Figure 4. Defects in the Noncanonical Wnt/PCP Pathway Leading to Renal Cysts.
Correct orientation of the mitotic spindle and centrosomes with respect to the longitudinal axis of the tubule is critical for proper planar cell polarity (i.e., the orientation of an epithelial cell layer in three-dimensional space). Noncanonical Wnt/PCP signaling is involved in the regulation of planar cell polarity during renal tubular morphogenesis, when in 2-week-old rodents the tubules still elongate. In this model, if the mitotic spindle is maloriented, such as at an oblique angle to (or, to cite an extreme example, perpendicular to) the longitudinal orientation of tubule growth, the resulting structure would be a dilated tubule or cyst.