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Poster Full Abstracts - Neural Development
Poster board number is above title. The first author is the presenter
309
neuron central dendrite development; a Dscam function in self-recognition and avoidance, and second, a Dscam function in stabilizing immature filopodia so
they may mature into stable dendrites. Mechanisms and functional consequences for flight behavior are currently under investigation.
664A
NMNAT protects against hypoxia-induced dendrite degeneration.
Yuhui Wen, Grace Zhai, Michael Kim. Molecular and Cellular Pharmacology,
University of Miami, Miller School of Medicine, Miami, FL.
The proper maintenance of dendritic arbors is important for neuronal connectivity and function. Loss of dendrites induced by hypoxia is one of the
pathological hallmarks of brain injury after stroke. Dendritic fields of Drosophila class IV dendritic arborization (da) sensory neurons provide a unique
system to investigate the mechanisms important for dendrite maintenance. We previously found that the NAD synthase Nicotinamide mononucleotide
adenylyl transferase (NMNAT) is required for the proper maintenance of class IV dendrites during larval development. Here, we show that NMNAT is also
important for maintaining dendritic integrity under hypoxia. We found that wild-type flies under anoxic conditions (extreme condition of hypoxia, 0.1% O2)
exhibited slightly reduced dendritic branching, but no signs of degeneration. However, flies heterozygous for a loss-of-function mutation in nmnat showed
reduced dendritic branching along with severe dendrite degeneration under the same anoxic conditions. These results suggest that NMNAT maintains
dendritic integrity under anoxia in a dose-dependent manner. We further found that knockdown of genes with important roles in autophagy suppress dendrite
degeneration phenotypes in nmnat heterozygotes under anoxia. Our findings suggest that NMNAT protects against autophagy-related processes that
contribute to dendrite degeneration in response to hypoxic conditions.
665B
RNAi screen to identify genes involved in retinal basal glia (RBG) cells in Drosophila.
Yen-Ching Chang
1,2
, Y. Henry Sun
1,2
. 1) Institute of Molecular
Biology, Academia Sinica, Taipei, Taiwan, Republic of China; 2) Department of Life sciences and Institute of Genome sciences, National Yang-Ming
University, Taipei, Taipei, Taiwan.
During the process of the eye development, elaborate photoreceptor-glia interaction is required for the formation of mature visual system. Retinal basal
glial (RBG) cells proliferate and migrate from optic stalk to the eye disc after the differentiation of photoreceptor cells. When they migrate into the eye disc,
they provide a guidance cues for photoreceptor axon projection, and they differentiate into wrapping glial cells responsible for axonal insulation. Several
important genes have been discovered to elucidate the relationship between glia cells and photoreceptor cells. These genes can be separated into two groups:
one is the intrinsic factor (acting within RBG) like Ras, the other are the extrinsic factors (derived from other cells but affecting RBG) such as FGF ligands
for migration and differentiation. However, the mechanism regulating the cellular development and interaction with cells in eye disc remains unclear.
Additional molecular players need to be identified. We will screen for genes functioning in RBGs to affect their migration, distribution, differentiation and
proliferation. We drove UAS-RNAi expression in RBG using
repo
-Gal4, and monitored the fluorescent-labeled cellular morphology and pattern of RBG.
Among 139 RNAi lines screened, we found 21 genes with morphological defects. Some of them are cell cycle regulated genes played roles in RBG
development. The genes affecting proliferation/migration/differentiation have been further analyzed by immunostaining and other genetic approaches.
666C
Study of Cell Lineage in Drosophila Retinal Basal Glia.
Yu Fen Huang
1,2
, Y. Henry Sun
1,2
. 1) Institute of Molecular Biology, Academia Sinica, Taipei,
Taiwan; 2) Department of Life Science and Institute of Genome Science, National Yang-Ming University, Taipei, Taiwan.
Glial cells play important roles in neuronal development and function. The retinal basal glia (RBG) is a subset of glial cell that originates in the optic stalk
in second instar of
Drosophila
. RBG cells start to migrate into the eye disc as photoreceptor cells (R cell) begin to differentiate. The presence of RBG cells
in eye discs is essential for R cell axons to enter the optic stalk. Three main classes of RBG cells have been identified including carpet glia (CG), surface glia
(SG), and wrapping glia (WG). According to the “sequential differentiation model” proposed by Silies et al. (
J. Neurosci.
27:13130-9), surface glia located
at the basal side migrates forward along the carpet glia. Once they reach the anterior margin of carpet glia and contact the neuron, these migratory glia starts
to differentiate into wrapping glia and wrap around R cell axons. The two large nuclei CG cells have extensive membrane and are regard as an insulator
between SG and WG. To test this model, I am using Twin-spot MARCM (Yu et al.,
Nat. Neurosci
12, 947-953) to trace the cell lineage of RBG. My results
suggested that there are independent lineage decisions for SG and WG.
667A
Degeneration of optic lamina caused by defective endocytic function in glial cells.
Yuan-Ming Lee
1,2
, Y. Henry Sun
1,2
. 1) Inst Molecular Biology,
Academia Sinica, Taipei, Taiwan; 2) Inst Genomic Science, National Yang-Ming University, Taipei, Taiwan.
The visual system is composed of neurons and glial cells. In the optic lamina and medulla, there are also several distinct groups of glial cells. These are
known to play a role in photoreceptor axonal projection and maintain the physiological function of the lamina monopolar neurons. We are interested in the
function of glias in the adult visual system. By blocking the endocytic pathway by expressing the temperature-sensitive dominant-negative dynamin (shits1)
in glia, the degenerative vacuoles formed in the optic lamina. Our analyses also suggest that the vacuoles are formed cell-autonomously by the epithelial and
marginal glia in the optic lamina in MARCM experiment. The visual synaptic transmission was abolished in phototaxis and in ERG assays. The vacuolized
lamina was rescued by the coexpression of dTOR but not anti-apoptotic p35. Therefore the endocytic function may be required for the glia to survive by
inhibit caspase-independent or autophagy. Molecular definition of the autophagy features in degeneration neuropile is still studying.
668B
Number Matching Between Ommatidia and Retinal Basal Glial Cells (RBGs) during
Drosophila
Eye Development.
Par B. Pun
1,2
, Yi Henry Sun
1,2
. 1)
Molecular and Cell Biology, Taiwan International Graduate Program, Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan; 2) Graduate
Institute of Life Science, National Defense Medical Center, Taipei, Taiwan.
Glial cells are important for nervous system in maintaining homeostasis of neurons, guiding neuronal axon projection and regulating axon fasciculation.
The compound eye of
Drosophila
consists of around 750 ommatidia along with glial cells. These glial cells, located at the basal part of eye disc, called the
retinal basal glia (RBG) cells,originate from optic stalk in second instar of larva and migrate into eye disc along with photoreceptor cells differentiation.