Role of transmembrane protein strabismus in motor neuron migration in the zebrafish hindbrain

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 25, 2010).The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Dissertation advisor: Dr. Anand Chandrasekhar.Vita.Ph. D. University of Missouri--Columbia 2008.Nervous system development involves extensive cell migration, causing immature neurons to move from proliferative zones to specific locations to generate functional circuits. Defective in neuronal migration can cause severe anomalies including mental retardation and learning disabilities. Therefore, it is important to understand the molecular mechanisms underlying neuronal migration. We use zebrafish as a model to study one such migration. In the zebrafish and mouse hindbrain, Facial Branchiomotor Neurons (FBMNs), which mediate jaw and facial movements in mammals, migrate caudally (tangentially) from rhombomere 4 (r4) into r6 and r7. The transmembrane protein Strabismus (Stbm) is a component of the non-canonical Wnt/PCP pathway and is necessary for the normal migration of FBMNs. To understand the mechanisms by which stbm regulates neuronal migration, I sought (1) to identify the cell types where stbm function is required for FBMN migration (2) to analyze the various domains of Stbm and their requirement for FBMN migration and (3) to analyze other genes interacting with stbm to regulate FBMN migration. Previous analyses showed that stbm is expressed ubiquitously, and function non-cell autonomously during FBMN migration. Expression analysis of stbm and its interacting partner prickle1a (pk1a) raised the possibility that stbm and pk1a may function in non-neural tissues such as the paraxial mesoderm or endoderm to regulate FBMN migration. FBMN migration occurs normally in embryos lacking endoderm suggesting that endoderm-expressed stbm is not necessary for FBMN migration. Targeted transplantation of stbm-deficient cells into the mesoderm of wild-type host embryos does not affect FBMN migration indicating that mesoderm-expressed stbm is also not essential for FBMN migration. However, transplanted wild-type cells generating ventral neural tube cells including floorplate were able to rescue FBMN migration in stbm [superscript -slash-] mutants. Conversely, transplanted stbm-deficient cells generating ventral neural tube cells such as floorplate were able to block FBMN migration in wild-type zebrafish embryos, suggesting strongly that stbm expression in the floorplate is necessary and sufficient for FBMN migration. Strabismus (Stbm) is predicted to be a four pass transmembrane protein with N- and C- terminal cytoplasmic domains, and a PDZ domain binding motif at the C-terminus. To identify regions of Stbm that are essential for mediating FBMN migration, we tested the abilities of the cytosolic N- & C- terminal fragment to rescue migration in the stbm [superscript -slash-] mutants. Surprisingly, both constructs rescued defective FBMN migration, suggesting that both N- and C- terminal domains of Stbm can independently facilitate downstream events mediating FBMN migration in zebrafish hindbrain. Genetic mosaic analyses have indicated that stbm functions in the environment especially in the ventral neural tube cells such as floorplate to regulate FBMN migration. This result suggests that stbm expressed outside motor neurons genetically interact with other genes expressed in FBMNs and the ventral neural tube to mediate FBMN migration. To test this hypothesis, we examined the roles of Transient axonal glycoprotein-1 (Tag-1) and Laminin [alpha] 1, which respectively encode cell adhesion and extracellular matrix protein, during FBMN migration. Tag-1 is expressed in FBMNs and its knockdown using antisense morpholinos leads to loss of FBMN migration. It genetically interacts with stbm to regulate FBMN migration. Laminin [alpha] 1 (lama1) also interact genetically with stbm to regulate FBMN migration. These results indicate that FBMN expressed tag-1 may be interacting with stbm in adjacent cells and lama1 to regulate FBMN migration.Includes bibliographical reference

Food Waste Recycling and Education to Promote Sustainability at Georgia Southern University and the Community

Proposed by Dr. Padmini Shankar, Department of Health Sciences and Kinesiology, Dr. Evans Afriyie-Gyawu, Department of Biostatistics, Epidemiology, and Environmental Health Sciences and Dr. Vinoth Sittaramane, Department of Biology. ($40,000.00

The cell adhesion molecule Tag1, transmembrane protein Stbm/Vangl2, and Lamininα1 exhibit genetic interactions during migration of facial branchiomotor neurons in zebrafish

AbstractInteractions between a neuron and its environment play a major role in neuronal migration. We show here that the cell adhesion molecule Transient Axonal Glycoprotein (Tag1) is necessary for the migration of the facial branchiomotor neurons (FBMNs) in the zebrafish hindbrain. In tag1 morphant embryos, FBMN migration is specifically blocked, with no effect on organization or patterning of other hindbrain neurons. Furthermore, using suboptimal morpholino doses and genetic mutants, we found that tag1, lamininα1 (lama1) and stbm, which encodes a transmembrane protein Vangl2, exhibit pairwise genetic interactions for FBMN migration. Using time-lapse analyses, we found that FBMNs are affected similarly in all three single morphant embryos, with an inability to extend protrusions in a specific direction, and resulting in the failure of caudal migration. These data suggest that tag1, lama1 and vangl2 participate in a common mechanism that integrates signaling between the FBMN and its environment to regulate migration

Transient axonal glycoprotein-1 (TAG-1) and laminin-α1 regulate dynamic growth cone behaviors and initial axon direction in vivo

<p>Abstract</p> <p>Background</p> <p>How axon guidance signals regulate growth cone behavior and guidance decisions in the complex <it>in vivo </it>environment of the central nervous system is not well understood. We have taken advantage of the unique features of the zebrafish embryo to visualize dynamic growth cone behaviors and analyze guidance mechanisms of axons emerging from a central brain nucleus <it>in vivo</it>.</p> <p>Results</p> <p>We investigated axons of the nucleus of the medial longitudinal fascicle (nucMLF), which are the first axons to extend in the zebrafish midbrain. Using <it>in vivo </it>time-lapse imaging, we show that both positive axon-axon interactions and guidance by surrounding tissue control initial nucMLF axon guidance. We further show that two guidance molecules, transient axonal glycoprotein-1 (TAG-1) and laminin-α1, are essential for the initial directional extension of nucMLF axons and their subsequent convergence into a tight fascicle. Fixed tissue analysis shows that TAG-1 knockdown causes errors in nucMLF axon pathfinding similar to those seen in a laminin-α1 mutant. However, <it>in vivo </it>time-lapse imaging reveals that while some defects in dynamic growth cone behavior are similar, there are also defects unique to the loss of each gene. Loss of either TAG-1 or laminin-α1 causes nucMLF axons to extend into surrounding tissue in incorrect directions and reduces axonal growth rate, resulting in stunted nucMLF axons that fail to extend beyond the hindbrain. However, defects in axon-axon interactions were found only after TAG-1 knockdown, while defects in initial nucMLF axon polarity and excessive branching of nucMLF axons occurred only in laminin-α1 mutants.</p> <p>Conclusion</p> <p>These results demonstrate how two guidance cues, TAG-1 and laminin-α1, influence the behavior of growth cones during axon pathfinding <it>in vivo</it>. Our data suggest that TAG-1 functions to allow growth cones to sense environmental cues and mediates positive axon-axon interactions. Laminin-α1 does not regulate axon-axon interactions, but does influence neuronal polarity and directional guidance.</p

The mouse Wnt/PCP protein Vangl2 is necessary for migration of facial branchiomotor neurons, and functions independently of Dishevelled

AbstractDuring development, facial branchiomotor (FBM) neurons, which innervate muscles in the vertebrate head, migrate caudally and radially within the brainstem to form a motor nucleus at the pial surface. Several components of the Wnt/planar cell polarity (PCP) pathway, including the transmembrane protein Vangl2, regulate caudal migration of FBM neurons in zebrafish, but their roles in neuronal migration in mouse have not been investigated in detail. Therefore, we analyzed FBM neuron migration in mouse looptail (Lp) mutants, in which Vangl2 is inactivated. In Vangl2Lp/+ and Vangl2 Lp/Lp embryos, FBM neurons failed to migrate caudally from rhombomere (r) 4 into r6. Although caudal migration was largely blocked, many FBM neurons underwent normal radial migration to the pial surface of the neural tube. In addition, hindbrain patterning and FBM progenitor specification were intact, and FBM neurons did not transfate into other non-migratory neuron types, indicating a specific effect on caudal migration.Since loss-of-function in some zebrafish Wnt/PCP genes does not affect caudal migration of FBM neurons, we tested whether this was also the case in mouse. Embryos null for Ptk7, a regulator of PCP signaling, had severe defects in caudal migration of FBM neurons. However, FBM neurons migrated normally in Dishevelled (Dvl) 1/2 double mutants, and in zebrafish embryos with disrupted Dvl signaling, suggesting that Dvl function is essentially dispensable for FBM neuron caudal migration. Consistent with this, loss of Dvl2 function in Vangl2Lp/+ embryos did not exacerbate the Vangl2Lp/+ neuronal migration phenotype. These data indicate that caudal migration of FBM neurons is regulated by multiple components of the Wnt/PCP pathway, but, importantly, may not require Dishevelled function. Interestingly, genetic-interaction experiments suggest that rostral FBM neuron migration, which is normally suppressed, depends upon Dvl function

Factors Associated With Local Health Departments’ Engagement in Food Safety Initiatives for People in the Communities Across United States

Presented at American Public Health Association (APHA) Annual Conference. Background: Foodborne illnesses in the United States result in about 3,000 deaths and costs more than $15.6 billion each year. Objective: This study aims to generate practice-relevant evidence associated with the engagement of local health departments (LDHs) in food safety and policy issues. Methods: Data from the 2019 National Profile of Local Health Departments Survey of all 2,459 LHDs in the United States was analyzed. The census design (rather than the sample) resulted in a response rate of 61%. Descriptive, chi-square and logistic regression analyses were performed to model all multiple dichotomous variables. Results: During the year before the 2019 survey, 75.8% of LHDs directly provided nutrition services, 40.7% provided food processing inspection, 78.9% performed food safety inspections, 78.3% provided food safety education, and 48.4% engaged in policymaking and advocacy concerning food safety. The bivariate results showed statistically significant associations of LHD characteristics with these food safety activities as well as the policy engagement. Multivariable analysis showed that odds of LHDs directly providing preventive nutrition services were 20 times if the LHD had a nutritionist on staff (Adjusted Odds Ratio or AOR=20.0; Confidence Interval, CI=12.4-32.2). Other LHDs characteristics significantly associated with the provision of nutrition services (at pConclusion: LHDs play a critical role in ensuring safe food for Americans, and eliminating health inequities in food safety. Adequate funding and competent staffing are essential for LHDs to utilize evidence-based practices and engage in policymaking and advocacy concerning food safety

The Detrimental Impact of the COVID-19 Crisis on Health Equity and Social Determinants of Health

The World Economic Forum reports the COVID-19 pandemic could push half a billion people in the world into poverty and financially impact millions more due to the 20% drop in income caused by the impending recession.1 This contagion is expected to exacerbate the inequities and disparities in health outcomes for older adults, persons in poor living environments, and residents of resource-poor rural communities across the United States. For the poor and disenfranchised, many social determinants of health (SDoH) are expected to worsen during the COVID-19 (the disease caused by SARS-CoV-2) pandemic and in its aftermath, namely, employment, housing, food, education, and health care. Public health professionals and policy makers need to proactively work with community partners to influence policies and other relevant sectors to ensure that health inequities do not intensify for the most vulnerable in our communities. The far-reaching impact of the COVID-19 pandemic is already being felt among population subgroups as a function of poverty, whether it is due to structural racial injustice, an inability to treat underlying chronic conditions due to increased health care burden and clinic closures, patients\u27 lack of access to critically needed health care, or a product of long-standing social injustices manifested mainly through food insecurity or job and income losses

Sewage Monitoring in Rural Communities: A Powerful Strategy for COVID-19 Surveillance

To contain the COVID-19 outbreak and mobilize mitigation efforts, public health surveillance relies heavily on individual COVID-19 test results. A shortage of supplies, equipment, facilities, public health professionals, and trained laboratory personnel creates challenges for detection and management of the outbreak, especially in rural and underserved communities. Clinical testing might not be feasible or cost-effective for monitoring the community spread of COVID-19, especially in rural areas. Robust surveillance approaches with a greater coverage potential are needed for developing effective public health strategies during the current pandemic. Findings from recent studies show that the SARS-CoV-2 virus can be detected in stool samples collected from hospitalized individuals, which has led to a new surveillance approach for testing sewage to detect the presence of SARS-CoV-2 RNA. This approach offers a tremendous potential for real-time screening of community spread of COVID-19. This month’s cover highlights a guest commentary, “Sewage Monitoring in Rural Communities: A Powerful Strategy for COVID-19 Surveillance,” that explores the merit, limitations, and challenges of implementing sewage monitoring methods in rural parts of the U.S. to protect public health and inform policy and decision making

Ensuring Food Safety for Americans: The Role of Local Health Departments

(1) Background: Several agencies in the United States play a primary role in ensuring food safety, yet foodborne illnesses result in about 3000 deaths and cost more than USD 15.6 billion each year. The study objectives included analyzing local health departments&rsquo; (LHDs) level of engagement in food safety and other related services, and LHDs&rsquo; characteristics associated with those services. (2) Methods: We used data from 1496 LHDs that participated in the 2019 National Profile of Local Health Departments Survey, administered to all 2459 LHDs in the United States. Logistic regression analyses were performed to model multiple dichotomous variables. (3) Results: An estimated 78.9% of LHDs performed food safety inspections, 78.3% provided food safety education, 40.7% provided food processing inspections, and 48.4% engaged in policy and advocacy. The odds for LHDs to directly provide preventive nutrition services were 20 times higher if the LHDs had one or more nutritionists on staff (Adjusted Odds Ratio or AOR = 20.0; Confidence Interval, CI = 12.4&ndash;32.2) compared with LHDs with no nutritionists. Other LHD characteristics significantly associated with the provision of nutrition services (p &lt; 0.05) included population size, state governance (rather than local), and LHD having at least one registered, licensed, practical, or vocational nurse. The odds of providing food processing services were lower for locally governed than state-governed LHDs (AOR = 0.5; CI = 0.4&ndash;0.7). The odds of performing food safety inspections varied by LHD&rsquo;s population size, whether a nutritionist was on staff, whether it was state-governed (vs. locally), and whether it completed a community health assessment (CHA) within 5 years. (4) Conclusions: LHDs play a critical role in ensuring safe food for Americans, yet variations exist in their performance based on their specific characteristics. Adequate funding and a competent workforce are essential for LHDs to utilize evidence-based practices and engage in policymaking and advocacy concerning food safety