Abstracts - Association for Chemoreception Sciences

#P222 POSTER SESSION V:
HUMAN TASTE PSYCHOPHYSICS;
OLFACTION RECEPTORS; TASTE DEVELOPMENT
#P223 POSTER SESSION V:
HUMAN TASTE PSYCHOPHYSICS;
OLFACTION RECEPTORS; TASTE DEVELOPMENT
Multiple Shh Signaling Centers in Embryo and Adult
Participate in Fungiform Papilla and Taste Bud Formation
and Maintenance
Hongxiang Liu 1 , Alex Ermilov 2 , Marina Grachtchouk 2 , Libo Li 1 ,
Deborah L Gumucio 3 , Andrezej A Dlugosz 2,3 , Charlotte M Mistretta 1
1
Department of Biologic and Materials Sciences, School of Dentistry,
University of Michigan Ann Arbor, MI, USA, 2 Department of
Dermatology, Medical School, University of Michigan Ann Arbor, MI,
USA, 3 Department of Cell and Developmental Biology, Medical School,
University of Michigan Ann Arbor, MI, USA
Fungiform papillae must contain long-lived sustaining cells
and short-lived maintaining cells that support development,
differentiation and maintenance of the lateral and apical papilla
epithelium and the specialized taste buds. Shh is a known
regulator of papilla development but details about locations
of ligand, target responding cells and transcriptional activators
for Shh signaling are not known. We used immunostaining, in
situ hybridization and reporters for Shh, Ptch1, Gli1 and Gli2-
expressing cells to identify proliferating and differentiating cells
in embryonic, postnatal and adult tongue, in papilla placodes,
fungiform papillae and/or taste bud cells that participate in
Shh signaling. Whereas there is a progressive restriction in
location of the Shh ligand, a receptive surround of Ptch1 and
Gli1 expression in responding cells is maintained in particular
epithelial and mesenchymal signaling centers throughout
papilla development and taste bud differentiation. From lineage
tracing, we know that Gli1-expressing cells and their progeny are
located in fungiform papilla basal cells, in perigemmal cells and
mesenchymal cells of the papilla core, and are progenitors of
taste cells. Further, using a doxycycline-regulated bitransgenic
GLI2* mouse, in a functional test of activated Shh signaling
in postnatal tongue epithelium, there is loss of filiform papilla
spines and loss of fungiform papillae and taste buds. Loss of
papilla organs is accompanied by proliferation in suprabasal
layers of the lingual epithelium. The synthesized data position
Shh signaling in multiple centers that are essential to placode
and papilla development, and to postnatal papilla and taste bud
differentiation and maintenance. Shh roles are most likely via
paracrine mechanisms, and engage epithelial/mesenchymal
interactions. Acknowledgements: NIH Grants NIDCD
DC000456 (CMM), NIDDK DK065850 (DLG), NCI CA087837
(AAD).
BDNF is Required for the Development of Adult Taste Bud
Number and Normal Behavioral Responses to Sour Stimuli
Abigail B. Menefee 1 , Robin F. Krimm 2
1
dupont Manual High School Louisville, KY, USA, 2 Dept. of
Anatomical Sciences and Neruobiology, Univeristy of Louisville Medical
School Louisville, KY, USA
Brain derived neurotrophic factor (BDNF) regulates gustatory
system development. Because BDNF removal is neonatal lethal,
the long-term effects of BDNF removal on the structure and
function of the adult gustatory system are unclear. To address
this issue we examined the adult taste system in conditional
Bdnf knockouts in which Bdnf expression is reduced to one-tenth
normal levels in the entire animal (Bdnf lox/lox ) and is completely
removed from the lingual epithelium (K14-Cre;Bdnf lox/lox ).
K14-Cre;Bdnf lox/lox mice had very few fungiform taste buds
remaining (11 ± 2) compared to wild type (52 ± 5, p ≤ 0.002)
or Bdnf lox/lox mice (42 ± 10; p ≤ 0.02). The K14-Cre;Bdnf lox/lox
circumvallate papillae contained 25% fewer taste buds than the
control genotypes (p ≤ 0.025). There was no difference in taste
bud number between wild type and Bdnf lox/lox , even though Bdnf
lox/lox
mice have substantially reduced Bdnf expression. Therefore,
as long as some BDNF remains, normal taste bud numbers
are maintained. Short-term lick rate tests of K14-Cre;Bdnf lox/
lox
, Bdnf lox/lox , and wild type mice were used to examine taste
function. Surprisingly, in spite of the large reduction in taste bud
number, there was no statistical difference among the genotypes
in lick rates to sucrose, quinine, and NaCl. This indicates that
normal behavioral taste responses can be maintained in mice
with few fungiform taste buds. However, K14-Cre;Bdnf lox/lox mice
have higher lick rates to citric acid at pH=3.2 (p ≤ 0.024) and
pH=2.8 (p ≤ 0.01) compared to wild type mice. This indicates
that removal of BDNF may cause a specific deficit in sour taste,
which cannot be explained simply by the loss of taste buds.
Acknowledgements: DC007176
#P224 POSTER SESSION V:
HUMAN TASTE PSYCHOPHYSICS;
OLFACTION RECEPTORS; TASTE DEVELOPMENT
Reorganization of Primary Afferent Terminal Fields in the
Mouse Brainstem Produced by Early Prenatal Dietary Sodium
Restriction
Chengsan Sun, David L Hill
University of Virginia/Psychology Charlottesville, VA, USA
Age-related decreases in terminal field volumes of the rat GSP,
CT, and IX nerves and their overlapping fields in the nucleus
of the solitary tract (NST) occur during normal development.
The processes involved in “pruning” the three terminal fields
can be altered significantly when rats are fed a sodium-restricted
diet from E3-E12. All terminal fields are relatively large during
early postnatal ages and thereafter fail to “prune”. Surprisingly,
many of the terminal fields in restricted rats expand after 35 days
POSTER PRESENTATIONS
Abstracts are printed as submitted by the author(s).
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