Biology Reference
In-Depth Information
Fig. 5.17 Mouse centrosomes. The sperm has no centrosome (centriole) in its neck, since the
maternal centrosome is dominant (right). Note functional centrosome composed of fine
granulovesicular material in the mouse oocyte, nucleating MTs. Note differences in sperm
structure compared to that of humans x7,000, x50,000
Fig. 5.18 Mouse centrosomes. The sperm has no centrosome (centriole) in its neck, since the
maternal centrosome is dominant (right). Note functional centrosome composed of fine
granulovesicular material in the mouse oocyte, nucleating MTs. Note differences in sperm
structure compared to that of humans x7,000, x50,000
the ooplasm at the bipronuclear stage of fertilization (Sathananthan et al.
1996
;
Sathananthan
1996
,
1997
). Further, the sperm centriole is already associated with
some PCM and this could act as a template to attract maternal centrosomal
material (such as gamma-tubulin). Thus both paternal and maternal centrosomes
are actively engaged to produce a composite zygote centrosome. This activation
could be mediated by sperm cytosolic factors and the Ca
++
transient that occurs
soon after sperm-egg fusion at the onset of fertilization (Schatten
1994
; Simerly
et al.
1995
; Sutovsky and Schatten
1999
). A Ca
++
activated protein, associated
with the sperm centrosome, might be also involved in its release and activation.
