The Mother Centriole Plays an Instructive
Role in Defining Cell Geometry
ABSTRACT:
Centriole positioning is a key step in establishment and propagation of cell geometry, but the mechanism of this
positioning is unknown. The ability of pre-existing centrioles to induce formation of new centrioles at a defined angle
relative to themselves suggests they may have the capacity to transmit spatial information to their daughters. Using
three-dimensional computer-aided analysis of cell morphology in Chlamydomonas, we identify six genes required for
centriole positioning relative to overall cell polarity, four of which have known sequences. We show that the distal
portion of the centriole is critical for positioning, and that the centriole positions the nucleus rather than vice versa. We
obtain evidence that the daughter centriole is unable to respond to normal positioning cues and relies on the mother
for positional information. Our results represent a clear example of ‘‘cytotaxis’’ as defined by Sonneborn, and suggest
that centrioles can play a key function in propagation of cellular geometry from one generation to the next. The genes
documented here that are required for proper centriole positioning may represent a new class of ciliary disease genes,
defects in which would be expected to cause disorganized ciliary position and impaired function.
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