Meir, this is very interesting!  

Mag

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> [Original Message]
> From: Meir Weiss <[log in to unmask]>
> To: <[log in to unmask]>
> Date: 12/6/2006 10:34:22 AM
> Subject: WAYY COOL        EurekAlert! - Medicine/Health  Penn researchers
discover initial steps in the development of taste   Wnt protein required
for taste buds and wiring of taste signals to the brain
>
> http://www.eurekalert.org/bysubject/medicine.php
>
>  Public release date: 5-Dec-2006
> [ Print Article | E-mail Article | Close Window ]
>
> Contact: Karen Kreeger
> [log in to unmask]
> 215-349-5658
> University of Pennsylvania School of Medicine 
>
> Penn researchers discover initial steps in the development of taste
> Wnt protein required for taste buds and wiring of taste signals to the
brain
>
>
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>  
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>
> The pattern of active wnt protein (dark blue) follows the development of
taste
> papillae and buds in the tongue of a mouse.
>
> Click here for more information. 
>
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>  
> (PHILADELPHIA) -- Of the five senses, taste is one of the least
understood, but
> now researchers at the University of Pennsylvania School of Medicine have
come
> one step closer to understanding how the sense of taste develops. They
have
> pinpointed a molecular pathway that regulates the development of taste
buds.
> Using genetically engineered mice, they discovered that a signaling
pathway
> activated by small proteins called Wnts is required for initiating
taste-bud
> formation. They have also determined that Wnt proteins are required for
hooking
> up the wiring of taste signals to the brain. 
>
> Senior author Sarah E. Millar, PhD, Associate Professor in the
Departments of
> Dermatology and Cell and Developmental Biology, Penn postdoctoral fellow
Fei
> Liu, PhD, and colleagues report their findings in the most recent online
issue
> of Nature Genetics. "The developmental biology of taste is
underexplored," says
> Millar of her team's impetus for the study. 
>
> The researchers demonstrated that blocking the action of Wnt proteins in
surface
> cells of the developing tongue prevents taste-bud formation, while
stimulating
> Wnt activity causes the formation of excessive numbers of enlarged taste
> papillae that are able to attract taste-related nerve fibers. This study
> represents the first genetic analysis of taste-organ initiation in
mammals.
> While these studies were performed in mice, the researchers believe that
their
> findings will also hold true for understanding the basis of taste-bud
> development in humans.
>
> Taste buds are the sensory organs that transmit chemical stimuli from
food and
> other sources to nerve cells, which convey these signals to the taste
centers in
> the brain. Taste buds sit in the small bumps in the surface and sides of
the
> tongue called papillae. 
>
> The signaling pathway activated by Wnt proteins is critical to the
development
> of many organ systems, and its inappropriate activation causes human
diseases
> including colon cancer. In previous studies, Millar and colleagues have
shown
> that this pathway is essential for initiating the formation of hair
follicles
> and mammary glands in mice. 
>
> The sites of Wnt signaling are easily visualized in specially engineered
> transgenic mice, using an enzymatic assay. "We noticed in the tongue that
there
> was this beautiful pattern of blue spots that correspond to the
developing taste
> papillae," says Millar. "This connected the Wnt pathway to their
development." 
>
> In the present study, the researchers found that in mice in which the
actions of
> Wnt proteins were blocked, taste papilla buds completely failed to
develop.
> Conversely, in mice in which Wnt signaling was over activated, their
tongues
> were covered with many and large papillae and taste buds. 
>
> "Unlike most surface epithelial cells, taste buds have characteristics of
> neurons as well as skin. Like other types of epithelial cells they turn
over and
> regenerate, but they also express chemoreceptors and make synapses with
> neurons," explains Millar. The group studied how developing taste buds
become
> wired into the nervous system. In early tongue development, neurons enter
the
> tongue epithelium and make synapses with taste bud cells. This study
confirmed
> that taste buds produce signals that attract nerve fibers to them. When
> taste-bud development was prevented by blocking Wnt signaling, the nerve
fibers
> did not enter the tongue epithelium. 
>
> "They don't know where to go on their own," she says. 
>
> Millar also mentions that by now understanding the basis for the
initiation of
> taste-papilla formation, the evolution and difference between species in
the
> numbers and patterns of taste buds can be more fully explored. All
animals that
> taste have taste buds, but there are differences, for example humans have
more
> (around 200) taste papillae than mice, and they are arranged in a
different
> pattern.
>
> Future research directions will include determining whether Wnt signaling
is
> also important for the periodic regeneration of taste buds from taste-bud
stem
> cells that occurs throughout life in adult animals. Taste-bud
regeneration can
> be affected by chemotherapy, so understanding this process will have
important
> implications for patient care. 
>
> ###
> The research was supported by the National Institutes of Health. In
addition to
> Millar and Liu, co-authors on the paper are: Natalie Gallant, Seshamma T.
Reddy,
> and Thomas Andl, from Penn; Shoba Thirumangalathu and Linda Barlow from
the
> University of Colorado Health Sciences Center; Steven Yang and Andrzej A.
> Dlugosz from the University of Michigan; Cristi L. Stoick-Cooper and
Randall T.
> Moon from the Howard Hughes Medical Institute and University of
Washington; and
> Makoto M. Taketo from Kyoto University.
>
> For this release and related image, go to: http://www.uphs.upenn.edu/news/
>
> PENN Medicine is a $2.9 billion enterprise dedicated to the related
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>
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>
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hospital;
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and
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>
>
>
>
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