Characterization of new transcripts enriched in the mouse retina and identification of candidate retinal disease genes.
OBJECTIVE
Most retinal disease genes are preferentially expressed in photoreceptors, the light-sensitive cells involved in phototransduction. In addition, some of the genes linked to retinal diseases are essential for normal retinal development. The goal of this study was to identify new transcripts enriched in photoreceptors involved in retinal development or diseases.


METHODS
To isolate uncharacterized retinal transcripts, the bioinformatic method Digital Differential Display (DDD) was used. RNA in situ hybridization was used to characterize gene-expression patterns.


RESULTS
Twenty-seven mouse ESTs highly represented in retinal libraries were identified. Eight ESTs were predominantly expressed in photoreceptors and/or in the retinal pigment epithelium (RPE), whereas transcripts for other ESTs were detected more ubiquitously in the retinal cells or abundantly in ganglion cells and/or the inner nuclear layer. Mapping of the corresponding human orthologues of the photoreceptor/RPE-enriched genes revealed that two of them are candidate disease genes for retinitis pigmentosa, loci RP22 and RP28. Both of these are predominantly expressed in rod photoreceptors. The candidate RP22 gene codes for a putative transmembrane protein showing homology to Cln8 (ceroid lipofuscinosis, neuronal 8), in which gene mutations are associated with photoreceptors degeneration in mice. Also identified were two genes expressed in photoreceptors that are candidate disease genes for recessive Bardet-Biedl syndrome type 3 (BBS3) and recessive ataxia with RP (AXPC1).


CONCLUSIONS
This study demonstrates how bioinformatic analysis can be used to identify novel tissue-specific genes relevant to development and diseases.
Maisonneuve-Rosemont Hospital, Montreal, Quebec, Canada.
Julie
J
Lord-Grignon
Nicolas
N
Tétreault
Alan J
AJ
Mears
Anand
A
Swaroop
Gilbert
G
Bernier
D000818:Animals; D050976:Basic-Leucine Zipper Transcription Factors; D019295:Computational Biology / Q000379:methods; D004268:DNA-Binding Proteins / Q000235:genetics; D003626:Data Display; D020224:Expressed Sequence Tags; D005136:Eye Proteins / Q000235:genetics; D017403:In Situ Hybridization; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism; D010857:Pigment Epithelium of Eye / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D012160:Retina / Q000378:metabolism*; D012164:Retinal Diseases / Q000235:genetics*; D017385:Sequence Homology
D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; D005136:Eye Proteins; C490037:NRL protein, human; C084884:Nrl protein, mouse; D012333:RNA, Messenger