Abstract
Purpose::
In the absence of Nrl or Nr2e3, rod photoreceptors are transformed to S-cones. Our goal is to test for the existence of photoreceptor precursors that are competent to make binary decisions during early retinogenesis.
Methods::
Using transgenic mice that express Nrl under the control of a Crx (rod and cone precursors) and S-opsin (developing cones) promoter, we examined retinal morphology and immunohistochemistry in a wildtype, Nrl-/-, and rd7 background. Electroretinogram (ERG) studies were carried out to evaluate retinal function, and electromobility shift assays and ChIP were performed to assess the association of Nrl with specific DNA elements.
Results::
Both cone precursors and developing cones transform to functional rod photoreceptors in response to Nrl and Nr2e3 expression. Nrl associates with S-opsin and Thrb promoter elements. In the absence of cone photoreceptors, cone synaptic circuitry is recruited by rods.
Conclusions::
Photoreceptor precursors have the potential to develop into cones or rods and undergo terminal differentiation in response to specific intrinsic information and extrinsic factors.
Keywords: photoreceptors • development • plasticity