First published online March 9, 2007
Development 134, 705e (2007)
© The Company of Biologists Limited
Limb development: into the mix
How cells in the developing limb are patterned to form distal or proximal
limb structures is a contentious issue. One current model - the
prespecification model - proposes that cells are specified into all regions
along the proximodistal axis at an early stage. Now, in contrast to these
findings, Tamura and co-workers show that, while the proximal chick limb
region is regionalised at an early stage of limb development, the distal
region is maintained in an unregionalised condition and consists of
intermingling cells (see
p.1397). These
intermingling cells can adopt either a zeugopod (more proximal) or autopod
(distal) fate, as shown by the analysis of HOXA11 and HOXA13 expression. Later
in development, a clearer boundary can be seen between the autopod and
zeugopod regions, but some cell mixing still occurs within the distal autopod
region. This study redefines our understanding of cell specification within
the developing limb and suggests that each limb structure is likely to be
regionalised in a proximodistal direction.

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Related articles in Development:
- Specification of cell fate along the proximal-distal axis in the developing chick limb bud
- Kosei Sato, Yutaka Koizumi, Masanori Takahashi, Atsushi Kuroiwa, and Koji Tamura
Development 2007 134: 1397-1406.
[Abstract]
[Full Text]