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Virtually all renal cystic illnesses
are monogenic diseases (Table 470-1). A recent unifying theory of their pathophysiology
suggests that all gene products (“cystoproteins”)
that are mutated in cystic kidney diseases are expressed in primary
cilia, basal bodies, or centrosomes.1-4 Primary cilia are
antennalike cellular organelles produced by virtually every epithelial
cell type in the body. The structure and function of primary cilia
and basal bodies is delineated in eFig. 470.1.5,6 They
are important for perceiving extracellular cues, including photosensation,
mechanosensation, osmosensation, and olfactory sensation. Cilia
are assembled from basal bodies, which represent one of the two
centrosomes. Centrosomes and basal bodies contain the same protein
complexes that are part of the mitotic spindle in mitosis. These
protein complexes are crucial for planar cell polarity, or the orientation
of epithelial cells in three-dimensional space. Disruption of their
function leads to cyst development and to extrarenal defects that
have been summarized under the term ciliopathies.
In general, it seems that the pathogenesis of ciliopathies is based
on an inability of epithelial cells to sense or process extracellular
cues.7
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