Biomedical Engineering Reference
In-Depth Information
Single slice
3D Rendered image
E15.5
Phospho-histone H3
;
cytokeratin
Figure 8.3 Orientation of cell division in the prospective medullary collecting duct cells
is disrupted in Wnt7b mutants. The cell division plane (red line in the schematic draw-
ing) tends to bias toward perpendicular to the longitudinal axis of the prospective med-
ullary collecting ducts (the arrow in the schematic drawing) in wild-type kidney, which
favors elongation of the collecting ducts. In contrast, the plane of cell division tends to
be parallel to the longitudinal axis of the prospective medullary collecting ducts in
Wnt7b mutant kidneys, which favors an increase in the diameter of collecting ducts.
Wnt11
,
Wnt4
, and to a lesser extent,
Wnt5a
mRNAs (
Yu et al., 2009
). All
three of theseWnts are thought to primarily signal through the noncanonical
pathway. Thus, it appears that the regulation of PCP by
Wnt7b
within the
context of the kidney collecting ducts may be indirect. A reasonable model
based on the data is that
Wnt7b
, signaling through
b
-catenin, activates the
expression of noncanonical ligands within the interstitium that signal back
to the collecting ducts to regulate PCP and oriented cell division, thus driv-
ing medullary collecting duct extension.
4.3.2 Wnt9b
Like
Wnt7b
,
Wnt9b
is also expressed in the embryonic collecting ducts
although Wnt9b expression extends more toward the branching tips. Mice
carrying a germline null mutation of
Wnt9b
do not form renal vesicles or
maintain their cap mesenchyme (
Carroll, Park, Hayashi, Majumdar, &
