Allan F. Wiechmann


Associate Professor, Department of Cell Biology


B.S., Biological Sciences, University of California, Davis, California
Ph.D., Anatomy, University of California, Los Angeles, California


Distribution of melatonin receptors in the retina:

The goal of our research is to advance our understanding of how circadian signals influence the health of ocular tissues, and to apply this knowledge to the treatment of human ocular disease. We have identified receptors for the circadian signaling molecule, melatonin in the retina and other ocular tissues, notably the sclera, ciliary epithelium, choroid, and corneal epithelium. We are seeking to identify the specific subpopulations of cells in the retina that respond to nocturnal melatonin to alter the sensitivity of the retina to environmental light and to optimize circadian cellular activities. This knowledge will give us a better understanding about how circadian rhythms affect retinal dark adaptation, sensitivity to light, and tissue homeostasis.

Circadian influences on corneal epithelium homeostasis and disease:

The surface of the corneal epithelium is a unique stratified epithelium that provides a crucial barrier to ocular infection, and has a major role in the maintenance of corneal transparency and homeostasis. The daily balance of corneal surface epithelium maturation and desquamation is a critical factor in maintaining the integrity of the barrier function. The intercellular junctions that comprise the barrier in the surface layer of cells must be actively disrupted on a daily basis to enable the surface cells to be shed as part of a renewal process, and the underlying layer of cells must then quickly form new intercellular junctions to maintain the integrity of the protective barrier. We propose that circadian signals, mediated via activation of melatonin receptors on the corneal epithelium, orchestrate the temporal sequence of activities required for the daily shedding and maturation of the surface cells. We are employing a variety of molecular and cellular approaches to investigate the mechanisms by which junctional barriers are degraded and re-established on a daily basis. These studies may help to develop new therapeutic strategies to enhance barrier function of corneas recovering from injury or disease.



AF, Ceresa BP, and Howard EW. (2014) Diurnal variation of tight junction integrity associates inversely with matrix metalloproteinase expression in Xenopus laevis corneal epithelium: Implications for circadian regulation of homeostatic surface cell desquamation. PLoS One; 9(11):e113810.

Wiechmann AF and Sherry DM (2012) Melatonin receptors are anatomically organized to modulate transmission specifically to cone pathways in the retina of Xenopus laevis. J Comp Neurol 520:1115-1127.

Wiechmann AF, Hollaway LR and Summers Rada JA (2009) Melatonin receptor expression in Xenopus laevis surface corneal epithelium: Diurnal rhythm of lateral membrane localization. Mol Vision 15:2384-2403.

Summers Rada JA and Wiechmann AF (2006) Melatonin receptors in chick ocular tissues: Implications for a role of melatonin in ocular growth regulation. Invest Opthalmol Vis Sci 37:25-33.

Wiechmann AF, Udin SB and Summers Rada JA (2004) Localization of Mel1b melatonin receptor-like immunoreactivity in ocular tissues of Xenopus laevis. Exp Eye Res 79:585-594.

Wiechmann AF, Vrieze, MJ, Dighe RK and Hu Y (2003) Direct modulation of rod photoreceptor responsiveness through a Mel1c melatonin receptor in transgenic Xenopus laevis retina. Invest Opthalmol Vis Sci 44:4522-4531.

Wiechmann AF and Rada JA (2003) Melatonin receptors are expressed in the cornea and sclera of the Xenopus laevis eye. Exp Eye Res 77:227-237.

Wiechmann AF and Wirsig-Wiechmann CR (2001) Melatonin receptor RNA and protein expression in Xenopus laevis nonpigmented ciliary epithelial cells. Exp Eye Res 73: 617-623.

Wiechmann AF and Smith AR (2001) Melatonin receptor RNA is expressed in photoreceptors and displays a cyclic rhythm in Xenopus retina. Mol Brain Res, 91: 104-111.

Wiechmann AF, Campbell LD and DM Defoe (1999) Melatonin receptor RNA expression in Xenopus retina. Mol Brain Res, 63: 297-303.

Wiechmann AF and MK Sinacola (1997) Diurnal expression of recoverin in the retina. Mol Brain Res, 45: 321-324.

Wiechmann AF and WK O'Steen (1992) Melatonin increases photoreceptor susceptibility to light-induced damage. Invest Opthalmol Vis Sci, 33: 1894-1902.

Complete List of Published work in MyBibliography:


University of Oklahoma Health Sciences Center
Department of Cell Biology
940 Stanton L. Young Blvd.
Oklahoma City, OK 73104
Phone: (405) 271-8001 ext. 45522
Fax: (405) 271-3548