The role of yolk syncytial layer and blastoderm movements during gastrulation in zebrafish
Year: 2007
Type: dissertation
Abstract: During gastrulation, a set of highly coordinated morphogenetic movements creates the\nshape and internal organization of the embryo. In teleostean fishes, these morphogenetic\nmovements involve not only the embryonic progenitor cells (deep cells) but also two\nextra-embryonic tissues: an outer sheet of epithelial cells (EVL) and a yolk syncytial\nlayer (YSL). Epiboly is characterized by the spreading of the blastoderm (deep cells and\nEVL) to cover the large yolk cell, whereas convergence and extension leads,\nrespectively, to mediolateral narrowing and anteroposterior elongation of the embryo.\nRecent studies have shown that the nuclei of the YSL undergo epiboly and\nconvergence and extension movements similarly to the overlying deep cells, suggesting\nthat these tissues interact during gastrulation. However, it is so far not clear whether and\nhow the movements of YSL nuclei and deep cells influence each other.\nIn the first part of this thesis, the convergence and extension movement of YSL\nnuclei was quantitatively compared to the movement of the overlying mesendodermal\nprogenitor (or hypoblast) cells. This revealed that, besides the similarity in the overall\ndirection of movement, YSL nuclei and hypoblast cell movements display differences\nin speed and directionality.\nNext, the interaction between YSL and hypoblast was addressed. The movement\nof the blastoderm was analyzed when YSL nuclei movement was impaired by interfering\nwith the YSL microtubule cytoskeleton. We found that YSL and blastoderm epiboly\nwere strongly reduced, while convergence and extension were only mildly affected,\nsuggesting that YSL microtubules and YSL nuclei movement are required for epiboly,\nbut not essential for convergence and extension of the blastoderm. We also addressed\nwhether blastodermal cells can influence YSL nuclei movement. In maternal-zygotic\none-eyed pinhead (MZoep) mutant embryos, which lack hypoblast cells, YSL nuclei do\nnot undergo proper convergence movement. Moreover, transplantation of wild type\nhypoblast cells into these mutants locally rescued the YSL nuclei convergence\nphenotype, indicating that hypoblast cells can control the movement of YSL nuclei.\nFinally, we propose that the hypoblast influences YSL nuclei movement as a\nresult of shape changes caused by the collective movement of cells, and that this process\nrequires the adhesion molecule E-cadherin.
Author: Lara Cristina de Jesus Carvalho
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W327015155