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Regulation of human and mouse oocyte maturation in vitro with 6-dimethylaminopurine
C Anderiesz1, C Y Fong, A Bongso
1Centre for Early Human Development, Institute of Reproduction and Development, Monash University, Monash Medical Centre, Clayton, Victoria, Australia.
Abstract:
It has been postulated that premature shortening of the oocyte growth phase due to the recovery of oocytes from small diameter follicles may be responsible for the developmental anomalies associated with in-vitro maturation. 6-Dimethylaminopurine (DMAP) was used to artificially lengthen the pre-maturation period of oocyte growth, in vitro, by inhibiting germinal vesicle breakdown in mouse and human oocytes. DMAP inhibited the meiotic maturation of mouse and human oocytes and the inhibition was fully reversible. The timing of polar body extrusion was accelerated in mouse oocytes following the withdrawal of DMAP; however, the kinetics of nuclear maturation in human oocytes was unaffected by exposure to DMAP. All mouse and human DMAP-treated oocytes that matured to metaphase II expressed histone H1 kinase activity. Fertilization rates in both DMAP-treated and control mouse and human oocytes were comparable, and human embryonic development was similar in control and DMAP-treated oocytes. However, blastocyst development was significantly reduced in DMAP-treated mouse oocytes (P < 0.05). It is concluded that lengthening the prematuration growth phase, by temporarily inhibiting kinase activity with DMAP, does not directly improve oocyte developmental competence but provides a useful tool for further investigating meiotic and developmentally related events in vitro by manipulating meiotic resumption.
Insights
Artificial lengthening of oocyte growth using 6-dimethylaminopurine (DMAP) did not improve developmental competence. This method, however, offers a tool for studying in vitro maturation and meiotic resumption.
Area of Science:
- Reproductive Biology
- Developmental Biology
- Cell Biology
Background:
- Premature oocyte growth phase shortening may cause developmental anomalies in in-vitro maturation.
- Oocyte recovery from small follicles is implicated in these developmental issues.
Purpose of the Study:
- To investigate if artificially lengthening the oocyte pre-maturation growth phase improves developmental competence.
- To utilize 6-dimethylaminopurine (DMAP) to inhibit germinal vesicle breakdown and extend oocyte growth in vitro.
- To explore DMAP's effects on meiotic resumption and oocyte developmental events.
Main Methods:
- Used 6-dimethylaminopurine (DMAP) to inhibit germinal vesicle breakdown in mouse and human oocytes, extending the pre-maturation period.
- Assessed meiotic maturation, polar body extrusion, nuclear maturation kinetics, and histone H1 kinase activity.
- Evaluated fertilization rates and subsequent embryonic development, including blastocyst formation.
Main Results:
- DMAP reversibly inhibited meiotic maturation in both mouse and human oocytes.
- Polar body extrusion was accelerated in mouse oocytes post-DMAP withdrawal; human oocyte nuclear maturation kinetics were unaffected.
- Histone H1 kinase activity was present in DMAP-treated metaphase II oocytes.
- Fertilization rates were comparable between DMAP-treated and control groups.
- Human embryonic development was similar, but mouse blastocyst development was significantly reduced (P < 0.05).
Conclusions:
- Lengthening the oocyte pre-maturation phase via DMAP-induced kinase inhibition does not directly enhance developmental competence.
- DMAP serves as a valuable tool for investigating meiotic events and developmental processes in vitro by manipulating meiotic resumption.