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Trachemys scripta immunoglobulin-rich fractions hydrolyze viral DNA in vitro
Title
Trachemys scripta immunoglobulin-rich fractions hydrolyze viral DNA in vitro.
Creator
Lloyd, Brandon N., Graduate College
Date Issued
2010-04-09
PURL
http://purl.flvc.org/fcla/dt/3176817
Format
Document (PDF)
RanBP9 Plays a Critical Role in Neonatal Brain Development in Mice
Title
RanBP9 Plays a Critical Role in Neonatal Brain Development in Mice.
Creator
Palavicini, Juan Pablo, Lloyd, Brandon N., Hayes, Crystal D., Bianchi, Elisabetta, Kang, David E., Dawson-Scully, Ken, Lakshmana, Madepalli K., Okazawa, Hitoshi
Abstract/Description
RanBP9 is known to act as a scaffolding protein bringing together a variety of cell surface receptors and intracellular targets thereby regulating functions as diverse as neurite and axonal outgrowth, cell morphology, cell proliferation, myelination, gonad development, myofibrillogenesis and migration of neuronal precursors. Though RanBP9 is ubiquitously expressed in all tissues, brain is one of the organs with the highest expression levels of RanBP9. In the neurons, RanBP9 is localized...
Show moreRanBP9 is known to act as a scaffolding protein bringing together a variety of cell surface receptors and intracellular targets thereby regulating functions as diverse as neurite and axonal outgrowth, cell morphology, cell proliferation, myelination, gonad development, myofibrillogenesis and migration of neuronal precursors. Though RanBP9 is ubiquitously expressed in all tissues, brain is one of the organs with the highest expression levels of RanBP9. In the neurons, RanBP9 is localized mostly in the cytoplasm but also in the neurites and dendritic processes. We recently demonstrated that RanBP9 plays pathogenic role in Alzheimer’s disease. To understand the role of RanBP9 in the brain, here we generated RanBP9 null mice by genetrap based strategy. Most of Ran-/- mice die neonatally due to defects in the brain growth and development. The major defects include smaller cortical plate (CP), robustly enlarged lateral ventricles (LV) and reduced volume of hippocampus (HI). The lethal phenotype is due to a suckling defect as evidenced by lack of milk in the stomachs even several hours after parturition. The complex somatosensory system which is required for a behavior such as suckling appears to be compromised in Ran-/- mice due to under developed CP. Most importantly, RanBP9 phenotype is similar to ERK1/2 double knockout and the neural cell adhesion receptor, L1CAM knockout mice. Both ERK1 and L1CAM interact with RanBP9. Thus, RanBP9 appears to control brain growth and development through signaling mechanisms involving ERK1 and L1CAM receptor.
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Date Issued
2013-06-26
PURL
http://purl.flvc.org/fau/fd/FAUIR000081
Format
Citation
Synaptic Rearrangements and the Role of Netrin-Frazzled Signaling in Shaping the Drosophila Giant Fiber Circuit
Title
Synaptic Rearrangements and the Role of Netrin-Frazzled Signaling in Shaping the Drosophila Giant Fiber Circuit.
Creator
Lloyd, Brandon N., Murphey, Rodney K., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Biological Sciences
Abstract/Description
In the developing CNS, presynaptic neurons often have exuberant overgrowth and form excess (and overlapping) postsynaptic connections. Importantly, these excess connections are refined during circuit maturation so that only the appropriate connections remain. This synaptic rearrangement phenomenon has been studied extensively in vertebrates but many of those models involve complex neuronal circuits with multiple presynaptic inputs and postsynaptic outputs. Using a simple escape circuit in...
Show moreIn the developing CNS, presynaptic neurons often have exuberant overgrowth and form excess (and overlapping) postsynaptic connections. Importantly, these excess connections are refined during circuit maturation so that only the appropriate connections remain. This synaptic rearrangement phenomenon has been studied extensively in vertebrates but many of those models involve complex neuronal circuits with multiple presynaptic inputs and postsynaptic outputs. Using a simple escape circuit in Drosophila melanogaster (the giant fiber circuit), we developed tools that enabled us to study the molecular development of this circuit; which consists of a bilaterally symmetrical pair of presynaptic interneurons and postsynaptic motorneurons. In the adult circuit, each presynaptic interneuron (giant fiber) forms a single connection with the ipsilateral, postsynaptic motorneuron (TTMn). Using new tools that we developed we labeled both giant fibers throughout their development and saw that these neurons overgrew their targets and formed overlapping connections. As the circuit matured, giant fibers pruned their terminals and refined their connectivity such that only a single postsynaptic connection remained with the ipsilateral target. Furthermore, if we ablated one of the two giant fibers during development in wildtype animals, the remaining giant fiber often retained excess connections with the contralateral target that persisted into adulthood. After demonstrating that the giant fiber circuit was suitable to study synaptic rearrangement, we investigated two proteins that might mediate this process. First, we were able to prevent giant fibers from refining their connectivity by knocking out highwire, a ubiquitin ligase that prevented pruning. Second, we investigated whether overexpressing Netrin (or Frazzled), part of a canonical axon guidance system, would affect the refinement of giant fiber connectivity. We found that overexpressing Netrin (or Frazzled) pre- & postsynaptically resulted in some giant fibers forming or retaining excess connections, while exclusively presynaptic (or postsynaptic) expression of either protein had no effect. We further showed that by simultaneously reducing (Slit-Robo) midline repulsion and elevating Netrin (or Frazzled) pre- & postsynaptically, we significantly enhanced the proportion of giant fibers that formed excess connections. Our findings suggest that Netrin-Frazzled and Slit-Robo signaling play a significant role in refining synaptic circuits and shaping giant fiber circuit connectivity.
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Date Issued
2016
PURL
http://purl.flvc.org/fau/fd/FA00004758, http://purl.flvc.org/fau/fd/FA00004758
Subject Headings
Drosophila melanogaster--Cytogenetics., Genetic transcription., Transcription factors., Cellular signal transduction., Cellular control mechanisms., Cell receptors.
Format
Document (PDF)