Biology Reference
In-Depth Information
in identifying the separate functions mediated by a centrosomal protein (Gopala-
krishnan et al.
2011
).
Third: it is possible to biochemically isolate centrosomes and centrosomal
complexes from Drosophila embryos to study them ex vivo (Gopalakrishnan et al.
2010
; Gopalakrishnan et al.
2011
; Kellogg and Alberts
1992
; Moritz et al.
1995
).
This allows one to study protein interactions under near physiological conditions.
This also opens a window to use purified centrosomal proteins, structures, and
complexes in cell-free experiments that can investigate the individual steps in
centrosome duplication. Ultimately, this can theoretically allow centrosome
duplication and function to be reconstituted using purified components.
Finally: Drosophila centrosomes are formed using conserved proteins and the
overall structure of Drosophila centrosomes is very similar to that of other
organisms, suggesting that the basic mechanisms of centrosome duplication used
in Drosophila are similar to those used in other organisms.
1.2 Centrosomes in Drosophila Development
Centrosomes in Drosophila were studied in some detail in a context of several
developmental processes. In this chapter, we will focus on four processes. The first
two processes take place during early embryonic development: (1) Fertilization,
and (2) Syncytial blastoderm formation. The next two processes occur in differ-
entiated cell types and can be studied during pupal development: (3) Sensory
neuron differentiation, and (4) Spermatogenesis. We will summarize key features
of the centrosome in each of these developmental processes, highlighting unique
properties that have provided insight into the biology of the centrosome.
1.2.1 Fertilization
Fertilization is the process by which the sperm (male gamete) and oocyte (female
gamete) are fused to form a zygote, the first cell of a new organism. In general, a
key step in fertilization is the migration of sperm and oocyte pronuclei toward each
other and their subsequent fusion (Fig.
1.2
).
It is generally recognized that in most animals, including Drosophila, the
oocyte does not contain centrioles (Krioutchkova and Onishchenko
1999
; Man-
andhar et al.
2005
; Sun and Schatten
2007
). Instead, oocytes have acentriolar
centrosomes or microtubule organization centers that participate in female meiosis
and in the formation of the female pronucleus (Megraw and Kaufman
2000
).
While the oocyte does not appear to have centrioles, it does contain a large amount
of centriolar and PCM proteins within its cytoplasm, enough to form 2
13
centro-
somes (Rodrigues-Martins et al.
2007b
). These proteins, contributed by the mother
via
the
oocyte
(maternal
contribution),
are
sufficient
to
support
centrosome
