May 2008
Volume 49, Issue 13
ARVO Annual Meeting Abstract  |   May 2008
Defects in Patterning and Maintenance of Retinal Domains in AP-2 Knockout Mice
Author Affiliations & Notes
  • E. A. Bassett
    Pathology/Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
  • M. Ershadi
    Pathology/Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
  • T. Williams
    Departments of CFB and CDB, University of Colorado, Denver, Colorado
  • J. A. West-Mays
    Pathology/Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
  • Footnotes
    Commercial Relationships  E.A. Bassett, None; M. Ershadi, None; T. Williams, None; J.A. West-Mays, None.
  • Footnotes
    Support  NIH EY11910 (JWM); NIH DE-12728 (TW)
Investigative Ophthalmology & Visual Science May 2008, Vol.49, 3735. doi:
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    • Get Citation

      E. A. Bassett, M. Ershadi, T. Williams, J. A. West-Mays; Defects in Patterning and Maintenance of Retinal Domains in AP-2 Knockout Mice. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3735.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose: : Our previous studies have demonstrated a requirement for transcription factor AP-2α in the development of multiple ocular tissues, including the lens, cornea and optic cup. We have shown that, although AP-2α is not expressed in the retinal pigmented epithelium (RPE), AP-2α germ-line knockout (KO) mice exhibit replacement of the RPE by neural tissue that appears to be a duplicated, inverted neural retina (NR). Conditional deletion of AP-2α from the developing NR does not cause retinal defects, suggesting that the optic vesicle/cup in AP-2α KOs fails to receive the correct RPE-specifying signals from non-retinal tissues. To further assess the nature and timing of alterations in the optic vesicle/cup that lead to the replacement of RPE by a duplicated NR, we have examined AP-2α KOs in detail at multiple stages of optic cup development.

Methods: : Mice heterozygous for the AP-2α gene were used to generate AP-2α KOs at a spectrum of embryonic stages, starting at E9.5. The developing optic cups were examined using histological and immunofluorescent techniques.

Results: : At E9.5, optic vesicles (OVs) evaginated from the forebrain of AP-2α KOs, but were mispositioned. In contrast to their wildtype littermates, the anterior portion of the OV (future NR) in AP-2α KOs failed to orient itself correctly with respect to the surface ectoderm and instead predominantly faced the periocular mesenchyme. At this stage, expression of the NR-specific transcription factor Chx10 was delayed in AP-2α KOs, and the RPE determination gene Otx2 was expressed throughout the OV rather than segregating to the dorsal region (presumptive RPE). While the majority of AP-2α KOs were able to form a bilayered optic cup with a NR that showed normal progression of lamination at earlier stages, a portion of the outer layer commonly lost expression of the RPE markers Mitf and Otx2. This region expressed NR markers and did not become thinner and form a pigmented monolayer.

Conclusions: : Our studies of AP-2α KO mice show that loss of AP-2α in non-retinal tissues has an early impact on specification of retinal domains, beginning at the OV stage. These non-cell autonomous effects of AP-2α influence both the position of the optic vesicle/cup, and the expression of genes required to specify and maintain the RPE and NR territories. AP-2α KOs continue to provide a useful model for studying the tissue-tissue interactions and signals required for the regionalization of retinal domains.

Keywords: retinal development • transgenics/knock-outs • transcription factors 

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