title: Characterization of green fluorescent protein-expressing retinal cells in CD 44-transgenic mice.
abstract: Sensory information in the retina is transferred from rod and cone photoreceptors to higher visual centers via numerous parallel circuits that sample the photoreceptor mosaic independently. Each circuit consists of a unique combination of ganglion cell, bipolar and amacrine cell types. The morphology and physiological responses of many amacrine cells have been characterized. However, the synaptic connections and retinal circuits in which they participate are only rarely understood. A major problem that has prevented fuller characterization of retinal circuitry is the need for specific cellular markers for the more than 50 inner retinal cell types. One potential strategy for labeling cells is to use transgenic expression of a reporter gene in a specific cell type. In a recent study of cluster of differentiation 44 (CD44)-enhanced green fluorescent protein (EGFP) transgenic mice, we observed that the green fluorescent protein (GFP) was expressed in a population of amacrine and ganglion cells in the inner nuclear layer (INL) and the GCL. To characterize the morphology of the GFP-labeled cells, whole mount preparations of the retina were used for targeted iontophoretic injections of Lucifer Yellow and Neurobiotin. Furthermore, immunocytochemistry was used to characterize the antigenic properties of the cells. We found that many GFP-expressing cells were GABAergic and also expressed calretinin. In addition to the somatic staining, there was a strong GFP(+)-band located about 50-60% depth in the inner plexiform layer (IPL). Double labeling with an antibody to choline acetyltransferase (ChAT) revealed that the GFP-band was located at strata 3 inner retina. The best-labeled GFP-expressing cell type in the INL was a wide-field amacrine cell that ramified in stratum 3. The GFP-expressing cells in the GCL resemble the type B1, or possibly A2 ganglion cells. The CD44-EGFP mice should provide a valuable resource for electrophysiological and connectivity studies of amacrine cells in the mouse retina.
authors.affiliation: Department of Ophthalmology, Northwestern University Feinberg School of Medicine, Northwestern University, Tarry Building, 5-715, 303 East Chicago Avenue, Chicago, IL 60611, USA. vjsarthy@northwestern.edu
authors.forename: V
authors.initials: V
authors.lastname: Sarthy
authors.forename: H
authors.initials: H
authors.lastname: Hoshi
authors.forename: S
authors.initials: S
authors.lastname: Mills
authors.forename: V J
authors.initials: VJ
authors.lastname: Dudley
mesh_terms: D025042:Amacrine Cells / Q000166:cytology / Q000378:metabolism; D000818:Animals; D030801:Animals, Genetically Modified; D015415:Biomarkers; D001710:Biotin / Q000031:analogs & derivatives; D064032:Calbindin 2; D002454:Cell Differentiation / Q000235:genetics; D002795:Choline O-Acetyltransferase / Q000378:metabolism; D005786:Gene Expression Regulation / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics* / Q000378:metabolism; D018960:Hyaluronan Receptors / Q000235:genetics*; D007546:Isoquinolines; D051379:Mice; D009434:Neural Pathways / Q000166:cytology / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D012160:Retina / Q000166:cytology / Q000378:metabolism*; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000378:metabolism; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D015415:Biomarkers; C576511:Calb2 protein, mouse; D064032:Calbindin 2; C476399:Cd44 protein, mouse; D018960:Hyaluronan Receptors; D007546:Isoquinolines; D064030:S100 Calcium Binding Protein G; C485184:enhanced green fluorescent protein; C070614:neurobiotin; D049452:Green Fluorescent Proteins; D005680:gamma-Aminobutyric Acid; D001710:Biotin; C017475:lucifer yellow; D002795:Choline O-Acetyltransferase