Biology Reference
In-Depth Information
essential to appreciate the diversity of reproductive mechanisms and to speed the
discovery of therapies that allow the more efficient treatment of infertility,
including in humans. We, and others, have found a striking number of morpho-
logical and physiological phenomena in the domestic cat that are relevant to
addressing fertility issues in both men and women. Among the commonalities
between the cat and human are the temporal profiles of folliculogenesis and oocyte
maturation (Pelican et al.
2006
; Comizzoli et al.
2011
) as well as the expression of
teratospermia, a condition whereby [60 % of ejaculated spermatozoa are pleio-
morphic (Pukazhenthi et al.
2006
).
More recently, we have both characterized and examined the significance of cat
sperm centrosome--the paternally inherited organelle essential to successful fer-
tilization (via sperm aster formation) and early embryo development (Schatten and
Sun
2011
). The first centrosomal study in the cat occurred almost 30 years ago
with transmission electron microscopy confirming the presence of a pair of sperm
centrioles in the neck region with the more distal centriole clearly undergoing
various degrees of degeneration compared to the intact, proximal counterpart
(Sato and Oura
1984
; Schmehl and Graham
1989
). This ultrastructure was similar
to other observations made in non-rodent mammals, including the sheep, bull,
rhesus monkey, and human (for review see Manandhar et al.
2005
). Interestingly,
there have been few studies about centrosomal function in felids or in carnivores in
general. In our recent studies (Comizzoli et al.
2006
), we first confirmed that the
cat sperm centrosome played a critical role in fertilization and early embryo
development. Specifically, we determined that proper sperm aster formation is
mainly directed by the paternal centrosome and is crucial for pronuclear migration
and apposition as well as first mitotic spindle formation, as has been shown in
other species (Schatten and Sun
2011
). We also discovered that a larger size cat
sperm aster correlates well with early embryo developmental success to the
blastocyst stage (Comizzoli et al.
2006
), as has been observed in bovine (Navara
et al.
1996
) and human (Terada et al.
2002
,
2010
) systems.
Besides increasing our fundamental base of knowledge, the characterizations of
normal centrosomal structure and function in the cat can have applied relevance to
addressing certain fertility issues. These conditions are significant in that sperm
centrosomal dysfunctions have been identified to contribute to infertility in men
(Van Blerkom and Davis
1995
). There have been a few investigations of centro-
somal functions involving heterologous human sperm injections into bovine or
rabbit oocytes (Terada et al.
2002
). However, the etiology of centrosomal
dysfunctions remains poorly understood, and means for mitigation are still lacking
(Schatten and Sun
2011
; Terada et al.
2010
).
The objective of this review is to highlight the value and detailed findings of
sperm centrosomal studies, specifically in the domestic cat model. Such studies are
providing new insights into the role of this organelle, a better understanding of its
dysfunction, and potential means for overcoming such biological anomalies that
may have relevance to improving human reproductive health.
