Can Nucleoli Be Markers of Developmental Potential in Human Zygotes?

In 1999, Tesarik and Greco reported that they could predict the developmental potential of human zygotes from a single static evaluation of their pronuclei. This was based on the distribution and number of specific nuclear organelles – the nucleoli. Recent studies in mice show that nucleoli play a key role in parental genome restructuring after fertilization, and that interfering with this process may lead to developmental failure. These studies thus support the Tesarik–Greco evaluation as a potentially useful method for selecting high-quality embryos in human assisted reproductive technologies. In this opinion article we discuss recent evidence linking nucleoli to parental genome reprogramming, and ask whether nucleoli can mirror or be used as representative markers of embryonic parameters such as chromosome content or DNA fragmentation.

TrendsZygotic nucleoli are of maternal origin: they are not formed de novo. Instead, they are strictly inherited from oocytes.Maternal (oocyte) nucleoli are crucial for normal development but are necessary only shortly after fertilization. When embryos pass the critical period, they are capable of developing to term.Oocyte nucleoli do not represent the building blocks for fully differentiated embryonic nucleoli.Oocyte nucleoli do not participate in embryonic ribosome production reinitiation.Nucleoli in zygotes serve as the site of epigenetic remodeling of parental centromeres: this process occurs on their surface.