Cell fate of photoreceptor neurons and subtype specification

Photoreceptor neurons (PRs) in the eye are able to transform distinct wavelengths of the light into neuronal encoded information. The actual translation of “photons into neuronal signals” however is acheived by the rhodopsin genes coding for light-sensitive G-protein coupled receptors. Therefore the expression of a given rhodopsin gene defines to which light a photoreceptor neuron will respond to. In turn the developmental program defining which rhodopsin gene a specific photoreceptor neuron will express is therefor the corner stone of vision.

We therefore investigate and define the molecular and genetic mechanisms controlling terminal differentiation of photoreceptor neurons and rhodopsin expression.

The larval eye of Drosophila represents is a comparably simple visual organ only composed of 12 PRs, which are further subdivided into two types. Four PRs are blue-sensitive defined by the expression of rhodopsin5 (rh5) eight PRs express the green-sensitive rhodopsin6 (rh6).

 We have identified a set of three transcription factors (Sal, Svp and Otd) to be mediating the choice of larval PRs to either express rh5 or rh6 (Sprecher et al., 2007, GENES DEV). The genetic mechanisms are surprisingly different from the ones acting in the retina of the adult animal.

Relevant publications:

Mishra AK, Tsachaki M, Rister J, Ng J, Celik A, Sprecher SG.                                            Binary Cell Fate Decisions and Fate Transformation in the Drosophila Larval Eye.        PLoS Genet. 2013 Dec;9(12):e1004027.

Vasiliauskas D, Mazzoni EO, Sprecher SG, Brodetskiy K, Johnston Jr RJ, Lidder P, Vogt N, Celik A, Desplan C                                                                                                               Feedback from rhodopsin controls rhodopsin exclusion in Drosophila  photoreceptors. NATURE. 2011 Oct 9;479(7371):108-12

Sprecher SG and Desplan C                                                                                                   Switch of rhodopsin expression in terminally differentiated Drosophila sensory neurons. NATURE, 2008 Jul 24 454 (7203):533-537

Sprecher SG, Pichaud F and Desplan C                                                                                  Adult and larval photoreceptors use different mechanisms to specify the same Rhodopsin fates                                                                                                                                            GENES AND DEVELOPMENT 2007 Sep 1;21(17):2182-95.