Biology Reference
In-Depth Information
oocyte were able to remodel the donor cell's NuMA although it took 6 h for the
remodeling to take place.
While we do not yet know the exact molecular composition of the zygotic
centrosome and we also do not yet know how it compares to the interphase
somatic cell centrosome and to the centrosome in reconstructed eggs we know that
precise regulation is important for centrosome functions. Phosphorylation plays a
significant role in centrosome functions and we know from cancer cell centro-
somes that abnormal increases in phosphorylation results in increased microtubule
nucleation with consequences for abnormal spindle formation (Lingle et al.
1998
).
In somatic cells, NuMA is in part regulated by cyclin B (reviewed in Sun and
Schatten
2006
) but the regulation of NuMA is still unknown for mammalian
embryonic cells. It is possible that the NuMA-related abnormalities that we found
in human oocytes (Alvarez-Sedó et al.
2011
; Schatten et al.
2012
) may have been
the result of inaccurate regulation by the fertilized ooplasm. It is also possible that
NuMA may be part of the sperm's nuclear matrix that may play a role in nuclear
matrix instability and dysfunctions (reviewed by Johnson et al.
2011
).
Taken together, while we have started to analyze nuclear-centrosome rela-
tionships and centrosome-nuclear reprogramming more detailed studies are needed
to determine how the somatic cell centrosome becomes remodeled to fulfill the
functions of the embryo's blended centrosome that contains precise amounts and
compositions of centrosomal proteins that are precisely regulated by the fertilized
oocyte to serve embryo-specific functions including symmetric and asymmetric
cell divisions during embryo differentiation and development.
4.5 Conclusion and Future Perspectives
Numerous lines of evidence have established the importance of centrosome-
nuclear interactions and synchronized cell cycle progression to ensure accurate
fertilization, zygote formation, and cell divisions during embryogenesis. However,
most of our knowledge of centrosome-nuclear regulation comes from somatic
cells and more research is needed to study abnormalities underlying male and
female factor infertility problems and developmental abnormalities related to
dysfunctions in centrosome-nuclear interactions.
References
Alvarez Sedó CA, Schatten H, Combelles C, Rawe VY (2011) The nuclear mitotic apparatus
protein NuMA: localization and dynamics in human oocytes, fertilization and early embryos.
Mol Hum Reprod 17(6):392-398
Askjaer P et al (2002) Ran GTPase cycle and importins alpha and beta are essential for spindle
formation and nuclear envelope assembly in living Caenorhabditis elegans embryos. Mol Biol
Cell 13:4355-4370
