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Poster Full Abstracts - Neural Development
Poster board number is above title. The first author is the presenter
315
tolloid-like), as an essential gene required for clustering of iGluRs at the NMJ. Neto co-localizes with the iGluRs at the PSDs, in puncta juxtaposing the
active zones. neto loss-of-function phenotypes parallel the loss-of-function defects described for iGluR complexes. The defects in neto mutants are
effectively rescued by muscle specific expression of neto transgenes. Neto clustering at the Drosophila NMJ coincides with and is dependent on iGluRs. Our
studies reveal that Drosophila Neto is a novel, essential component of the iGluR complexes and is required for iGluRs clustering, organization of PSDs and
synapse functionality.
689B
Drosophila
Mitofusin regulates function and development of the neuromuscular junction.
Hector Sandoval
1
, Chi-Kuang Yao
2
, Kuchuan Chen
1,3
, Yong
Qi Lin
6
, Taraka Donti
1
, Manish Jaiswal
1
, Vafa Bayat
1,3,4
, Ke Zhang
5
, Claire Hauter
6
, Bo Xiong
1,3
, Wu-Lin Charng
1,3
, Shinya Yamamoto
1,3
, Brett Graham
1
,
Hugo Bellen
1,3,6
. 1) Human and Molecular Genetics, Baylor College of Medicine, Houston, TX 77030; 2) Institute of Biological Cehmistry, Academia
Sinica, Nankang,Taipei 115, Taiwan; 3) Program in Development Biology, Baylor College of Medicine, Houston, TX 77030; 4) Medical Scientist Training
Program, Baylor College of Medicine, Houston, TX 77030; 5) Structural and Computational Biology and Molecular Biophysics, Baylor College of
Medicine, Houston, TX 77030; 6) Howard Hughes Medical Institute, Baylor College of Medicine, Houston, TX 77030.
Mitochondria are dynamic organelles that continually undergo fusion, fission, and trafficking. These cell biological processes control mitochondrial shape,
number, size, distribution, and physiology. Neurons utilize mitochondrial dynamics to provide the high demand for energy at synaptic terminals. In a
forward genetic screen designed to isolate mutations that cause neurodegenerative phenotypes, we identified 7 mutations in
Marf
(Mitochondrial Associated
Regulatory Factor). Marf encodes the
Drosophila
homolog of mammalian mitofusins, proteins that promote mitochondrial fusion. Loss of function
mutations in the human Marf homologue cause Charcot-Marie-Tooth type 2A, an axonal peripheral sensorimotor neuropathy primarily affecting lower and
extremities. To better understand the neuronal processes that are affected by the loss of Marf, we assessed some neuronal phenotypes. In the eye, mutations
in
Marf
lead to a reduced amplitude of the electroretinogram (ERG) recordings and a degeneration of the photoreceptors and their terminals. At the NMJs,
loss of Marf causes a severe loss of presynaptic mitochondria, and neurotransmitter release is impaired during prolonged stimulation.
Marf
mutants also
exhibit an altered NMJ synapse morphology. We are currently testing several hypothesis related to how the functional and developmental defects arise at the
NMJ.
690C
Liquid facets (Lqf) plays novel roles in BMP signaling and retrograde transport.
Phillip Vanlandingham, Lerin Luckett-Chastain, Taylor Fore, Hong
Bao, Bing Zhang. Dept. of Zoology, University of Oklahoma, Norman, OK.
Maintenance of synaptic growth and function depends on the interaction of cell signaling and intracellular trafficking. Activation of presynaptic BMP
receptors leads to phosphorylation of the downstream effector MAD, and translocation to the nucleus where pMAD regulates expression of genes important
for synaptic growth and activity. Little is known about the mechanisms through which BMP signaling and pMAD trafficking are linked at the synapse. We
have previously shown that Lqf, the Drosophila homolog of epsin, positively controls synaptic growth and function as loss of Lqf decreases synaptic
transmission and NMJ size, while neuronal overexpression dramatically increases NMJ growth. Here we test whether Lqf mediates growth and function in a
BMP-dependent manner. Using immunofluorescence, we observe higher levels of pMAD at the NMJ in
lqf
mutants relative to control, whereas Lqf
overexpression decreases pMAD levels at the NMJ. This result contrasts with mutants such as
nwk
that show higher levels of pMAD at the NMJ correspond
to increases in synaptic growth. Therefore, we examined pMAD in the nucleus of motoneurons where we observe no change in
lqf
mutants relative to
control, but a dramatic increase in
nwk
mutants. As a result, we predict Lqf-dependent retrograde transport of pMAD to motoneuron nuclei is necessary for
BMP growth signaling. Consistent with a defect in retrograde transport of pMAD, lqf genetically interacts with lis1, whose mutations phenocopy the NMJ
physiological and pMAD defects observed in
lqf
mutants. We show that pMAD is regulated downstream of Wit as pMAD levels at the NMJ decrease below
control levels in
lqf, wit
double mutants. Further, Lqf interacts with Wit as shown by immunoprecipitation, and Wit accumulates at the plasma membrane
upon overexpression of Lqf, where Lqf may negatively regulate the receptor. Hence, our results reveal novel dual roles for Lqf in BMP signaling: Lqf
negatively regulates BMP receptor activation, and positively promotes pMAD translocation to the nucleus. Supported by NIH/NINDS grant (RO1NS06878).
691A
Phosphorylation of Hts at the MARCKS domain inhibits its ability to regulate Dlg postsynaptic targeting during neuromuscular junction
development.
Simon Wang
1
, Amy Tsai
2
, Charles Krieger
2
, Nicholas Harden
1
. 1) Department of Molecular Biology and Biochemistry, Simon Fraser
University, Burnaby, British Columbia, Canada; 2) Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British
Columbia, Canada.
Mammalian adducins are a group of cytoskeletal proteins that regulate actin filaments in several ways such as cross-linking with spectrin and capping of
the barbed ends. These roles are inhibited via phosphorylation of the myristoylated alanine-rich C kinase substrate (MARCKS) domain by Protein kinase C
(PKC). We have previously shown that phospho-adducin levels are elevated in spinal cord tissue taken from patients who have died from Amyotrophic
Lateral Sclerosis, a neurological disease that causes degeneration of motor neurons. To explore further the significance of phospho-adducin in the nervous
system, we decided to study
Drosophila
adducin which is encoded by
hu-li tai shao
(
hts
). To do this, we created a phospho-mimetic
hts
transgene where the
putative target site of PKC in the MARCKS domain was altered from a serine to an aspartic acid. We provide evidence that expression of a wild-type
hts
transgene in the muscle disrupts the localization of Discs large (Dlg) at the postsynaptic membrane of larval neuromuscular junctions (NMJs). In contrast,
disruption of Dlg localization was greatly reduced when the phospho-mimetic
hts
transgene was expressed. Other studies have shown that Dlg postsynaptic
targeting is regulated by Partitioning-defective 1 (PAR-1). We show that expression of wild-type
hts
, but not phospho-mimetic
hts
, can elevate PAR-1
protein levels in the muscle causing increased phosphorylation of Dlg. We conclude that Hts is a signalling-responsive component of the cytoskeleton that
contributes to synaptic plasticity during NMJ development, at least in part by regulating Dlg postsynaptic localization through PAR-1 dependent
phosphorylation.
692B
Drosophila
Cyfip regulates synaptic growth and endocytosis by suppressing F-actin assembly.
Lu Zhao, Dan Wang, Qifu Wang, Yongqing Zhang.