Gene expression profiling of purified rat retinal ganglion cells.
OBJECTIVE
The phenotype of specialized cells arises, in part, from their characteristic gene expression patterns. Retinal ganglion cells (RGCs) are of wide interest in neuroscience and die in glaucoma and other optic neuropathies. In this study the genes expressed by RGCs were profiled by expressed sequence tag (EST) analysis.


METHODS
ESTs were generated from a cDNA library constructed from RGCs isolated by immunopanning. The RGC genes were compared with published microarray expression profiles from 13 different neural regions. Immunohistochemistry was performed by standard methods.


RESULTS
Clustering of 4791 RGC ESTs identified 2360 unique gene clusters. Of these, 60% represented known genes, 27% uncharacterized genes/ESTs, and 13% novel sequence. Unexpectedly, one of the largest RGC clusters, RESP18, corresponded to a neuroendocrine-specific gene preferentially expressed in the hypothalamus. RESP18 immunoreactivity within the retina was found mainly in the RGC layer. DDAH1, a gene involved in nitric oxide metabolism, was localized to RGC and amacrine layers. Comparison of gene expression patterns across neuronal regions revealed a prominent subset of RGC genes that were overexpressed in dorsal root and trigeminal ganglia. To narrow the search for candidate disease-related genes, RGC genes were mapped to known disease loci for optic neuropathies.


CONCLUSIONS
This work is one of the first efforts to profile gene expression in a purified population of retinal neurons, the RGCs. The profiling, in addition to revealing both known and novel genes underlying the RGC phenotype, also uncovered common patterns of gene expression between RGCs and other sensory ganglia.
Department of Ophthalmology, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
Ronald H
RH
Farkas
Jiang
J
Qian
Jeffrey L
JL
Goldberg
Harry A
HA
Quigley
Donald J
DJ
Zack
D000818:Animals; D020224:Expressed Sequence Tags; D005136:Eye Proteins / Q000235:genetics; D015870:Gene Expression / Q000502:physiology*; D020869:Gene Expression Profiling; D015723:Gene Library; D007124:Immunoenzyme Techniques; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009901:Optic Nerve Diseases / Q000235:genetics; D010641:Phenotype; D051381:Rats; D017207:Rats, Sprague-Dawley; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000378:metabolism*; D016324:Sequence Tagged Sites
D005136:Eye Proteins; D009419:Nerve Tissue Proteins; C086381:regulated endocrine secretory protein 18