Abstract
The sea urchin embryo provides a valuable system to analyse the molecular mechanisms orchestrating cell cycle progression and mitosis in a developmental context. However, although it is known that the regulation of histone activity by post-translational modification plays an important role during cell division, the dynamics and the impact of these modifications have not been characterised in detail in a developing embryo. Using different immuno-detection techniques, we show that the levels of Histone 3 phosphorylation at Threonine 3 oscillate in synchrony with mitosis in Sphaerechinus granularis early embryos. We present, in addition, the results of a pharmacological study aimed at analysing the role of this key histone post-translational modification during sea urchin early development.
Highlights
Fertilisation is not just the encounter of two gametes; it is a decisive event triggering the transformation of a quiescent egg into an actively developing embryo
Our observations indicate that Haspin could play a major role during the S. granularis first cleavage, but we cannot rule out the possibility that CHR-6494 may inhibit in vivo the activity of other kinases involved in cell cycle progression, like CDK1 [41]
It has been shown that the levels of T3H3 phosphorylated form (T3H3ph) cycle during mitosis in different somatic and germ line cells, the phosphorylation state of T3H3 has not been examined during the early embryogenesis of a metazoan organism
Summary
Fertilisation is not just the encounter of two gametes; it is a decisive event triggering the transformation of a quiescent egg into an actively developing embryo. The dramatic rise in mRNA translation observed in fertilised eggs has been shown to be essential for M-phase completion [4,5], and the contribution of protein phosphorylation to the first mitotic cell cycles has been recognised as crucial [6]. Cell division is the result of a complex series of coordinated events, including chromatin condensation, formation of a bipolar spindle, chromosome alignment and separation of sister chromatids [7]. The regulation of histone activity via post-translational modifications is likely to play a central role during chromatin condensation and chromatid separation [12,13], the dynamics of these modifications and their functional significance have not been studied in depth during sea urchin development [14]. T3H3 phosphorylation is tightly coupled to cell cycle progression and Cyclin B/CDK1 activity during the early embryogenesis of sea urchins
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