Centromeres are chromosomal loci essential for the correct segregation of genetic material during cell division. Defects in centromere function can lead to aneuploidy and cancer. During early embryonic development in mammals, prior to the first cell division, male and female genomes are separated in pronuclei located at the centre of the zygote. Parental chromatin clusters at the interface between the two pronuclei and this clustering step is critical to avoid aneuploidy in human and bovine zygotes. Yet, despite their essential function in chromosome segregation, the position and spatial organization of centromeres during the first cell cycle in mammals is mostly unknown. Previous studies conducted in bovine embryos derived from in vitro fertilization (IVF) showed that cell cycle progression impacts on the success rate of blastocyst formation. Specifically, embryos that entered earliest into S-phase or the earliest cleaving embryos were more likely to develop into blastocysts. To determine the precise timing of these events we performed a detailed characterization of key phases of the first cell cycle in bovine zygotes derived from IVF. In parallel we examined the spatial positioning of centromeres. We identify 20 h post insemination (hpi) as the timepoint when male and female pronuclei are juxtaposed and are completing S-phase. At this timepoint, we show that centromeres are positioned distal to the pronuclear interface and use super resolution microscopy to demonstrate extensive centromere clustering into chromocentres. Our results identify distinct nuclear features observed at 20 hpi, which may serve as cell cycle markers in determining successful bovine IVF.

The idea of ‘collective memory’ features prominently in several disciplines but rarely in legal scholarship. Drawing on the work of Henri Bergson, Maurice Halbwachs and GWF Hegel, this paper seeks to present an account of collective memory that is relevant to discourse on law and policy. The paper uses the example of the policy response to the European sovereign debt crisis as a means of illustrating how collective memory of events in the distant past can shape individual behaviour and thinking. It argues that the current policy response can be explained, at least in part, by the influence on policy makers of the standard historical narrative of the Great Inflation of Weimar Germany. When, however, collective memory takes the form of Bergsonian ‘habit memory’, it can inhibit our efforts to resolve hard cases and the German government's opposition to the European Central Bank acting as a lender of last resort in the government bond markets neatly illustrates this point. If the debt crisis is to be managed effectively, policy makers must draw on Bergsonian ‘pure memory’ to explore the bounds of political and economic possibility.