Hox genes are crucial for establishing segmental patterning of the vertebrate hindbrain into rhombomeres (r) and for the formation of segment boundaries (Lumsden and Krumlauf, 1996; Iimura and Pourquié, 2007).
While the hedgehog protein in Drosophila is a key player in the formation of segment polarity, its best characterized mammalian homologue Sonic hedgehog is involved in the development of the CNS, limbs, skeleton, and internal organs [ 16– 20].
This shows that the dermomyotome rescue is not dependent on the formation of segment boundaries, which is consistent with the observation that dermomyotome development is unaffected in segmentation mutants of the notch signaling pathway (data not shown) and suggests that lower levels of fss/tbx6 expression are sufficient for specification of central dermomyotome cells.
To test stretch dependence of NO formation, tissue segments were elongated by about 30% of initial length and the stretched and control segments homogenized.
As in Drosophila, Nv Krüppel (Kr) is expressed in a central domain, and Nv Kr is required for formation of segments T3 to A4 (Brent et al., 2007).
Accordingly, the assumed mechanism that cell oscillations slow with age [ 50, 51] cannot result in the formation of segments in our model.
Although abdominal segmental patterning has been extensively studied, the molecular mechanisms regulating cell division, migration, cell replacement and their interactions during formation of segments remain less well understood.
On the one hand, it gives rise to the cyclical waves that precede and promote the sequential formation of segments in the anterior GZ (Pueyo et al., 2008).
When flies develop without miR-965, they are mostly normal but have defects in the formation of segments in the abdomen.
> > > To detect the effects of aeration on aerenchyma formation, root segments were sectioned at 1 1.5 and 2 2.5 cm from the root tip.
