doi: 10.1242/10.1242/jcs.00204
Anomalous centriole configurations are detected in Drosophila wing disc cells upon Cdk1 inactivation
Smruti J. Vidwans1,
Mei Lie Wong2 and
Patrick H. O'Farrell1,*
1 Department of Biochemistry and Biophysics, University of California —
San Francisco, 513 Parnassus Avenue, Box 0448, San Francisco, CA 94143,
USA
2 Howard Hughes Medical Institute, Department of Biochemistry and Biophysics,
University of California — San Francisco, 513 Parnassus Avenue, Box
0448, San Francisco, CA 94143, USA
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Fig. 1. Wing discs from sevelen (wild-type) larvae or Cdk1ts larvae.
Eggs were collected and aged to the late second instar larval stage at
18°C. Larvae were then shifted to 30°C for 2 days, after which they
were fixed. Discs were dissected and stained for DNA with the dye,
bis-benzidine (Hoechst). Wing discs in which Cdk1 has been inactivated are,
typically, smaller in size compared with similarly treated sevelen discs and
have fewer cells that are bigger than normal. Bar, 25 µm.
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Fig. 2. Centriole length is misregulated upon inactivation of Cdk1. In all cases,
the mother centriole is on the left and the daughter on the right.
Furthermore, we have oriented images so that mothers in longitudinal section
have their long axes running top-bottom and daughters in longitudinal section
have their long axes facing left-right. Since the section is thinner than the
centriole, a longitudinal section through a centriole appears as a pair of
parallel lines (representing the walls of the centriole). A centriole in
cross-section appears as a circle (Vidwans
et al., 1999 ). The pairs of pictures in A, D and E are adjacent
sections from a series. (A,B) Control centrioles from sevelen wing discs
incubated at 30°C for 2 days. (C,D,E) Centrioles from Cdk1-inactivated
wing disc cells. (A) Both the mother and the daughter in this centriole pair
are in longitudinal section. Note that the daughter is shorter than its mother
(compare the mother in the left section to daughter in the right). (B) Both
the mother and the daughter centrioles are in longitudinal section, with the
daughter shorter than its mother. (C) A longitudinal mother-daughter centriole
pair with a long mother. Compare the length of this mother to those in A and
B. (D) A mother in cross-section with a long daughter in longitudinal section.
Compare the length of this mother to that in A and B. (E) A longitudinal
centriole pair with long mother and daughter. The daughter is longer than its
mother. Bar, 100 nm.
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Fig. 3. Distribution of lengths of mother and daughter centrioles from sevelen and
Cdk1ts wing discs incubated at 30°C for 2 days. The x-axis is
centriole length (measured in nm) and the y-axis is the number of centrioles
at any given length. Note that the distribution of daughter centrioles from
wild-type discs varies between 46 and 93 nm, while the corresponding
distribution from ts discs varies between 46 and 162 nm. The wider
distribution of daughter centriole lengths in ts discs is reflected in the
higher average: 114 nm compared with 70 nm in wild-type. The distribution of
mother centrioles from ts discs is also broader than wild-type (105 to 184 nm
in ts discs compared with 93 to 139 nm in wild-type). The average mother
centriole length in ts discs is 134 nm compared with 115 nm in wild-type.
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Fig. 4. Mother centrioles with two daughters. Three examples of mother centrioles
with two daughters. Each triplet is shown in two consecutive serial sections
with a schematic to orient the reader. (A) A mother centriole (in the center)
that is slightly angled with two longitudinal daughters, one to the left and
the other to the right. (B) A mother in cross-section with two daughters, both
in longitudinal section, one to the left and one (seen only in the section at
the right) at the top. (C) A mother in cross-section with two longitudinal
daughters, one to the right and the other to the left. Note that one of the
daughters in each triplet is always longer than the other, suggesting that the
two daughters were assembled at different times. Furthermore, note that the
differences in the angle between the two daughter centrioles suggest that the
initiation of a second daughter can occur at a variety of positions with
respect to the first daughter. Bar, 100 nm.
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Fig. 5. Examples of mother, daughter and granddaughter triplet centrioles. Each
triplet is shown in two consecutive serial sections with a schematic on the
right to orient the reader. All the centriole triplets are oriented with the
mother on the left, the daughter to the right and the granddaughter to the top
or bottom. To accomplish this orientation, adjustments were made in Adobe
PhotoShop, some of which appear as discontinuities within the images (D,E).
Note that mother and daughter in B are not quite orthogonal, while the
arrangement in D and E appears to be orthogonal. Note that if mother daughter
orientation is fixed, the granddaughter can emerge from different faces of the
daughter, suggesting that the asymmetry is not programmed by the preceding
generation of centriole. Bar, 100 nm.
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© The Company of Biologists Ltd 2003
