Preventing aneuploidy: The groom must wait until the bride is ready

Fertilization often triggers the final step of haploidization of the female gamete genome. In this issue, Mori et al. (2021. J. Cell Biol.https://doi.org/10.1083/jcb.202012001) identify two successive actin-dependent mechanisms that delay fusion of maternal and paternal chromosomes, preventing inadvertent elimination of paternal chromosomes together with maternal ones.

Unscrambling the oocyte and the egg: clarifying terminology of the female gamete in mammals

Most reproductive biologists who study female gametes will agree with the 16th century anatomist William Harvey’s doctrine: ‘Ex Ovo Omnia’. This phrase, which literally translates to ‘everything from the egg’, recognizes the centrality of the egg in animal development. Eggs are most impressive cells, capable of supporting development of an entirely new organism following fertilization or parthenogenetic activation. Not so uniformly embraced in the field of reproductive biology is the nomenclature used to refer to the female germ cell. What is an oocyte? What is an egg? Are these terms the same, different, interchangeable? Here we provide functional definitions of the oocyte and egg, and how they can be used in the context of mammalian gamete biology and beyond.

Understandings of Detriment for Resolving Frozen Embryo Disputes

Continuing my previous reference to Alise Panitch's argument that estoppel would be a useful tool for resolving frozen embryo disputes, this article develops her research with reference to the condition of detriment in estoppel. Though Panitch refers to the 'time, money, and psychological commitment necessarily expended in pursuing the full commitment (of IVF)', these notions with respect to detriment have been significantly overlooked, especially in the courts and to a lesser degree in academic literature. This article will accordingly contemplate the physical, psychological and financial detriments to gamete providers if embryos are used against their wishes. Detriment can operate in a variety of circumstances and this article details how detriment could affect women who have sustained repeated failed IVF cycles, and how age affects the subject as well. Following this discussion, it is considered how detriment may affect men and gamete providers not seeking implantation. This leads to a conclusion that detriment is a more significant factor for the female gamete provider seeking implantation.

High potassium seawater inhibits ascidian sperm chemotaxis, but does not affect the male gamete chemotaxis of a brown alga

SummaryMale gamete chemotaxis towards the female gamete is a general strategy to facilitate the sexual reproduction in many marine eukaryotes. Biochemical studies of chemoattractants for male gametes of brown algae have advanced in the 1970s and 1980s, but the molecular mechanism of male gamete responses to the attractants remains elusive. In sea urchin, a K+ channel called the tetraKCNG channel plays a fundamental role in sperm chemotaxis and inhibition of K+ efflux through this channel by high K+ seawater blocks almost all cell responses to the chemoattractant. This signalling mechanism could be conserved in marine invertebrates as tetraKCNG channels are conserved in the marine invertebrates that exhibit sperm chemotaxis. We confirmed that high K+ seawater also inhibited sperm chemotaxis in ascidian, Ciona intestinalis (robusta), in this study. Conversely, the male gamete chemotaxis towards the female gamete of a brown alga, Mutimo cylindricus, was preserved even in high K+ seawater. This result indicates that none of the K+ channels is essential for male gamete chemotaxis in the brown alga, suggesting that the signalling mechanism for chemotaxis in this brown alga is quite different from that of marine invertebrates. Correlated to this result, we revealed that the channels previously proposed as homologues of tetraKCNG in brown algae have a distinct domain composition from that of the tetraKCNG. Namely, one of them possesses two repeats of the six transmembrane segments (diKCNG) instead of four. The structural analysis suggests that diKCNG is a cyclic nucleotide-modulated and/or voltage-gated K+ channel.

Mouse oocyte development - Methods and Protocols

The Springer Protocols series “Methods in Molecular Biology” has published its 1818th volume which is entirely devoted to the development of the female gamete: the oocyte.