to humans and human eye diseases. Control of sleep/wake patterns Melanopsin may aid in controlling sleep cycles and wakefulness. Tsunematsu and colleagues created transgenic mice that expressed melanopsin in hypothalamic orexin neurons. With a short 4-second pulse of blue light (guided by optical fibers), the transgenic mice could successfully transition from slow-wave sleep (SWS), which is commonly known as "deep sleep," to long-lasting wakefulness. After switching off the blue light, the hypothalamic orexin neurons showed activity for several tens of seconds. It has been shown that rods and cones play no role in the onset of sleep by light, distinguishing them from ipRGCs and melanopsin. This provides strong evidence that there is a link between ipRGCs in humans and alertness, particularly with high frequency light (e.g. blue light). Therefore, melanopsin can be used as a therapeutic target for controlling the sleep-wake cycle. Regulation of blood glucose levels In a paper published by Ye and colleagues in 2011, melanopsin was utilized to create an optogenetic synthetic transcription device that was tested in a therapeutic setting to produce Fc-glucagon-like peptide 1 (Fc-GLP-1), a fusion protein that helps control blood glucose levels in mammals with Type II Diabetes. The researchers subcutaneously implanted mice with microencapsulated transgenic HEK 293 cells that were cotransfected with two vectors including the melanopsin gene and the gene of interest under an NFAT (nuclear factor of activated T cells) promoter, respectively. It is through this engineered pathway that they successfully controlled the expression of Fc-GLP-1 in doubly recessive diabetic mice and reduced hyperglycemia, or high blood glucose levels, in these mice. This shows promise for the use of melanopsin as an optogenetic tool for the treatment of Type II diabetes. See also Light effects on circadian rhythm Opsins Intrinsically Photosensitive Retinal Ganglion Cells (ipRGCs) Suprachiasmatic nucleus (SCN) Retinohypothalamic tract References Further reading G protein-coupled receptors Circadian rhythm Human proteins