Abstract
Purpose: :
In the developing embryo, primitive ectoderm is lineage-restricted in response to extrinsic factors, first forming ectoderm, then neuroectoderm, which among other tissues, forms the retina. The neural inducer Noggin plays a key role in inducing retinal cell markers in cultured human embryonic stem (ES) cells. In direct contrast, mouse ES cells do not express retinal markers in response to Noggin. It has recently been found that human ES cells share more characteristics (morphology, activin/Nodal responsiveness and restricted pluripotency) with mouse primitive ectoderm than with mouse ES cells. We conducted our study to determine if driving mouse ES cells to a primitive ectoderm lineage would allow them to respond to Noggin, and induce retinal cell markers.
Methods: :
Mouse embryonic stem cells treated with conditioned media have the morphology, gene expression profile, differentiation potential and characteristic cytokine responsiveness of primitive ectoderm. Primitive ectoderm was generated from mouse ES cells then treated with Noggin and other extrinsic factors. Quantitative real time PCR was used to measure the relative levels of markers normally expressed in ES cells, primitive ectoderm, ectoderm, neuroectoderm and retinal cells.
Results: :
When treated with Noggin, cultured cells exhibited a morphology similar to cone photoreceptors. Real time PCR confirmed the expression of cone photoreceptor-specific markers in treated cells, including s-opsin and crx.
Conclusions: :
These results suggest that first restricting mouse ES cells to a primitive ectoderm lineage is required for Noggin to induce retinal cell marker expression.
Keywords: retinal development • photoreceptors • cytokines/chemokines