Author's School

Graduate School of Arts & Sciences

Author's Department/Program

Biology and Biomedical Sciences: Developmental, Regenerative and Stem Cell Biology


English (en)

Date of Award

January 2010

Degree Type


Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

David Beebe


THE ROLE OF PAX6 IN LENS PLACODE FORMATION by Jie Huang Washington University in St. Louis, 2010 Professor David Beeebe, Chairperson Although placodes are ubiquitous precursors of tissue invagination, the mechanism of placode formation and its importance for invagination are unclear. We tested the "restricted expansion hypothesis" of lens placode formation by conditionally deleting the transcription factor, Pax6, or the matrix component, Fn1. Deletion of Pax6 from the lens-forming ectoderm prevented placode formation without altering cell proliferation or volume. Pax6CKO ectoderm expanded, rather than being constrained to a constant area, as normally occurs during lens placode formation, and expressed lower levels of transcripts encoding several extracellular matrix components. Deletion of Fn1, which is required to organize the extracellular matrix, prevented lens placode formation. Consistent with the "restricted expansion hypothesis," Fn1CKO ectoderm expanded, rather than being constrained. Ectoderm cells of Fn1CKO embryos expressed markers of lens induction, reorganized their cytoskeleton as in wild type ectoderm, but did not invaginate. These results suggest that placode formation establishes the minimal mechanical requirements for tissue invagination.


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