First published online August 25, 2006
Development 133, 1805e (2006)
© The Company of Biologists Limited
Mammary development: no Hedgehog required
Hedgehog (Hh) signalling is essential for the development of many
vertebrate epidermal appendages, including hair and teeth. Another epidermal
appendage that shares a common origin is the mammary gland. But, as Hatsell
and Cowin now report, positive Hh signalling is absent throughout the
embryonic and postnatal development of mouse mammary glands (see
p. 3661). In mammals,
three Gli transcription factors act downstream of Hh: the activator Gli2
induces the expression of Gli1, which antagonizes the repressor activity of
Gli3. The researchers show that although Gli2 and Gli3 are
expressed during embryonic mammary development, Hh target genes are not
expressed. Furthermore, whereas mammary gland development is normal in mice
that lack Gli1 or Gli2, two pairs of mammary buds are
missing in Gli3xt/xt mouse embryos, which do not make
Gli3. Misactivation of the Hh pathway by targeted expression of Gli1
in Gli3xt/+ mice also induces mammary bud loss. Thus, the
researchers conclude, Gli3-mediated repression of Hh signalling is required
for normal embryonic mammary development.
Related articles in Development:
- Gli3-mediated repression of Hedgehog targets is required for normal mammary development
- Sarah J. Hatsell and Pamela Cowin
Development 2006 133: 3661-3670.
[Abstract]
[Full Text]
