How does an egg cell reprogram an adult cell nucleus during somatic cell nuclear transfer?

In somatic cell nuclear transfer (SCNT), the egg cell acts as a biological environment that facilitates the reprogramming of a differentiated adult cell nucleus. Once the somatic nucleus is transferred into an enucleated egg—an egg cell from which its own nucleus has been removed—it is exposed to cytoplasmic factors present within the egg.12

These egg cytoplasmic factors interact with the donor nucleus, effectively "resetting" its genetic expression. Through this process, the specialized adult nucleus is reprogrammed to function like the nucleus of a zygote, or fertilized egg, allowing it to guide embryonic development. While the specific molecular mechanisms by which this reprogramming occurs were not fully understood at the time of Ian Wilmut's pioneering work with Dolly, his successful use of this technique demonstrated that egg cells possess the inherent ability to undifferentiate previously specialized nuclei. This discovery remains a fundamental aspect of modern stem cell research and our understanding of cellular development.12