Gene mutations impede oocyte maturation, fertilization, and early embryonic development

Infertility is estimated to affect as many as 186 million people worldwide. Although male infertility contributes to more than half of all cases of global childlessness, infertility remains a woman's social burden. Unfortunately, areas of the world with the highest rates of infertility are often those with poor access to assisted reproductive techniques (ARTs). In such settings, women may be abandoned to their childless destinies. However, emerging data suggest that making ART accessible and affordable is an important gender intervention. To that end, this article presents an overview of what we know about global infertility, ART and changing gender relations, posing five key questions: (i) why is infertility an ongoing global reproductive health problem? (ii) What are the gender effects of infertility, and are they changing over time? (iii) What do we know about the globalization of ART to resource-poor settings? (iv) How are new global initiatives attempting to improve access to IVF? (v) Finally, what can be done to overcome infertility, help the infertile and enhance low-cost IVF (LCIVF) activism?

Embryogenesis depends on a highly coordinated cascade of genetically encoded events. In animals, maternal factors contributed by the egg cytoplasm initially control development, whereas the zygotic nuclear genome is quiescent. Subsequently, the genome is activated, embryonic gene products are mobilized, and maternal factors are cleared. This transfer of developmental control is called the maternal-to-zygotic transition (MZT). In this review, we discuss recent advances toward understanding the scope, timing, and mechanisms that underlie zygotic genome activation at the MZT in animals. We describe high-throughput techniques to measure the embryonic transcriptome and explore how regulation of the cell cycle, chromatin, and transcription factors together elicits specific patterns of embryonic gene expression. Finally, we illustrate the interplay between zygotic transcription and maternal clearance and show how these two activities combine to reprogram two terminally differentiated gametes into a totipotent embryo.

Oocytes, the female germ cells, contain all the messenger RNAs necessary to start a new life but typically wait until fertilization to begin development. The transition from oocyte to fertilized egg (zygote) involves many changes, including protein synthesis, protein and RNA degradation, and organelle remodeling. These changes occur concurrently with the meiotic divisions that produce the haploid maternal genome. Accumulating evidence indicates that the cell-cycle regulators that control the meiotic divisions also regulate the many changes that accompany the oocyte-to-zygote transition. We suggest that the meiotic machinery functions as an internal pacemaker that propels oocytes toward embryogenesis.