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Mitosis in the human embryo: the vital role of the sperm centrosome (centriole)
A.H. Sathananthan
Faculty of Health Sciences, La Trobe University, Melbourne, Australia, Institute of Reproduction and Development, Monash Medical Centre, Melbourne, Australia and Department of Obstetrics and Gynaecology, National University Hospital, Singapore
Offprint requests to: Dr. A.H. Sathananthan, Associate Professor/Reader, Faculty of Health Sciences. La Trobe University, Bundoora, Victoria 3083. Australia
Summary. The pattern of sperm centrosomal (centriolar)
inheritance, centrosomal rep lication and perpetuation
during mitosis of the human embryo is reviewed with a
series of electron micrographs . Embryonic cleavage
involves repeated mitoses, a convenient sequence to
study centriolar behaviour during cell division. After the
paternal inheritance of centrioles in the human was
reported (Sathananthan et al.,1991a), there has been an
upsurge of centrosomal research in mammals, which
largely follow the human pattern. The human egg has an
inactive non-functional centrosome.
The paternal centrosome contains a prominent
centriole (proximal) associated with pericentriolar
material which is transmitted to the embryo at
fertilization and persists during sperm incorporation.
Centriolar duplication occurs at the pronuclear stage
(interphase) and the centrosome initially organizes a
sperm aster when male and female pronuclei breakdown
(prometaphase) . The astral centrosome containing
diplosomes (two typical centrioles) splits and relocates
at opposite poles of a bipolar spindle to establish
bipolarization, a prerequisite to normal cell division.
Single or double centrioles occupy pivotal positions on
spindle poles and paternal and matern al chromosomes
organize on the equator of a metaphase spindle, at
syngamy. Bipolarization occurs in all monospermic and
in most dispermicova. Dispermic embryos occasionally
form two sperm asters initially and produce tripolar
spindles ( tripolarization). Anaphase and te lophase
follows producing two or three cells respectively,
completing the first cell cycle.
Descendants of the sperm centriole were found at
every stage of preimplantation embryo development and
were traced from fertilization through cleavage (first
four cell cycles) to the morula and hatching blastocyst
stage. Centrioles were associated with nuclei at
interphase, when they were often replicating and
occupied pivotal positions on spindle poles during
mitosis. Sperm remnants were associated with centrioles
and were fo und at most stages of cleavage. Centrioles
were found in trophoblast, embryoblast and endoderm
cells in hatching blastocysts. Pericentriolar, centrosomal
material nucleated astral and spindle microtubules.
Abnormal nuclear configurations observed in embryos
reflect mitotic aberrations. The bovine embryo closely
resembles the human embryo in centriolar behaviour
during mitosis.
It is concluded that the sperm centrosome is the
functional active centrosome in humans and is likely the
ancestor of centrioles within centrosomes in foetal and
adult somatic cells. The role of the sperm centrosome in
embryogenesis and male infertility is discussed, since it
is of clinical importance in assisted reproduction. Histol Histopathol 12, 827-856
(1997)
Key words: Sperm centriole, Fertilization, Human
embyro, Mitosis, Ultrastructure
DOI: 10.14670/HH-12.827
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