Photoreceptor cells are the sensory cells of the retina, responsible for detecting light and conducting the signals to secondary neurons. Because they cannot be regenerated, loss of photoreceptor cells leads to irreversible blindness. Cell transplantation with postmitotic photoreceptor precursor cells has been shown as a feasible approach to rescue vision in animal models, but the molecular properties of these transplantation-competent cells are not understood. The aims of this thesis are to 1) determine the properties of photoreceptor precursor cells by transcriptome and proteome analysis; 2) identify cell surface molecules that can be used to isolate these cells from cell mixtures and/or that are important for their migration and correct integration in development and in a transplantation context. Nrl/CrxGFP transgene-labelled photoreceptor precursor cells were separated from other retinal cells by flow cytometry and subjected to microarray and mass spectrometry analysis. Bioinformatics analysis showed that the photoreceptor precursor cells were enriched in expression of genes encoding cell projection proteins. Over 200 cell surface molecule candidates were identified and 32 genes encoding confirmed extracellular domains were expressed > 5-fold higher in photoreceptor precursors than other retinal cells. These included the stem cell marker Prom1 (CD133), which was specifically expressed in photoreceptor cells (particularly on their cilia) throughout development as well as on transplanted photoreceptors. Together with CD73 and CD24, it serves as a specific marker to isolate photoreceptor cells for transplantation. An axon guidance molecule Sema7a was shown to be highly expressed in photoreceptor cells. It co-labels with PlxnC1, rather than the expected receptor Itgb1, in developing retina, as well as transplanted migrating photoreceptor cells. Knockout of Sema7a resulted in retinal holes and abnormal photoreceptor synapse projection indicating a role of Sema7a in outer retina lamination. This study sets the foundation for future work on photoreceptor cell surface molecules in development and retinal repair.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:626730 |
| Date | January 2014 |
| Creators | Han, Y. |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://discovery.ucl.ac.uk/1417170/ |
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