Open Access Highly Accessed Open Badges Research article

Development of melanopsin-based irradiance detecting circuitry

David S McNeill1, Catherine J Sheely1, Jennifer L Ecker1, Tudor C Badea,3, Duncan Morhardt2, William Guido2* and Samer Hattar1*

Author Affiliations

1 Department of Biology, Johns Hopkins University, Baltimore, MD 21218, USA

2 Department of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond, VA 23298, USA

3 Retinal Circuit Development and Genetics Unit, N-NRL/NEI/NIH, Bethesda, MD 20892-0610, USA

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Neural Development 2011, 6:8  doi:10.1186/1749-8104-6-8

Published: 18 March 2011



Most retinal ganglion cells (RGCs) convey contrast and motion information to visual brain centers. Approximately 2% of RGCs are intrinsically photosensitive (ipRGCs), express melanopsin and are necessary for light to modulate specific physiological processes in mice. The ipRGCs directly target the suprachiasmatic nucleus (SCN) to photoentrain circadian rhythms, and the olivary pretectal nucleus (OPN) to mediate the pupillary light response. How and when this ipRGC circuitry develops is unknown.


Here, we show that some ipRGCs follow a delayed developmental time course relative to other image-forming RGCs. Specifically, ipRGC neurogenesis extends beyond that of other RGCs, and ipRGCs begin innervating the SCN at postnatal ages, unlike most RGCs, which innervate their image-forming targets embryonically. Moreover, the appearance of ipRGC axons in the OPN coincides precisely with the onset of the pupillary light response.


Some ipRGCs differ not only functionally but also developmentally from RGCs that mediate pattern-forming vision.