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et al.
1991
,
1996
,
2001
; Sathananthan
1991
,
1997
). Such centrioles are present in
poorly motile or immotile sperm, commonly used in ICSI. Since the distal cen-
triole gave rise to the sperm axoneme during spermiogenesis, it is logical to
suppose that the proximal centriole that is inherited by the embryo could cause
aberrant mitosis, as both are derived from the same mother centriole in spermatids.
Our hypothesis was based on defects observed in the proximal centriole in the neck
of sperm from motile, poorly motile, and immotile sperm samples (Sathananthan
1996
; Sathananthan et al.
2001
). Our TEM studies also indicate that the majority
of sperm (80-90 %) from oligoasthenospermic men present centrosomal defects
involving the centriole, PCM, and even the 'black box' surrounding the centro-
somal complex. It is easier to detect centriolar MT defects than to assess aber-
rations of the PCM associated with the centriole. Both components are important
in the overall assessment of the sperm centrosome. Centriolar aberrations may also
be found in a few normal sperm and conversely normal centrioles could be located
in a few poor quality sperm with 0-10 % motility. Of course, defects in the
axoneme of sperm tails have been extensively documented.
The main aberrations of the sperm PC organization are
• disorganization of the MT triplet structure
• loss of MTs within triplets (doublets and singlets)
• loss of MT triplets (half and partial centrioles)
• total loss of the centriole
• displacement of the centriole from its vault within the 'black-box'
• aberrant distribution of PCM—difficult to assess
• disorganization of the 'black box' components
• Intrusion of mitochondria into the neck region
• Intrusion of vesicular elements and dense bodies within the centriole
• double centrioles with single or double axonemes
Some
of
these
aberrations
are
portrayed
in
Fig.
5.26
and
in
our
atlas
(Sathananthan
1996
).
Normal centriolar configuration is essential to ensure duplication and the
functionality of the centrosome to organize embryonic spindles. There is now
increasing clinical evidence to support our hypothesis that poor sperm correlates
with poor embryos (Sathananthan
2009
; Asch et al.
1995
; Vandervorst et al.
1997
;
Chatzimeletiou et al.
2008
; Van Blerkom
1996
; Hinduja et al.
2010
; Hewitson
et al.
1997
; Navara et al.
1995
). A variety of chromosomal aberrations have been
documented in early human embryos, such as aneuploidy, polyploidy, and
mosaicism (Munne
2006
) that could partly be attributed to centrosomal dysfunc-
tion. Centrosomal defects can lead to failure in fertilization, and cause embryonic
arrest through the formation of abnormal spindles and the accumulation of chro-
mosomally abnormal cells that derive from them (Fig.
5.27
). These are some of
the causes of early embryo loss in assisted reproduction causing infertility.
