Abstracts - Association for Chemoreception Sciences

maintenance; demonstrate a contribution of Shh responding,
Gli1 labeled progeny to taste bud cells and cells of the papilla;
and present distinctive effects of activating Shh transcription
factors in adult tongue. Defined proliferation niches of active
Shh signaling suggest that epithelium and mesenchyme harbor
multiple stem and progenitor cell compartments. In sum, Shh
has roles to form and maintain fungiform papillae and taste
buds, most likely via stage-specific autocrine and/or paracrine
signaling, with epithelial/mesenchymal interactions. Neural
crest cells also contribute to developing and postnatal lingual
epithelium and mesenchyme, including taste papillae and taste
buds. Further, Shh signaling in neural crest cells participates in
patterning the tongue. In all, cells originating in several lingual
tissue areas contribute to the stem and progenitor compartments
that are active in forming and maintaining taste buds and
papillae. Supported by NIH NIDCD Grant DC000456.
#24 SYMPOSIUM:
STEM AND PROGENITOR CELLS FOR
TASTE BUDS — DEVELOPMENT AND RENEWAL
In search of adult taste stem cells
Karen Yee 1 , Yan Li 1 , Kevin Redding 1 , Ken Iwatsuki 2 ,
Robert Margolskee 1 , Peihua Jiang 1
1
Monell Chemical Senses Center, 3500 Market Street, Philadelphia,
PA, USA, 2 Institute for Innovation, Ajinomoto Co., Inc.,
Kawasaki-ku, Kawasaki, Japan
Recently, a great deal of progress has been made in identifying
reliable markers for adult stem cells for many regenerative
mammalian tissues. For instance, Lgr5 (leucine-rich repeatcontaining
G-protein coupled receptor 5) is a bona fide marker
for adult stem cells in intestine, stomach, and hair follicle. In
the small intestine of mice the Polycomb group protein Bmi1
marks another population of stem cells distinct from the Lgr5+
stem cells. Taste epithelium also regenerates constantly, yet the
identity of adult taste stem cells remains elusive. In this study we
set out to determine if Lgr5 and Bmi1 mark adult taste stem/
progenitor cells. We found that Lgr5 is strongly expressed in
cells at the bottom of trench areas at the base of circumvallate
and foliate taste papillae and weakly expressed in the basal area
of taste buds and that Lgr5-expressing cells in posterior tongue
are a subset of K14-positive epithelial cells. Lineage-tracing
experiments using an inducible Lgr5-Cre knock-in allele in
combination with Rosa26-LacZ and Rosa26-tdTomato reporter
strains showed that Lgr5-expressing cells gave rise to taste cells,
perigemmal cells, along with self-renewing cells at the bottom
of trench areas at the base of circumvallate and foliate papillae.
Moreover, using subtype-specific taste markers, we found that
Lgr5-expressing cell progeny include all three major types of
adult taste cells. Our results indicate that Lgr5 may mark adult
taste stem cells in the posterior portion of the tongue. In contrast,
our lineage tracing experiments using Bmi1-Cre; Rosa26-
LacZ showed that Bmi1 does not mark adult taste stem cells.
Acknowledgements: This work was supported by NIH grants
DC0101842 (P.J.), DK081421 (R.F.M.), DC003055 (R.F.M.),
P30DC011735 (R.F.M) and a grant from the Commonwealth of
Pennsylvania Department of Health (P.J.)
#25 SYMPOSIUM:
STEM AND PROGENITOR CELLS FOR
TASTE BUDS — DEVELOPMENT AND RENEWAL
Cell types in adult taste buds: distinct longevities and origins
Nirupa Chaudhari
Department of Physiology and Biophysics, and Program in
Neurosciences, University of Miami Miller School of Medicine,
Miami, FL, USA
Mammalian taste buds are repopulated throughout adult life
with new cells that are born in the basal epithelium immediately
surrounding them. Taste buds contain several molecularly and
functionally distinct classes of cells, but it is unclear whether
each class is derived from a separate progenitor cell pool, and
has similar longevity. Using high resolution confocal microscopy,
and 4-color fluorescent labeling, we examined whether the
previously described average life-time of taste bud cells applies to
each of the cell types that make up the taste bud. After a single
EdU injection to label newly born cells, we fitted exponential
decay curves to the disappearance of labeled nuclei from each
cell type. While sweet-, bitter- and umami-sensing Type 2 cells
displayed a half-life of ≈8 days, sour-sensing neuron-like Type
3 cells were much longer-lived, with a half-life of over 22 days.
Curiously, many post-mitotic cells had a prolonged quiescence
inside taste buds before differentiating into mature taste cells.
We also evaluated whether all taste cell types arise from a
common pool of progenitor cells using lineage-tracing analyses
in adult KERATIN14-cre/ERT;Rosa26-YFP mice. Non-taste
keratinocytes were produced rapidly (within 2 days) from K14+
progenitors; Type I glial-like cells became YFP+ ≈10 days after
induction, whereas Type II cells contained YFP+ cells only after
≈20 days. In stark contrast, Type III cells did not noticeably
acquire the YFP lineage-label even 60 days after induction. Thus,
while most cells of the taste bud arise from K14+ progenitors,
the dynamics of their appearance suggests that several separate
progenitor cell pools replenish adult taste buds during normal
renewal. Supported by NIH/NIDCD R01DC6308
#26 SYMPOSIUM:
STEM AND PROGENITOR CELLS FOR
TASTE BUDS — DEVELOPMENT AND RENEWAL
Development and regeneration of the inner ear: Control of
cell division and differentiation of sensory progenitors
Neil Segil
Division of Cell Biology and Genetics, House Research Institute;
and Department of Cell and Neurobiology, University of
Southern California.
Loss of the sensory hair cells of the inner ear is the major cause
of deafness and balance disorders. Hair cells are extremely
sensitive to various environmental stressors such as ototoxic
drugs noise, and aging. In mammals, the failure to regenerate
these cells is complete, making hair cell loss a major global health
problem. In contrast to the failure of regeneration in mammals,
non-mammalian vertebrates can efficiently regenerate sensory
hair cells through a combination of direct transdifferentiation
ORAL ABSTRACTS
Abstracts are printed as submitted by the author(s).
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