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- Amblyopia (3)
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- Eccentric fixation (3)
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Background: Gastrulation is a key transition in embryogenesis; it requires self-organized cellular coordination, which has to be both robust to allow efficient development and plastic to provide adaptability. Despite the conservation of gastrulation as a key event in Metazoan embryogenesis, the morphogenetic mechanisms of self-organization (how global order or coordination can arise from local interactions) are poorly understood.
Results: We report a modular structure of cell internalization in Caenorhabditis elegans gastrulation that reveals mechanisms of self-organization. Cells that internalize during gastrulation show apical contractile flows, which are correlated with centripetal extensions from surrounding cells. These extensions converge to seal over the internalizing cells in the form of rosettes. This process represents a distinct mode of monolayer remodeling, with gradual extrusion of the internalizing cells and simultaneous tissue closure without an actin purse-string. We further report that this self-organizing module can adapt to severe topological alterations, providing evidence of scalability and plasticity of actomyosin-based patterning. Finally, we show that globally, the surface cell layer undergoes coplanar division to thin out and spread over the internalizing mass, which resembles epiboly.
Conclusions: The combination of coplanar division-based spreading and recurrent local modules for piecemeal internalization constitutes a system-level solution of gradual volume rearrangement under spatial constraint. Our results suggest that the mode of C. elegans gastrulation can be unified with the general notions of monolayer remodeling and with distinct cellular mechanisms of actomyosin-based morphogenesis.
Autophagy can act either as a tumor suppressor or as a survival mechanism for established tumors. To understand how autophagy plays this dual role in cancer, in vivo models are required. By using a highly heterogeneous C. elegans germline tumor, we show that autophagy-related proteins are expressed in a specific subset of tumor cells, neurons. Inhibition of autophagy impairs neuronal differentiation and increases tumor cell number, resulting in a shorter life span of animals with tumors, while induction of autophagy extends their life span by impairing tumor proliferation. Fasting of animals with fully developed tumors leads to a doubling of their life span, which depends on modular changes in transcription including switches in transcription factor networks and mitochondrial metabolism. Hence, our results suggest that metabolic restructuring, cell-type specific regulation of autophagy and neuronal differentiation constitute central pathways preventing growth of heterogeneous tumors.
Cephalization is a major innovation of animal evolution and implies a synchronization of nervous system, mouth, and foregut polarization to align alimentary tract and sensomotoric system for effective foraging. However, the underlying integration of morphogenetic programs is poorly understood. Here, we show that invagination of neuroectoderm through de novo polarization and apical constriction creates the mouth opening in the Caenorhabditis elegans embryo. Simultaneously, all 18 juxta-oral sensory organ dendritic tips become symmetrically positioned around the mouth: While the two bilaterally symmetric amphid sensilla endings are towed to the mouth opening, labial and cephalic sensilla become positioned independently. Dendrite towing is enabled by the pre-polarized sensory amphid pores intercalating into the leading edge of the anteriorly migrating epidermal sheet, while apical constriction-mediated cell–cell re-arrangements mediate positioning of all other sensory organs. These two processes can be separated by gradual inactivation of the 26S proteasome activator, RPN-6.1. Moreover, RPN- 6.1 also shows a dose-dependent requirement for maintenance of coordinated apical polarization of other organs with apical lumen, the pharynx, and the intestine. Thus, our data unveil integration of morphogenetic programs during the coordination of alimentary tract and sensory organ formation and suggest that this process requires tight control of ubiquitin-dependent protein degradation.
Formation of the anteroposterior and dorsoventral body axis in Caenorhabditis elegans depends on cortical flows and advection of polarity determinants. The role of this patterning mechanism in tissue polarization after formation of cell-cell contacts is not fully understood. Here, we demonstrate that planar asymmetries are established during left-right symmetry breaking: Centripetal cortical flows asymmetrically and differentially advect anterior polarity determinants (aPARs) from contacts to the medial cortex, resulting in their unmixing from apical myosin. Contact localization and advection of PAR-6 requires balanced CDC-42 activation, while asymmetric retention and advection of PAR-3 can occur independently of PAR-6. Concurrent asymmetric retention of PAR-3, E-cadherin/HMR-1 and opposing retention of antagonistic CDC-42 and Wnt pathway components leads to planar asymmetries. The most obvious mark of planar asymmetry, retention of PAR-3 at a single cell-cell contact, is required for proper cytokinetic cell intercalation. Hence, our data uncover how planar polarity is established in a system without the canonical planar cell polarity pathway through planar asymmetric retention of aPARs.
Selfish genetic elements that act as post-segregation distorters cause lethality in non-carrier individuals after fertilization. Two post-segregation distorters have been previously identified in Caenorhabditis elegans, the peel-1/zeel-1 and the sup-35/pha-1 elements. These elements seem to act as modification-rescue systems, also called toxin/antidote pairs. Here we show that the maternal-effect toxin/zygotic antidote pair sup-35/pha-1 is required for proper expression of apical junction (AJ) components in epithelia and that sup-35 toxicity increases when pathways that establish and maintain basal epithelial characteristics, die-1, elt-1, lin-26, and vab-10, are compromised. We demonstrate that pha-1(e2123) embryos, which lack the antidote, are defective in epidermal morphogenesis and frequently fail to elongate. Moreover, seam cells are frequently misshaped and mispositioned and cell bond tension is reduced in pha-1(e2123) embryos, suggesting altered tissue material properties in the epidermis. Several aspects of this phenotype can also be induced in wild-type embryos by exerting mechanical stress through uniaxial loading. Seam cell shape, tissue mechanics, and elongation can be restored in pha-1(e2123) embryos if expression of the AJ molecule DLG-1/Discs large is reduced. Thus, our experiments suggest that maternal-effect toxicity disrupts proper development of the epidermis which involves distinct transcriptional regulators and AJ components.
Purpose: Amblyopia with eccentric fixation, especially when not diagnosed early, is a therapeutic challenge, as visual outcome is known to be poorer than in amblyopia with central fixation. Consequently, treatment after late diagnosis is often denied. Electronic monitoring of occlusion provides us the chance to gain first focussed insight into age-dependent dose response and treatment efficiency, as well as the shift of fixation in this rare group of paediatric patients. Methods: In our prospective pilot study, we examined amblyopes with eccentric fixation during 12 months of occlusion treatment. We evaluated their visual acuity, recorded patching duration using a TheraMon®-microsensor, and determined their fixation with a direct ophthalmoscope. Dose-response relationship and treatment efficiency were calculated. Results: The study included 12 participants with strabismic and combined amblyopia aged 2.9–12.4 years (mean 6.5). Median prescription of occlusion was 7.7 h/day (range 6.6–9.9) and median daily received occlusion was 5.2 h/day (range 0.7–9.7). At study end, median acuity gain was 0.6 log units (range 0–1.6) and residual interocular visual acuity difference (IOVAD) 0.3 log units (range 0–1.8). There was neither significant acuity gain nor reduction in IOVAD after the 6th month of treatment. Children younger than 4 years showed best response with lowest residual IOVAD at study end. Efficiency calculation showed an acuity gain of approximately one line from 100 h of patching in the first 2 months and half a line after 6 months. There was a significant decline of treatment efficiency with age (p = 0.01). Foveolar fixation was achieved after median 3 months (range 1–6). Three patients (> 6 years) did not gain central fixation. Conclusion: Eccentric fixation is a challenge to therapy success. Based on electronic monitoring, our study quantified for the first time the reduction of treatment efficiency with increasing age in amblyopes with eccentric fixation. Despite some improvement in patients up to 8 years, older patients showed significantly lower treatment efficiency. In younger patients with good adherence, despite poor initial acuity, central fixation and low residual IOVAD could be attained after median 3 months. Hence, the necessity of early diagnosis and intensive occlusion should be emphasized.
Purpose: Amblyopia with eccentric fixation, especially when not diagnosed early, is a therapeutic challenge, as visual outcome is known to be poorer than in amblyopia with central fixation. Consequently, treatment after late diagnosis is often denied. Electronic monitoring of occlusion provides us the chance to gain first focussed insight into age-dependent dose response and treatment efficiency, as well as the shift of fixation in this rare group of paediatric patients. Methods: In our prospective pilot study, we examined amblyopes with eccentric fixation during 12 months of occlusion treatment. We evaluated their visual acuity, recorded patching duration using a TheraMon®-microsensor, and determined their fixation with a direct ophthalmoscope. Dose-response relationship and treatment efficiency were calculated. Results: The study included 12 participants with strabismic and combined amblyopia aged 2.9–12.4 years (mean 6.5). Median prescription of occlusion was 7.7 h/day (range 6.6–9.9) and median daily received occlusion was 5.2 h/day (range 0.7–9.7). At study end, median acuity gain was 0.6 log units (range 0–1.6) and residual interocular visual acuity difference (IOVAD) 0.3 log units (range 0–1.8). There was neither significant acuity gain nor reduction in IOVAD after the 6th month of treatment. Children younger than 4 years showed best response with lowest residual IOVAD at study end. Efficiency calculation showed an acuity gain of approximately one line from 100 h of patching in the first 2 months and half a line after 6 months. There was a significant decline of treatment efficiency with age (p = 0.01). Foveolar fixation was achieved after median 3 months (range 1–6). Three patients (> 6 years) did not gain central fixation. Conclusion: Eccentric fixation is a challenge to therapy success. Based on electronic monitoring, our study quantified for the first time the reduction of treatment efficiency with increasing age in amblyopes with eccentric fixation. Despite some improvement in patients up to 8 years, older patients showed significantly lower treatment efficiency. In younger patients with good adherence, despite poor initial acuity, central fixation and low residual IOVAD could be attained after median 3 months. Hence, the necessity of early diagnosis and intensive occlusion should be emphasized.
Purpose: Amblyopia with eccentric fixation, especially when not diagnosed early, is a therapeutic challenge, as visual outcome is known to be poorer than in amblyopia with central fixation. Consequently, treatment after late diagnosis is often denied. Electronic monitoring of occlusion provides us the chance to gain first focussed insight into age-dependent dose response and treatment efficiency, as well as the shift of fixation in this rare group of paediatric patients. Methods: In our prospective pilot study, we examined amblyopes with eccentric fixation during 12 months of occlusion treatment. We evaluated their visual acuity, recorded patching duration using a TheraMon®-microsensor, and determined their fixation with a direct ophthalmoscope. Dose-response relationship and treatment efficiency were calculated. Results: The study included 12 participants with strabismic and combined amblyopia aged 2.9–12.4 years (mean 6.5). Median prescription of occlusion was 7.7 h/day (range 6.6–9.9) and median daily received occlusion was 5.2 h/day (range 0.7–9.7). At study end, median acuity gain was 0.6 log units (range 0–1.6) and residual interocular visual acuity difference (IOVAD) 0.3 log units (range 0–1.8). There was neither significant acuity gain nor reduction in IOVAD after the 6th month of treatment. Children younger than 4 years showed best response with lowest residual IOVAD at study end. Efficiency calculation showed an acuity gain of approximately one line from 100 h of patching in the first 2 months and half a line after 6 months. There was a significant decline of treatment efficiency with age (p = 0.01). Foveolar fixation was achieved after median 3 months (range 1–6). Three patients (> 6 years) did not gain central fixation. Conclusion: Eccentric fixation is a challenge to therapy success. Based on electronic monitoring, our study quantified for the first time the reduction of treatment efficiency with increasing age in amblyopes with eccentric fixation. Despite some improvement in patients up to 8 years, older patients showed significantly lower treatment efficiency. In younger patients with good adherence, despite poor initial acuity, central fixation and low residual IOVAD could be attained after median 3 months. Hence, the necessity of early diagnosis and intensive occlusion should be emphasized.
Objectives: To investigate the prevalence of depressive symptoms in rheumatoid arthritis (RA) patients using two previously validated questionnaires in a large patient sample, and to evaluate depressive symptoms in the context of clinical characteristics (e.g. remission of disease) and patient-reported impact of disease.
Methods: In this cross-sectional study, the previously validated Patient Health Questionnaire (PHQ-9) and Beck-Depression Inventory II (BDI-II) were used to assess the extent of depressive symptoms in RA patients. Demographic background, RA disease activity score (DAS28), RA impact of disease (RAID) score, comorbidities, anti-rheumatic therapy and antidepressive treatment, were recorded. Cut-off values for depressive symptomatology were PHQ-9 ≥5 or BDI-II ≥14 for mild depressive symptoms or worse and PHQ-9 ≥ 10 or BDI-II ≥ 20 for moderate depressive symptoms or worse. Prevalence of depressive symptomatology was derived by frequency analysis while factors independently associated with depressive symptomatology were investigated by using multiple logistic regression analyses. Ethics committee approval was obtained, and all patients provided written informed consent before participation.
Results: In 1004 RA-patients (75.1% female, mean±SD age: 61.0±12.9 years, mean disease duration: 12.2±9.9 years, DAS28 (ESR): 2.5±1.2), the prevalence of depressive symptoms was 55.4% (mild or worse) and 22.8% (moderate or worse). Characteristics independently associated with depressive symptomatology were: age <60 years (OR = 1.78), RAID score >2 (OR = 10.54) and presence of chronic pain (OR = 3.25). Of patients classified as having depressive symptoms, only 11.7% were receiving anti-depressive therapy.
Conclusions: Mild and moderate depressive symptoms were common in RA patients according to validated tools. In routine clinical practice, screening for depression with corresponding follow-up procedures is as relevant as incorporating these results with patient-reported outcomes (e.g. symptom state), because the mere assessment of clinical disease activity does not sufficiently reflect the prevalence of depressive symptoms.
Clinical trial registration number: This study is registered in the Deutsches Register Klinischer Studien (DRKS00003231) and ClinicalTrials.gov (NCT02485483).
During animal development, it is crucial that cells can sense and adapt to mechanical forces from their environment. Ultimately, these forces are transduced through the actomyosin cortex. How the cortex can simultaneously respond to and create forces during cytokinesis is not well understood. Here we show that under mechanical stress, cortical actomyosin flow switches its polarization during cytokinesis in the C. elegans embryo. In unstressed embryos, longitudinal cortical flows contribute to contractile ring formation, while rotational cortical flow is additionally induced in uniaxially loaded embryos. Rotational cortical flow is required for the redistribution of the actomyosin cortex in loaded embryos. Rupture of longitudinally aligned cortical fibers during cortex rotation releases tension, initiates orthogonal longitudinal flow and thereby contributes to furrowing in loaded embryos. A targeted screen for factors required for rotational flow revealed that actomyosin regulators involved in RhoA regulation, cortical polarity and chirality are all required for rotational flow and become essential for cytokinesis under mechanical stress. In sum, our findings extend the current framework of mechanical stress response during cell division and show scaling of orthogonal cortical flows to the amount of mechanical stress.
