Centrosomal enrichment and proteasomal degradation of SYS-1/ß-catenin requires the microtubule motor dynein.

The Caenorhabditis elegans Wnt/ß-catenin asymmetry (WßA) pathway utilizes asymmetric regulation of SYS-1/ß-catenin and POP-1/TCF coactivators. WßA differentially regulates gene expression during cell fate decisions, specifically by asymmetric localization of determinants in mother cells to produce daughters biased toward their appropriate cell fate. Despite the induction of asymmetry, ß-catenin localizes symmetrically to mitotic centrosomes in both mammals and C. elegans. Owing to the mitosis-specific localization of SYS-1 to centrosomes and enrichment of SYS-1 at kinetochore microtubules when SYS-1 centrosomal loading is disrupted, we investigated active trafficking in SYS-1 centrosomal localization. Here, we demonstrate that trafficking by microtubule motor dynein is required to maintain SYS-1 centrosomal enrichment, by dynein RNA interference (RNAi)-mediated decreases in SYS-1 centrosomal enrichment and by temperature-sensitive allele of the dynein heavy chain. Conversely, we observe depletion of microtubules by nocodazole treatment or RNAi of dynein-proteasome adapter ECPS-1 exhibits increased centrosomal enrichment of SYS-1. Moreover, disruptions to SYS-1 or negative regulator microtubule trafficking are sufficient to significantly exacerbate SYS-1 dependent cell fate misspecifications. We propose a model whereby retrograde microtubule-mediated trafficking enables SYS-1 enrichment at centrosomes, enhancing its eventual proteasomal degradation. These studies support the link between centrosomal localization and enhancement of proteasomal degradation, particularly for proteins not generally considered "centrosomal."

Centrosomes are required for proper ß-catenin processing and Wnt response.

The Wnt/ß-catenin signaling pathway is central to metazoan development and routinely dysregulated in cancer. Wnt/ß-catenin signaling initiates transcriptional reprogramming upon stabilization of the transcription factor ß-catenin, which is otherwise posttranslationally processed by a destruction complex and degraded by the proteasome. Since various Wnt signaling components are enriched at centrosomes, we examined the functional contribution of centrosomes to Wnt signaling, ß-catenin regulation, and posttranslational modifications. In HEK293 cells depleted of centrosomes we find that ß-catenin synthesis and degradation rates are unaffected but that the normal accumulation of ß-catenin in response to Wnt signaling is attenuated. This is due to accumulation of a novel high-molecular-weight form of phosphorylated ß-catenin that is constitutively degraded in the absence of Wnt. Wnt signaling operates by inhibiting the destruction complex and thereby reducing destruction complex-phosphorylated ß-catenin, but high-molecular-weight ß-catenin is unexpectedly increased by Wnt signaling. Therefore these studies have identified a pool of ß-catenin effectively shielded from regulation by Wnt. We present a model whereby centrosomes prevent inappropriate ß-catenin modifications that antagonize normal stabilization by Wnt signals.

Identifying gaps in the continuum of care for cardiovascular disease and diabetes in two communities in South Africa: Baseline findings from the HealthRise project.

BACKGROUND: The HealthRise initiative seeks to implement and evaluate innovative community-based strategies for diabetes, hypertension and hypercholesterolemia along the entire continuum of care (CoC)-from awareness and diagnosis, through treatment and control. In this study, we present baseline findings from HealthRise South Africa, identifying gaps in the CoC, as well as key barriers to care for non-communicable diseases (NCDs). METHODS: This mixed-methods needs assessment utilized national household data, health facility surveys, focus group discussions, and key informant interviews in Umgungundlovu and Pixley ka Seme districts. Risk factor and disease prevalence were estimated from the South Africa National Health and Nutrition Examination Survey. Health facility surveys were conducted at 86 facilities, focusing on essential intervention, medications and standard treatment guidelines. Quantitative results are presented descriptively, and qualitative data was analyzed using a framework approach. RESULTS: 46.8% of the population in Umgungundlovu and 51.0% in Pixley ka Seme were hypertensive. Diabetes was present in 11.0% and 9.7% of the population in Umgungundlovu and Pixley ka Seme. Hypercholesterolemia was more common in Pixley ka Seme (17.3% vs. 11.1%). Women and those of Indian descent were more likely to have diabetes. More than half of the population was found to be overweight, and binge drinking, inactivity and smoking were all common. More than half of patients with hypertension were unaware of their disease status (51.6% in Pixley ka Seme and 51.3% in Umgungundlovu), while the largest gap in the diabetes CoC occurred between initiation of treatment and achieving disease control. Demand-side barriers included lack of transportation, concerns about confidentiality, perceived discrimination and long wait times. Supply-side barriers included limited availability of testing equipment, inadequate staffing, and pharmaceutical stock outs. CONCLUSION: In this baseline assessment of two South African health districts we found high rates of undiagnosed hypercholesterolemia and hypertension, and poor control of hypercholesterolemia, hypertension, and diabetes. The HealthRise Initiative will need to address key supply- and demand-side barriers in an effort to improve important NCD outcomes.

Public knowledge of cardiovascular disease and response to acute cardiac events in three cities in China and India.

OBJECTIVE: To inform interventions targeted towards reducing mortality from acute myocardial infarction (AMI) and sudden cardiac arrest in three megacities in China and India, a baseline assessment of public knowledge, attitudes and practices was performed. METHODS: A household survey, supplemented by focus group and individual interviews, was used to assess public understanding of cardiovascular disease (CVD) risk factors, AMI symptoms, cardiopulmonary resuscitation (CPR) and automated external defibrillators (AEDs). Additionally, information was collected on emergency service utilisation and associated barriers to care. RESULTS: 5456 household surveys were completed. Hypertension was most commonly recognised among CVD risk factors in Beijing and Shanghai (68% and 67%, respectively), while behavioural risk factors were most commonly identified in Bangalore (smoking 91%; excessive alcohol consumption 64%). Chest pain/discomfort was reported by at least 60% of respondents in all cities as a symptom of AMI, but 21% of individuals in Bangalore could not name a single symptom. In Beijing, Shanghai and Bangalore, 26%, 15% and 3% of respondents were trained in CPR, respectively. Less than one-quarter of participants in all cities recognised an AED. Finally, emergency service utilisation rates were low, and many individuals expressed concern about the quality of prehospital care. CONCLUSIONS: Overall, we found low to modest knowledge of CVD risk factors and AMI symptoms, infrequent CPR training and little understanding of AEDs. Interventions will need to focus on basic principles of CVD and its complications in order for patients to receive timely and appropriate care for acute cardiac events.

The tumor suppressor APC differentially regulates multiple ß-catenins through the function of axin and CKIα during C. elegans asymmetric stem cell divisions.

The APC tumor suppressor regulates diverse stem cell processes including gene regulation through Wnt-ß-catenin signaling and chromosome stability through microtubule interactions, but how the disparate functions of APC are controlled is not well understood. Acting as part of a Wnt-ß-catenin pathway that controls asymmetric cell division, Caenorhabditis elegans APC, APR-1, promotes asymmetric nuclear export of the ß-catenin WRM-1 by asymmetrically stabilizing microtubules. Wnt function also depends on a second ß-catenin, SYS-1, which binds to the C. elegans TCF POP-1 to activate gene expression. Here, we show that APR-1 regulates SYS-1 levels in asymmetric stem cell division, in addition to its known role in lowering nuclear levels of WRM-1. We demonstrate that SYS-1 is also negatively regulated by the C. elegans homolog of casein kinase 1α (CKIα), KIN-19. We show that KIN-19 restricts APR-1 localization, thereby regulating nuclear WRM-1. Finally, the polarity of APR-1 cortical localization is controlled by PRY-1 (C. elegans Axin), such that PRY-1 controls the polarity of both SYS-1 and WRM-1 asymmetries. We propose a model whereby Wnt signaling, through CKIα, regulates the function of two distinct pools of APC - one APC pool negatively regulates SYS-1, whereas the second pool stabilizes microtubules and promotes WRM-1 nuclear export.

A direct role for Fgf but not Wnt in otic placode induction.

Induction of the otic placode, which gives rise to all tissues comprising the inner ear, is a fundamental aspect of vertebrate development. A number of studies indicate that fibroblast growth factor (Fgf), especially Fgf3, is necessary and sufficient for otic induction. However, an alternative model proposes that Fgf must cooperate with Wnt8 to induce otic differentiation. Using a genetic approach in zebrafish, we tested the roles of Fgf3, Fgf8 and Wnt8. We demonstrate that localized misexpression of either Fgf3 or Fgf8 is sufficient to induce ectopic otic placodes and vesicles, even in embryos lacking Wnt8. Wnt8 is expressed in the hindbrain around the time of otic induction, but loss of Wnt8 merely delays expression of preotic markers and otic vesicles form eventually. The delay in otic induction correlates closely with delayed expression of fgf3 and fgf8 in the hindbrain. Localized misexpression of Wnt8 is insufficient to induce ectopic otic tissue. By contrast, global misexpression of Wnt8 causes development of supernumerary placodes/vesicles, but this reflects posteriorization of the neural plate and consequent expansion of the hindbrain expression domains of Fgf3 and Fgf8. Embryos that misexpress Wnt8 globally but are depleted for Fgf3 and Fgf8 produce no otic tissue. Finally, cells in the preotic ectoderm express Fgf (but not Wnt) reporter genes. Thus, preotic cells respond directly to Fgf but not Wnt8. We propose that Wnt8 serves to regulate timely expression of Fgf3 and Fgf8 in the hindbrain, and that Fgf from the hindbrain then acts directly on preplacodal cells to induce otic differentiation.

An expanded domain of fgf3 expression in the hindbrain of zebrafish valentino mutants results in mis-patterning of the otic vesicle.

The valentino (val) mutation in zebrafish perturbs hindbrain patterning and, as a secondary consequence, also alters development of the inner ear. We have examined the relationship between these defects and expression of fgf3 and fgf8 in the hindbrain. The otic vesicle in val/val mutants is smaller than normal, yet produces nearly twice the normal number of hair cells, and some hair cells are produced ectopically between the anterior and posterior maculae. Anterior markers pax5 and nkx5.1 are expressed in expanded domains that include the entire otic epithelium juxtaposed to the hindbrain, and the posterior marker zp23 is not expressed. In the mutant hindbrain, expression of fgf8 is normal, whereas the domain of fgf3 expression expands to include rhombomere 4 through rhombomere X (an aberrant segment that forms in lieu of rhombomeres 5 and 6). Depletion of fgf3 by injection of antisense morpholino (fgf3-MO) suppresses the ear patterning defects in val/val embryos: Excess and ectopic hair cells are eliminated, expression of anterior otic markers is reduced or ablated, and zp23 is expressed throughout the medial wall of the otic vesicle. By contrast, disruption of fgf8 does not suppress the val/val phenotype but instead interacts additively, indicating that these genes affect distinct developmental pathways. Thus, the inner ear defects observed in val/val mutants appear to result from ectopic expression of fgf3 in the hindbrain. These data also indicate that val normally represses fgf3 expression in r5 and r6, an interpretation further supported by the effects of misexpressing val in wild-type embryos. This is in sharp contrast to the mouse, in which fgf3 is normally expressed in r5 and r6 because of positive regulation by kreisler, the mouse ortholog of val. Implications for co-evolution of the hindbrain and inner ear are discussed.