Are the molecular mechanisms of and neural structures supporting learning conserved in the larval and adult development stages in Drosophila? [abstract]

Abstract only availableFaculty Mentor: Dr. Troy Zars, Biological SciencesLearning describes the ability to change behavior based on experience. A memory is the stored form of those changes. Rather few molecules are known to be critical for memory formation. Even less is known about the relationship between those molecules and their temporal requirement through development. The rutabaga encoded type 1 adenylyl cyclase (rut-AC) is critical for both synaptic plasticity and memory formation in a number of species. Indeed, it has been proposed to be a molecular integratorí, responding synergistically to signals mediating the cue that is to be learned and the reinforcer. The rut-AC, thus, plays a central role in memory formation. In the Drosophila adult, the rut-AC has been found critical for every learning experiment in which it has been tested. And, the cellular site of action for the rut-AC has been determined for two learning paradigms. For learning olfactory cues, the rut-AC function is sufficient for memory formation in the Kenyon cells of the mushroom bodies. Drosophila larvae are capable of olfactory learning. To train larvae, one group is rewarded with fructose in the presence of odor A and not reinforced in the presence of a second odor B (A+/B). A complementary group receives opposite training (A/B+). During a memory test, animals are given a choice between A and B. Animals that received A+/B training show a higher preference for A than reciprocally trained animals. As all other parameters are equal between these groups, the odor preference difference is exclusively due to associative learning. The role of the rut-AC in memory formation is conserved through development. Wild-type Drosophila larvae trained as above perform significantly better than rut-AC mutant larvae. Thus, at least one of the molecules critical for synaptic plasticity has a conserved role in memory formation at multiple stages of development. Whether the Kenyon cells of the mushroom bodies are also sufficient for odor learning in the larval stage is the focus of continued experimentation.University of Missouri Research Board; Deutsche Forschungsgemeinschaf

Behavioral Analyses of Sugar Processing in Choice, Feeding, and Learning in Larval Drosophila

Gustatory stimuli have at least 2 kinds of function: They can support immediate, reflexive responses (such as substrate choice and feeding) and they can drive internal reinforcement. We provide behavioral analyses of these functions with respect to sweet taste in larval Drosophila. The idea is to use the dose–effect characteristics as behavioral “fingerprints” to dissociate reflexive and reinforcing functions. For glucose and trehalose, we uncover relatively weak preference. In contrast, for fructose and sucrose, preference responses are strong and the effects on feeding pronounced. Specifically, larvae are attracted to, and feeding is stimulated most strongly for, intermediate concentrations of either sugar: Using very high concentrations (4 M) results in weakened preference and suppression of feeding. In contrast to such an optimum function regarding choice and feeding, an asymptotic dose–effect function is found for reinforcement learning: Learning scores reach asymptote at 2 M and remain stable for a 4-M concentration. A similar parametric discrepancy between the reflexive (choice and feeding) and reinforcing function is also seen for sodium chloride (Niewalda T, Singhal S, Fiala A, Saumweber T, Wegener S, Gerber B, in preparation). We discuss whether these discrepancies are based either on inhibition from high-osmolarity sensors upon specifically the reflexive pathways or whether different sensory pathways, with different effective dose–response characteristics, may have preferential access to drive either reflex responses or modulatory neurons mediating internal reinforcement, respectively

Enhanced differentiation of human osteoblasts on Ti surfaces pre-treated with human whole blood

Early and effective integration of a metal implant into bone tissue is of crucial importance for its long-term stability. While different material properties including surface roughness and wettability but also initial blood-implant surface interaction are known to influence this osseointegration, implications of the latter process are still poorly understood. In this study, early interaction between blood and the implant surface and how this affects the mechanism of osseointegration were investigated. For this, blood coagulation on a micro-roughened hydrophobic titanium (Ti) surface (SLA-Hphob) and on a hydrophilic micro-roughened Ti surface with nanostructures (SLActive-HphilNS), as well as the effects of whole human blood pre-incubation of these two surfaces on the differentiation potential of primary human bone cells (HBC) was assessed. Interestingly, pre-incubation with blood resulted in a dense fibrin network over the entire surface on SLActive-HphilNS but only in single patches of fibrin and small isolated fiber complexes on SLA-Hphob. On SLActive-HphilNS, the number of HBCs attaching to the fibrin network was greatly increased and the cells displayed enhanced cell contact to the fibrin network. Notably, HBCs displayed increased expression of the osteogenic marker proteins alkaline phosphatase and collagen-I when cultivated on both surfaces upon blood pre-incubation. Additionally, blood pre-treatment promoted an earlier and enhanced mineralization of HBCs cultivated on SLActive-HphilNS compared to SLA-Hphob. The results presented in this study therefore suggest that blood pre-incubation of implant surfaces mimics a more physiological situation, eventually providing a more predictive in vitro model for the evaluation of novel bone implant surfaces

The lectin OS-9 delivers mutant neuroserpin to endoplasmic reticulum associated degradation in familial encephalopathy with neuroserpin inclusion bodies

A feature of neurodegenerative diseases is the intraneuronal accumulation of misfolded proteins. In familial encephalopathy with neuroserpin inclusion bodies (FENIB), mutations in neuroserpin lead to accumulation of neuroserpin polymers within the endoplasmic reticulum (ER) of neurons. Cell culture based studies have shown that ER-associated degradation (ERAD) is involved in clearance of mutant neuroserpin. Here, we investigate how mutant neuroserpin is delivered to ERAD using cell culture and a murine model of FENIB. We show that the ER-lectin OS-9 but not XTP3-B is involved in ERAD of mutant neuroserpin. OS-9 binds mutant neuroserpin and the removal of glycosylation sites leads to increased neuroserpin protein load whereas overexpression of OS-9 decreases mutant neuroserpin. In FENIB mice, OS-9 but not XTP3-B is differently expressed and impairment of ERAD by partial inhibition of the ubiquitin proteasome system leads to increased neuroserpin protein load. These findings show that OS-9 delivers mutant neuroserpin to ERAD by recognition of glycan side chains and provide the first in vivo proof of involvement of ERAD in degradation of mutant neuroserpin