30. 07. 2024
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Scientists from the Department of Cell Nucleus Plasticity have published the results of a new study showing the crucial role of proper timing of pronuclear transfer in embryos’ developmental potential. The paper was published in the Molecular Human Reproduction journal (open in a new window) (IF 3.6), Oxford Academic Publishing.
Pronuclear transfer is a technique used in human-assisted reproduction, mainly to prevent mitochondrial diseases and idiopathic developmental arrest. The procedure aims to ensure the birth of a healthy child. Mitochondrial DNA is inherited only from the mother, so if the mother has a mitochondrial disease, so will her children. Pronuclear transfer allows this to be avoided. The pronuclear transfer technique might be viewed as ethically and legally controversial because it involves genetic material from three different individuals (a mother, a father and an egg donor). Nevertheless, it has been used successfully in many cases but is still subject to research and regulation in many countries. Officially, the first country in the world where this method was legalised for clinical practice was the UK in 2016.
The procedure is as follows: the mother’s egg is fertilised with the father’s sperm, creating an embryo with the genetic material of the mother and father contained in the pronuclei. The pronuclei from the mother’s fertilised egg are transferred to the donor egg, which has been activated and stripped of its own genetic material. The resulting embryo, which now contains genetic material from the father and mother (in the nucleus) and healthy mitochondria from the donor, is allowed to develop to the blastocyst stage and then transferred to the mother’s uterus.
Although this method is being used worldwide for therapeutic purposes, a precise protocol has not yet been established, and the consequences of the formation of parental pronucleus in a defective cytoplasm have not yet been systematically studied. Scientists from the Dept. of Cell Nucleus Plasticity have therefore focused on exploring the pronucleus transfer in mouse embryos at different time points after fertilisation. The key factor determining the success proved to be the DNA replication and the conditions under which it takes place. The study shows that the timing of pronuclear transfer should be restricted exclusively to the pre-replication phase.
These findings have the potential to significantly impact the field of assisted reproduction by explaining the reasons behind unsuccessful pronuclear transfer attempts, improving the success rate and quality of embryos, and increasing the safety of procedures used in human-assisted reproduction.