Biomedical Engineering Reference
In-Depth Information
A
Oriented cell division
B
Directed intercalation
C
Multicellular rosette formation and resolution
Rosette
formation
Ver tex
Resolution
Figure 8.2 Processes regulating tubule elongation. (A) Oriented cell division leads to
lengthening of the tubule, while the diameter stays the same. (B) Directed intercalation
leads to the tubule elongating while it also becomes thinner. (C) Multicellular rosette
formation and resolution (adapted from
Zallen & Blankenship, 2008
) describe the
changes in cell morphology and adhesiveness that result in a transient rosette with a
vertex forming. The rosette resolves resulting in the tubule becoming longer and thin-
ner. Only oriented cell division has been demonstrated in the kidney. Panels (B) and (C)
require live imaging to confirm.
elongation perpendicular to the axis of extension (a form of PCP) (
Bertet,
Sulak, & Lecuit, 2004; Nikolaidou & Barrett, 2005; Shih & Keller, 1992;
Skoglund & Keller, 2010; Wallingford et al., 2000; Wang et al., 2005;
Zallen & Blankenship, 2008
). Kidney epithelial cells show such
morphology. However, kidney epithelia also form multicellular rosettes
(C.M. Karner & T.C. Carroll, unpublished observations). Unfortunately,
the issue of which (if any) type of movement is taking place during tubule
formation can only be conclusively demonstrated using live imaging,
which has not been accomplished in a vertebrate as of yet. However,
CE-like movements would explain how a proliferating epithelium with
randomly oriented cell division does not increase its diameter.
Cell intercalation/rearrangement appears to be a conserved mechanism
in regulating renal
tubule size. During Drosophila Malpighian tubule
