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nucleus have been sparse which may in part be related to the density of the sperm
nucleus that has made experimental and analytical approaches difficult (reviewed
in Johnson et al. 2011 ). The mature sperm nucleus is distinguished from other
nuclei by its extreme chromatin condensation state which is achieved during
spermiogenesis when the majority of histones are replaced by protamines, small
basic proteins that are bound to sperm DNA and become cross-linked through the
formation of disulfide bridges when spermatozoa transit through the epididymis
(reviewed in Delbés et al. 2010 ). Proper chromatin compaction is important for
male factor fertility in which accurate protamine, histone, and nuclear matrix
component functions are essential. Only recently has it been possible to dissect
structural aspects within the sperm nucleus and it has clearly been shown that
nuclear matrix components are present in sperm (reviewed in Johnson et al. 2011 )
which opens up speculations that the nuclear mitotic apparatus (NuMA) protein
may exist within the sperm nucleus. The multifunctional protein NuMA has been
best studied in somatic cells (reviewed in Sun and Schatten 2006 ) and it has been
shown that it plays important roles as nuclear matrix protein in interphase and as
centrosome-associated protein during meiosis and mitosis (reviewed in Sun and
Schatten 2006 ). We do not yet know when NuMA functions become important for
sperm nuclear functions and for nuclear-centrosome relationships but we know for
certain that it plays an important role in the decondensing sperm pronucleus after
fertilization (reviewed in Sun and Schatten 2006 ; Alvarez-Sedo et al. 2011 ; Sch-
atten et al. 2012 ) which will be addressed in Sect. 2 of this chapter. To better
understand yet unexplained causes of male factor infertility it will be important to
determine new methods to better analyze nuclear components in sperm that play a
role in nuclear-centrosome synchrony after fertilization.
4.3 Centrosome-Nuclear Relationships During Pronuclear/
Zygote Stage, Cell Division, and Embryo Development
A schematic representation of the nuclear and centriole-centrosome cycle within
the first embryonic cell cycle is shown in Fig. 4.2 a-d and described in the figure
legend. Significant changes in sperm chromatin structure begin immediately after
fertilization when protamines are replaced by histones and several epigenetic
modifications take place (Chao et al. 2012 ). Sperm chromatin becomes decon-
densed and the sperm nucleus matures into the male pronucleus while the sperm-
derived centriole-centrosome complex matures by recruiting and accumulating
centrosomal components from the sperm-activated oocyte (reviewed in Schatten
and Sun 2010 , 2011a , 2011c ).
Intimate structural and functional relationships between nuclear and centro-
some proteins are important to fulfill cell cycle-specific functions including
microtubule organization, chromosome alignment, and chromosome separation
during the embryo's first cell cycle (reviewed in Schatten 2008 ; Schatten and Sun
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