC), which is bound to the ribosome. Thus RAC acts as a co-chaperone for another ribosome-bound Hsp70, Ssb. The aim of this thesis was to elucidate the unusual pairing of RAC and the influence of ATP on the complex by investigating the conformational changes and dynamics in solution. These conformational studies were performed using amide hydrogen exchange (HX) combined with high resolution mass pectrometry (MS). Additional analyses were conducted using mutational analyses, fluorescence measurements and electron paramagnetic resonance (EPR) measurements. HX-MS experiments with recombinant, purified S. cerevisiae Ssz, revealed specific ATP-induced conformational changes in Ssz individually and in complex. Upon ATP binding the nucleotide binding domain (NBD) was stabilized, resulting in a more compact structure. However, in contrast to canonical Hsp70s no influence of ATP binding on the substrate binding domain (SBD) was observed. Complex formation did not influence the nucleotide binding domain, but decreased the conformational dynamics within the SBD, indicating the engagement of the SBD in complex formation. Biochemical binding analysis of the individual domains NBD and SBD, respectively, revealed an interaction of the NBD of Ssz with the N-terminal domain of its complex partner Zuo. This indicates an involvement of both domains (NBD and SBD of Ssz) in complex formation of RAC. HX-MS experiments with recombinant, purified S. cerevisiae Zuo, revealed an extremely flexible region at the beginning of the N-terminal region of Zuo (aa 1 - 79). Upon complex formation this structure was conformationally stabilized, leaving only a short linker-like-region (aa 53 - 79) unstructured. Deletion of the highly flexible Nterminus of Zuo abolished stable association with Ssz in vitro and caused a phenotype resembling the loss of Ssz’s function in vivo. Thus, the C-terminal domain of Ssz, the N-terminal extension of Zuo and their mutual stabilization are the major structural determinants for RAC assembly. Moreover, HX-MS experiments revealed dynamic changes in the J-domain of Zuo upon complex formation that might be crucial for RAC’s co-chaperone function. Further EPR analysis using cysteine mutants of Zuo indicated that the conformational changes are not restricted to the interacting HPD motif itself but rather to the whole J-domain. The results obtained in this work allowed to develop a model presenting a novel mechanism for converting Zuo and Ssz chaperones into a functionally active heterodimer

Erhebung von Kurz- und Langzeiteffekten nach einem Videofluoroskopie-Trainingsprogramm unter Berücksichtigung visuell-räumlicher Einflüsse

Strakeljahn F, Uppenkamp K, Richter K, Wilmskötter J, Müller HM, Stanschus S. Erhebung von Kurz- und Langzeiteffekten nach einem Videofluoroskopie-Trainingsprogramm unter Berücksichtigung visuell-räumlicher Einflüsse. Dysphagieforum. 2014;2014(1):3-16

Structural Analysis of the Ribosome-associated Complex (RAC) Reveals an Unusual Hsp70/Hsp40 Interaction

Yeast Zuotin and Ssz are members of the conserved Hsp40 and Hsp70 chaperone families, respectively, but compared with canonical homologs, they atypically form a stable heterodimer termed ribosome-associated complex (RAC). RAC acts as co-chaperone for another Hsp70 to assist de novo protein folding. In this study, we identified the molecular basis for the unusual Hsp70/Hsp40 pairing using amide hydrogen exchange (HX) coupled with mass spectrometry and mutational analysis. Association of Ssz with Zuotin strongly decreased the conformational dynamics mainly in the C-terminal domain of Ssz, whereas Zuotin acquired strong conformational stabilization in its N-terminal segment. Deletion of the highly flexible N terminus of Zuotin abolished stable association with Ssz in vitro and caused a phenotype resembling the loss of Ssz function in vivo. Thus, the C-terminal domain of Ssz, the N-terminal extension of Zuotin, and their mutual stabilization are the major structural determinants for RAC assembly. We furthermore found dynamic changes in the J-domain of Zuotin upon complex formation that might be crucial for RAC co-chaperone function. Taken together, we present a novel mechanism for converting Zuotin and Ssz chaperones into a functionally active dimer

Cleaning robot navigation using panoramic views and particle clouds as landmarks

Möller R, Krzykawski M, Gerstmayr-Hillen L, Horst M, Fleer DR, de Jong J. Cleaning robot navigation using panoramic views and particle clouds as landmarks. Robotics and Autonomous Systems. 2013;61(12):1415-1439