Biology Reference
In-Depth Information
4.1 Introduction
Structural and functional relationships between the nucleus and centrosomes are
critically important for successful fertilization, accurate cell division, and proper
embryo development. In somatic interphase cells, centrosomes are closely asso-
ciated with the nuclear surface and structural centrosome-nuclear relationships
have also been shown for C. elegans embryos (Meyerzon et al.
2009
) while studies
to
explore
the
structural
and
functional
centrosome-nuclear
relationships
in
mammalian embryo cells are still only at the beginning.
Is has been well shown in somatic cell systems that precise nuclear-centrosome
synchrony is essential for mitosis and cytokinesis when centrosomes, microtu-
bules, and chromosomes need to interact precisely to fulfill mitotic checkpoint
licensing and coordinate chromosome separation for accurate cell division
developing embryo, centrosomes and the nucleus have to coordinate both sym-
metric and asymmetric cell divisions to distribute cellular components and cell fate
determinants to the dividing daughter cells which is important for cell differenti-
ation. As our previous reviews have addressed the role of centrosomes in oocyte
maturation (Schatten and Sun
2011b
), fertilization (Schatten and Sun
2009a
,
2009b
,
2010
,
2011a
,
2011c
), and male factor infertility (Schatten et al.
2011
)we
will focus the present review on 1) The sperm centriole-centrosome complex and
associations with the sperm nucleus before fertilization; 2) Centrosome-nuclear-
synchrony during pronuclear/zygote stage, cell division, and embryo development;
and 3) Centrosome-nuclear interactions and reprogramming abnormalities in
somatic cell nuclear transfer (SCNT) embryos.
4.2 The Sperm Centriole-Centrosome Complex
and Associations with the Sperm Nucleus
Before Fertilization
In non-rodent mammalian systems, the sperm contains one proximal and one distal
centriole that are organized perpendicular to each other (Fig.
4.1
) and located
within the sperm's connecting piece between the midpiece and the sperm's
nucleus. Only the proximal centriole is associated with the sperm nucleus and
surrounded by a small amount of centrosomal proteins including c-tubulin and
centriole-associated centrin as well as other newly discovered centrosomal com-
ponents (Goto et al.
2010
) for which functions remain to be determined (reviewed
in Schatten and Sun
2011a
,
2011b
,
2011c
). The distal centriole is associated with
the sperm tail and its functions primarily include organization and assembly of
sperm tail microtubules. The close association and functional relationships of the
proximal centriole with the sperm nucleus has been assessed on structural levels
before fertilization and it becomes clearly apparent after fertilization when the
