Localization of the calcium-binding protein secretagogin in cone bipolar cells of the mammalian retina.
Secretagogin, a recently cloned member of the EF-hand family of calcium binding proteins, was localized in the mouse, rat, and rabbit retina using immunofluorescence immunohistochemistry. Secretagogin is expressed in subpopulations of ON and OFF cone bipolar cells; however, no immunoreactivity was observed in rod bipolar cells in any of these species. Using subtype-specific markers and mice expressing green fluorescent protein (GFP) within specific cell classes, we found that secretagogin is expressed in Types 2, 3, 4, 5, 6 and possibly Type 8 cone bipolar cells in the mouse retina. The expression pattern in the rat retina differs slightly with expression in cone bipolar cell Types 2, 5, 6, 7, and 8. Evaluation of secretagogin in the developing mouse retina revealed expression as early as postnatal day 6, with OFF cone bipolar cells showing secretagogin expression prior to the ON cone bipolar cells. Secretagogin is a useful marker of cone bipolar cells for studying alterations in bipolar cell morphology during development and degeneration. Further work will be necessary to elucidate the functional role of this protein in bipolar cells.
Puthussery
Theresa
T
Casey Eye Institute, Department of Ophthalmology, Oregon Health and Sciences University, Portland, Oregon 97239, USA. puthusse@ohsu.edu
Gayet-Primo
Jacqueline
J
Taylor
W Rowland
WR
D000818:Animals; D015415:Biomarkers / Q000032:analysis / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology; D048430:Cell Shape; D005455:Fluorescent Antibody Technique; D049452:Green Fluorescent Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000166:cytology / Q000378:metabolism*; D051245:Retinal Bipolar Cells / Q000166:cytology / Q000378:metabolism*; D017949:Retinal Cone Photoreceptor Cells / Q000166:cytology / Q000378:metabolism*; D064046:Secretagogins
D015415:Biomarkers; D002135:Calcium-Binding Proteins; C576556:SCGN protein, human; D064046:Secretagogins; D049452:Green Fluorescent Proteins