These cells, forming the procambium zone, arise by divisions oriented at right angles to the axis and may form a complete cylinder; generally, however, interruptions occur, the segments being related to the uppermost leaf primordia.
The wing achieves its final form through spatially patterned cell divisions, oriented cell divisions, physical constraints on directional growth by an actin network between the wing veins, and by patterned cell death.
FAMAp:amiRNA-RBR GCs underwent inappropriate extra divisions oriented transverse to the long axis of the cells, while other epidermal cells were not affected, confirming a direct requirement for RBR in GCs and confirming phenotypes reported using different amiRNAs directed against RBR (Lee et al., 2014a).
During zebrafish gastrulation (Concha and Adams, 1998), cell division is oriented contrary to the long axis and is regulated by a non-canonical Wnt pathway, which may override physical parameter-mediated spindle positioning (Gong et al., 2004).
These divisions are oriented parallel to the wing disc epithelium and hence the AMPs form a monolayer of proliferating cells that remain in contact with the disc epithelium.
These asymmetric divisions are oriented obliquely to the wing disc surface such that the self-renewing daughter cells remain in contact with the disc epithelium while the postmitotic daughters become located in the more distal layer of non-replicating myoblasts.
After cell division, hepatocytes orient themselves in the direction of the closest sinusoid, a process named "hepatocyte-sinusoid alignment" (HSA), which is essential for the restoration of liver microarchitecture.
In zebrafish, hair cell orientation is also a consequence of two events: 1) the oriented division of progenitor cells to give rise to a sibling pair of cells, with one of each pair lying on opposite sides of an axis and 2) the orientation of the hair bundles ([29]).
On the other hand, if cell division planes are oriented regularly or the expansion of individual cells is directional, the tissue can assume any of a number of shapes.
