11 DNA Replication during Animal Development and Its Relevance to Gene Expression

Abstract

Animal development has to coordinate cell proliferation and differentiation in order to produce, from a single egg cell, an organism containing billions of cells and tens of different cell types. For this to happen, the DNA replication program must be adapted to different cell fates and to specific transcriptional programs. Intrinsic properties of replication can be modulated, such as fork speed, temporal order of replication, and origin usage, and the changes can be linked to developmental programs in diverse ways. The changes in replication timing that occur during different stages of development or in conjunction with differentiation have been deeply investigated and are reviewed in Chapter 10. Here, we review the changes in DNA replication that occur during animal development, with a special focus on the regulation of origin usage in relation to development and transcription. Indeed, the replicon hypothesis was proposed in 1962 as a way to explain how DNA replication might be linked to cell growth (Jacob et al. 1964). In multicellular organisms, DNA replication must be linked not only to cell growth but also to cell differentiation. Accordingly, the evolution of metazoans might have involved a transition from the strict use of sequence-specific replication origins to a recognition of DNA replication origin more adapted to the adoption of different cell fates in the different tissues of an organism (Méchali 2001).

FIRST ROUND OF REPLICATION
The first replication event during animal development occurs a few hours after fertilization, as a prerequisite for the first division. This event has...