CELL BIOLOGY OF THE NEURON Polarity ... - Tavernarakis Lab

Cell Biology of the Neuron: Polarity, Plasticity and Regeneration, Crete 2011
The Absence of TAG-1 Results in Perturbation of
Olfactory Bulb Organization and Function
George Bastakis, Maria Savvaki, Domna Karagogeos
IMBB FORTH/Medical school University of Crete
The immunoglobulin superfamily member TAG-1 plays an important role in
neurite outgrowth, fasciculation, neuronal migration and axon guidance during
development. The main projecting neurons of the olfactory bulb (OB) (mitral and
tufted cells) express TAG-1 during development but the exact role of this
molecule in olfactory system has not yet been investigated. The aim of the current
project is to elucidate the role of TAG-1 in the development and organization of
the olfactory system by using mice deficient for TAG-1 (Tag-1 ko) as a tool.
In adult and P0 (newborn) TAG-1 deficient mice we have observed significantly
decreased numbers of mitral cells in the olfactory bulb mitral cell layer (MCL)
compared to control animals. These results suggest that the defect in mitral cell
number can be attributed (i) to apoptosis (ii) to deficits during the development of
the olfactory bulb.
We examined the first case with IHC experiments in OB cryosections at various
developmental stages (E13,5-E18,5). We didn’t find any difference in cell
apoptosis (caspase3, TUNEL assays). These data indicate that the reduction of
mitral cells in adult mice was not an outcome of cell death. Subsequently, we
began searching the possible effect of TAG-1 absence that causes defects during
olfactory system development. By using a specific marker for projecting neuron
precursors (in OB) we found that there is no difference in their numbers between
Tag-1 ko and wt at E14,5, during their migration toward the MCL.
We further investigate the possible role of TAG-1 in mitral cell migration/
guidance with the use of a number of specific markers for projecting neurons,
guiding molecules and proliferation markers in-vitro and ex-vivo.
In addition behavioral analysis on Tag-1 deficient animals have shown no
olfactory learning impairments, but a probable olfactory memory deficit. We plan
to subject the animals in extensive olfactory behavioral trials, to elucidate the
importance of mitral cell layer organization in the olfactory system function.
Presented by: Bastakis, George
89
Poster No 007
Red Session