Abstracts - Association for Chemoreception Sciences

P O S T E R S
#P219 POSTER SESSION V:
CENTRAL OLFACTION; CHEMOSENSORY
PSYCHOPHYSICS & CLINICAL STUDIES
Expression and function of Rap1gap2 in the developing
olfactory system
Benjamin A Sadrian, Qizhi Gong
University of California, Davis Davis, CA, USA
Regulation of Rap1 signaling plays important roles in cortical
circuit formation and synapse remodeling. To investigate the
function of Rap1 regulation in the development of the olfactory
system, we cloned and characterized a novel Rap1GAP, also
known as Garnl4. Garnl4 is 95% homologous in amino acid
sequence to human RAP1GAP2. GTPase Activating Proteins
(GAPs) catalyze the inactivation of small GTPases, thereby
regulating their multidimensional signaling roles. We validated
that Garnl4 is the mouse Rap1gap2 by comparing active Rap1
levels with and without Garnl4 overexpression in a heterologous
cell system. Rap1gap2 is exclusively expressed in the central
nervous system as detected by western blotting analysis.
Immunohistochemistry shows Rap1gap2 expression in olfactory
sensory neurons at the olfactory epithelium as well as in OSN
axons, which persists to the nerve terminals in the glomerular
layer of the olfactory bulb. During development, Rap1GAP2
signal is detectable in all glomeruli at P0; however, by P14 a
mosaic glomerular expression pattern emerges and persists into
adulthood. We have characterized Rap1GAP2 function in a
neuroblastoma differentiation assay. Rap1gap2 overexpression
inhibits Neuro2A neurite outgrowth. In contrast, Neuro2a cells
exhibit exuberant outgrowth with Rap1 overexpression, which is
eliminated by co-overexpression of Rap1gap2. The function of
Rap1GAP2 in the regulation of olfactory axon growth and
branching is currently being investigated. Acknowledgements:
Supported by: NIH DC06015, NSF IBN0324769, and the NIH
T32 Doctoral Training Grant
#P220 POSTER SESSION V:
CENTRAL OLFACTION; CHEMOSENSORY
PSYCHOPHYSICS & CLINICAL STUDIES
Dishevelled-1 in mouse olfactory system development
Diego J Rodriguez-Gil 1 , Wilbur Hu 1 , Charles A Greer 1,2
1
Yale University, School of Medicine Dept Neurosurgery
New Haven, CT, USA, 2 Yale University, School of Medicine Dept
Neurobiology New Haven, CT, USA
Olfactory sensory neuron (OSN) axons navigate from the
olfactory epithelium (OE) to the olfactory bulb (OB), where they
coalesce into specific glomeruli. Odor receptor (ORs), a variety of
trophic and repulsive molecules, and OSN functional activity
have been strongly implicated in the coalescence and targeting of
OSN axons. Formerly known as morphogens, there is increasing
evidence that Wnt molecules, signaling through Frizzled receptors
(Fz), contribute in a variety of processes, including cell
proliferation, migration and the development of neuronal circuits.
We previously demonstrated that Fz-1 and Fz-3 are expressed in
OSNs from early embryonic stages, and that they present specific
expression patterns during development and in adult mice. In
order to characterize putative Wnt/Fz signaling mechanisms, we
began by characterizing the expression pattern of Dishevelled-1
(Dvl-1). Dishevelled plays a central role in many of the proposed
Wnt/Fz signaling mechanisms. Expression of Dvl-1 in the OE
begins early in development and is restricted to the most dorsal
zone of the OE. Dvl-1 expression exceeds that of NQO1, a
marker for OSNs located dorsally. OSNs expressing the OR M72,
which is a dorsal Class II OR, coexpress Dvl-1. In the OB Dvl-1
is restricted to OSN axons, where it has a punctate distribution
and appears later than embryonic day 13. Axons expressing Dvl-1
overlap with NQO1, but also with some dorsal OCAMglomeruli
that are NQO1 negative. Rostal-caudal analyses
showed that expression in the OB is lateral in the most rostral part
and then shifts to medial-dorsal in the most caudal portion. Both
the punctate axonal distribution as well as the relatively late onset
of expression in axons suggest a possible role of Dvl-1 in synapse
formation/stabilization of OSN in the OB. Acknowledgements:
Support In Part By: NIH DC00210, DC006972 and DC006291
to CAG.
#P221 POSTER SESSION V:
CENTRAL OLFACTION; CHEMOSENSORY
PSYCHOPHYSICS & CLINICAL STUDIES
MMP-2 expression in the olfactory bulb is associated with
neuronal reinnervation
Stephen R Bakos, Richard M Costanzo
Virginia Commonwealth University Richmond, VA, USA
We previously reported that matrix metalloproteinase-2 (MMP-2),
an enzyme that degrades the extracellular matrix, is elevated in the
olfactory bulb of mice 7 days following olfactory nerve
transection (NTx), when newly regenerated axons begin to
innervate the bulb. To determine if MMP-2 is associated with the
regenerated axons, we inserted a piece of Teflon between the
cribriform plate and bulb following nerve transection to block the
axons (TB-NTx). We then compared olfactory bulb expression
levels of MMP-2 and olfactory marker protein (OMP) following
NTx and TB-NTx at different recovery time points using Western
blot. Following NTx, OMP expression decreased by day 3 and
remained low for a week, demonstrating neuronal degeneration.
By day 10, OMP expression returned to control levels, indicating
neuronal regeneration and bulb reinnervation. With the Teflon
blocker, OMP levels decreased but failed to return to control
levels, indicating successful blockage of the regenerated axons.
In contrast to the significant increased in MMP-2 observed
following NTx, levels in TB-NTx mice remained low. This
finding demonstrates the increased expression of MMP-2 is
dependent on the regenerated axons innervating the olfactory
bulb. These axons may utilize MMP-2 to penetrate through the
extracellular matrix to reestablish connections in the olfactory
bulb. Acknowledgements: Supported by R01 DC000165 (RMC)
from the National Institute of Deafness and Other
Communication Disorders
100 | AChemS Abstracts 2010 Abstracts are printed as submitted by the author(s)