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Poster Full Abstracts - Neurophysiology and Behavior
Poster board number is above title. The first author is the presenter
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various pesticides. Despite the widespread use of such pesticides, issues regarding drug specificity and resistance continue to pose serious problems in
regions that rely on pesticides for crop protection and prevention against disease. We are characterizing three novel Cys-loop LGIC subunits; CG7589,
CG6927 and CG11340 in
Drosophila melanogaster
to determine their potential as pesticide targets. These genes are of particular interest because they are
specific to arthropods and do not possess any orthologs in vertebrate systems (Dent, 2006). Consequently, pesticides that target channels formed by these
genes are predicted to be safe and have low risk for off-target effects. Electrophysiological tests indicate that CG11340 can form a functional homomeric
channel while CG7589 and CG6927 can form a heteromeric channel. We also generated loss of function alleles for all three genes and data suggest that
mutations in CG7589 and CG11340 exhibit lethal phenotypes. The expression profiles of all three channel subunits are unconventional in that they are
seemingly absent from neural and muscular tissue and instead, appear to be localized in secretory tissues. CG7589 and CG11340 are expressed in the midgut
and Malpighian tubules - tissues involved in ion regulation and renal function - and CG6927 appears to be expressed in tracheal tissue and salivary glands.
Furthermore, consistent with the CG11340 expression data, preliminary findings indicate that CG11340 mutants are sensitive to osmotic stress. Based on the
divergence of these genes from other Cys-loop LGIC subunits as well as the lethal phenotypes associated with the corresponding mutants, these putative
subunits may provide a promising target for a novel class of highly selective and efficient pesticides.
628A
The role of glia in axonal degeneration.
Bibhudatta Mishra, Catherine A Collins. Molecular,Cellular and Developmental Biology, University of Michigan,
Ann Abor, MI.
Purpose of statement
Axonal degeneration occurs after injury, as well as in neuropathies and neurodegenerative disorders. However the cellular
mechanism for axonal degeneration is poorly understood. The aim of our study is to understand the role of glia in axonal degeneration after injury,
particularly the role of glia which function in insulating axons in peripheral nerves, and the role of electrical activity in degeneration.
Methods used
We
used a nerve crush assay (Xiong X et al., 2010) to study Wallerian degeneration of Drosophila motoneurons after injury, and screened mutations known to
disrupt specific subtypes and functions of glia. We genetically manipulated the electrical activity of a small subset of motoneurons by the m12-Gal4 driver
line (Ritzenthaler et al., 2000) to over-express either a dominant negative mutation in the shaker K channel to hyperexcite neurons, or an inward rectifying K
channel (Kir2.1) to silence neurons. We also used a conditional allele of the voltage gated Na channel, para-ts, to silence neurons acutely at different time
points either before, during, or after injury.
Summary of results
We found that disruption of the moody gene cause a dramatic delay in the initiation of
axonal degeneration after injury. moody encodes an orphan GPCR whose function is required for regulation of the blood brain barrier (BBB). One function
of this barrier is to insulate neurons from high concentrations of potassium in the hemolymph. Consistent with an important role for this insulation,
electrically silenced neurons do not degenerate, while hyperexcitable neurons degenerate faster. Timing of action studies with para-ts suggest that electrical
activity in the distal stump is an important factor in the initiation of the degeneration process.
Conclusion
Our results suggest that the disrupted septate
junction leads to delayed axon degeneration, and altered electrical activity in neurons affects their resiliency to axonal degeneration. We propose that the
electrical activity of neurons is an important factor in the axonal degeneration process.
629B
Probing the regulatory mechanisms of AKH cell excitability.
Rebecca J Perry, Jason T Braco, Erik C Johnson. Department of Biology, Wake Forest
University, Winston-Salem, NC.
The mechanisms of how organimsms maintain metabolic homeostasis in light of dynamic nutrient availability is not completely understood. In Drosophila,
the adipokinetic hormone (AKH) is a principal hormone that functions in this process. AKH signaling regulates energy levels through the direct mobilization
of trehalose during low hemolymph sugar. Adipokinetic hormone is required for starvation-induced hyperactivity, an adaptive behavior that assists in
foraging. In order to better understand AKH signaling, we are conducting a genome-wide RNAi based screen targeting different ion channels that may
regulate AKH cell physiology. We evaluated the consequences of RNAi expression in AKH cells on AKH related phenotypes, specifically lifespan and
locomotion during starvation. From this initial behavioral screen, we identified the channel encoding the TASK6 potassium channel as a candidate AKH
regulatory element. Expression of the TASK6 RNAi in AKH cells leads to lengthened lifespan during starvation. Additionally, there were observable
changes in starvation-induced hyperactivity. We are in the process of confirming TASK6 expression in AKH neuroendocrine cells through single-cell RT-
PCR. We will also report preliminary experiments on AKH cell activation in a TASK6 mutant background and report other findings from the genome-wide
RNAi screen.
630C
CREB results in memory enhancement for a conditioned place preference & courtship suppression task in Drosophila melanogaster.
Eugenia
Friedman
1
, Toshihiro Kitamoto
2
, Jerry Yin
3
. 1) Neuroscience Training Program, University of Wisconsin-Madison, Madison, WI; 2) Dept. of
Anesthesiology, University of Iowa, Iowa City, Iowa; 3) Dept. of Genetics, University of Wisconsin-Madison, Madison, WI.
It is generally agreed that activation of cAMP-responsive element binding protein (CREB) is required for long-term memory (LTM) formation. There are
however conflicting results regarding memory enhancement produced from the dCREB2a “activator” isoform. Using a transgenic N-terminally truncated
dCREB2a (807), we show that dCREB2a enhances memory in both conditioned courtship suppression and conditioned place preference, a novel paradigm
developed in the lab. Conditioned courtship suppression is a well-established learning and memory task that exploits natural mating behaviors. Briefly, male
807 and matching controls were paired with premated females for 5 hours. On the following day only 807 flies exhibited courtship suppression compared to
the controls indicating that 807 enhanced memory. To date there is no behavioral paradigm designed for flies measuring a reward based associative memory
at the single animal level. We have developed an assay for Drosophila, comparable to the conditioned place preference used in rodents. In this protocol a
single fly is exposed to visual stimuli differentiating one arm of a t-maze from another. Ethanol is presented in one arm over 3 trials inducing associative
memory formation between a visual cue and ethanol. One day following training individual flies are tested for place preference (time in arm previously
associated with ethanol versus the non-ethanol arm), indicative of a reward based memory. We tested this paradigm using 807 and an 807 null mutant,
ATG2. Similarly to courtship suppression results, 807 enhances place preference for the ethanol associated arm 20 hours following training compared to
ATG2 controls. These results suggest overlapping roles for dCREB2 in the genetic pathways of both types of associative memories, and supports prior
evidence for the role of CREB in Drosophila LTM.