Parthenogenese : [een literatuurstudie over natuurlijke parthenogenese bij gewervelde dieren met aparte bibliografie : een experimentele studie over parthenogenetische stimulatie van muize - eicellen, de vroege in vitro ontwikkeling en pogingen tot bevruchting van deze parthenogenonten]

Dit proefschrift handelt over parthenogenese bij gewervelde dieren. Uit de literatuur blijkt dat het verschijnsel parthenogenese op vele wijzen is gedefinieerd en onderverdeeld in verschillende typen. In hoofdstuk I wordt deze diversiteit beschreven en wordt tevens aangetoond dat, als gevolg van nieuw ontwikkelde laboratorium technieken, het onderscheid parthenogenese versus voortplanting met behulp van bevruchting niet meer toereikend is. Er zijn nu experimentele ontwikkelingspatronen mogelijk die op een combinatie van deze twee voortplantingsmechanismen berusten. Om deze onderscheidingsmoeilijkheden op te lossen wordt een nieuwe terminologie en indeling van mogelijke ontwikkelingspatronen bij gewervelde dieren beschreven.This thesis deals with parthenogenesis in vertebrates. In the literature the phenomenon parthenogenesis is defined in many different ways and classified in different types. This diversion is described in chapter I where it is also shown that - due to newly developped laboratory techniques - the distinction between parthenogenesis and reproduction based on fertilization is not sufficient anymore. Nowadays experimental developmental- patterns have been made possible that are based on a combination of these two mechanisms of reproduction. In order to solve these problerns of distinction a new terminology is proposed and a classification of possible patterns of development of vertebrates is describe

Mechanisms of PLCζ induced Ca²⁺ oscillations in mouse eggs at fertilisation

All the events of egg activation in mammalian eggs are triggered physiologically by transient increases in cytosolic free Ca²⁺ referred to as Ca²⁺ioscillations. These oscillations are initiated by the sperm derived PLC isoform, PLCζ. PLCζ releases Ca²⁺ by hydrolysing its substrate PI(4,5)P₂ to produce IP₃, however, many of the mechanisms by which PLCζ elicits Ca²⁺release in eggs are poorly understood. The results of this thesis confirm that whilstPLCζ cRNA and recombinant protein is able to cause Ca²⁺ioscillations in mouse eggs the sperm derived protein PAWP does not cause any Ca²⁺ release in any circumstances. It is shown that EF hand domain and XY linker of PLCζ are important in determining its Ca²⁺i releasing ability by enabling PLCζ binding to its substrate PI(4,5)P₂ through electrostatic interactions. The C2 domain of PLCζ was also found to play a crucial role in the Ca²⁺ releasing ability of PLCζ, possibly by binding to lipids or proteins in the target membrane. The Ca²⁺releasing ability of eggs is acquired during oocyte maturation and a dramatic increase in PLCζ sensitivity of oocytes occurs after germinal vesicle breakdown.A variety of markers for PLCζ’s substrate PI(4,5)P₂ including fluorescent PI(4,5)P₂ and gelsolin based fluorescent probes suggests that this PI(4,5)P₂ is localised to intracellular vesicles that could derive from Golgi apparatus. Attempts are made to measure PI turnover in these intracellular compartments of eggs during PLCζ induced Ca²⁺i oscillations using several probes. The results of this thesis suggest that PLCζ releases Ca²⁺ by a novel IP₃ based signalling pathway that involves an intracellular source of PI(4,5)P₂