Biology Reference
In-Depth Information
Fig. 5.2 The centrosome or cell center organizes the cell cytoskeleton and mitotic spindles
composed of MTs. It also establishes the polarity of the cell. Note organelles located between
MTs, which act as guide rails. Courtesy Late Professor P. Motta, Rome
(FM) to label MTs surrounding functional centrosomes (Fig.
5.5
) or with anti-
bodies specific to proteins associated with centrioles and PCM, such as alpha
tubulin or centrin (Schatten
1994
,
2008
; Simerly et al.
1995
; Sutovsky and Sch-
atten
1999
). Centrioles have been traced in all stages of preimplantation
embryogenesis by TEM and even in embryonic stem cells; the sperm centriole is
undoubtedly the precursor of centrioles in all fetal and adult somatic cells (Sa-
thananthan et al.
1996
; Sathananthan
1997
). The maternal centrosome is greatly
reduced in human oocytes, unlike in mouse oocytes that contain dominant
maternal centrosomal material without centrioles. Hence, mice can easily develop
parthenogenetically. Only one dominant, functional centrosome, paternal or
maternal, is required to ensure normal development. The inheritance of two cen-
trioles, as in dispermic fertilization, leads to abnormal development of the ensuing
triploid embryos that may develop to term in humans.
5.3 Methodology
Our studies over three decades are based on the examination of human gameto-
genesis, gametes, and embryos at fertilization and during preimplantation devel-
opment,
where
over
300
normal
bipronuclear
and
abnormal
tripronuclear
