Investigation of patterning in early mouse development

• Main Author: Labrousse, Claire A.
• Published: University of Oxford 2007
• Subjects: 571.861
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487279

Re-patterning is visible and well understood in some species. However, controversy remains as to whether there is pre-patterning in the mouse and if so when and how it is established. In this thesis I looked in detail at the first c1~avage division. FirstIy, the role of the sperm was studied. Marking the position of the anterior end of ft~e sperm tail with oil drops in the zona pellllcida provided evidence against a relation i~tween the sperm and the first cleavage. Embedding the zygotes in alginate with a .fertilisation cone present concurred with the oil marking result in rejecting a role for :~perm in defining the plane offirst cleavage. ' ' :;§econdly, time-lapse recording of the first cell cycle allowed observation of movement :pfpronuclei, polar body and zygote inside its zona pellllcida. Pronuclei were found to fOllow two patterns of migration: they either migrated individually directly to the ;§p.tre of the zygote, or, the male joined the female and both migrated together to the #ntre. A potential effect of attraction of forming pronuclei was discovered which need ~o.:be further investigated. The polar body was found to be frequently associated with IecIeavage plane; it was also observed that nearly all the polar bodies presented some ;a,iformation, elongation of the full body or just some localised extension. The zygote t'as found not to rotate extensively within its zona pellllcida, and the few cases where fertilisation cone was observed agreed with previous results where sperm was not associated with cleavage plane. -Filially the role of cell contact at cleavage stages was investigated. Cell contact was Thu.nd not to influence the formation of blastocyst as might be expected, but still to interfere with normal development as many more abnormalities were found in cases Where cell contacts were removed earlier on.