Altered expression of genes of the Bmp/Smad and Wnt/calcium signaling pathways in the cone-only Nrl-/- mouse retina, revealed by gene profiling using custom cDNA microarrays.
Many mammalian retinas are rod-dominant, and hence our knowledge of cone photoreceptor biology is relatively limited. To gain insights into the molecular differences between rods and cones, we compared the gene expression profile of the rod-dominated retina of wild type mouse with that of the cone-only retina of Nrl(-/-) (Neural retina leucine zipper knockout) mouse. Our analysis, using custom microarrays of eye-expressed genes, provided equivalent data using either direct or reference-based experimental designs, confirmed differential expression of rod- and cone-specific genes in the Nrl(-/-) retina and identified novel genes that could serve as candidates for retinopathies or for functional studies. In addition, we detected altered expression of several genes that encode cell signaling or structural proteins. Prompted by these findings, additional real-time PCR analysis revealed that genes belonging to the Bmp/Smad and Wnt/Ca(2+) signaling pathways are expressed in the mature wild type retina and that their expression is significantly altered in the Nrl(-/-) retina. Chromatin immunoprecipitation analysis of adult retina identified Bmp4 and Smad4, which are down-regulated in the Nrl(-/-) retina, as possible direct transcriptional targets of Nrl. Consistent with these studies, Bmp4 and Smad4 are expressed in the mature rod photoreceptors of mouse retina. Modulation of Bmp4 and/or Smad4 by Nrl may provide a mechanism for integrating diverse cell signaling networks in rods. We hypothesize that Bmp/Smad and Wnt/Ca(2+) pathways participate in cell-cell communication in the mature retina, and expression changes observed in the Nrl(-/-) retina reflect their biased utilization in rod versus cone homeostasis.
Yu
Jindan
J
Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan 48015, USA.
He
Shirley
S
Friedman
James S
JS
Akimoto
Masayuki
M
Ghosh
Debashis
D
Mears
Alan J
AJ
Hicks
David
D
Swaroop
Anand
A
D000818:Animals; D050976:Basic-Leucine Zipper Transcription Factors; D052004:Bone Morphogenetic Protein Receptors; D020013:Calcium Signaling; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000378:metabolism; D005136:Eye Proteins; D020869:Gene Expression Profiling / Q000379:methods; D005786:Gene Expression Regulation; D051379:Mice; D018345:Mice, Knockout; D020411:Oligonucleotide Array Sequence Analysis; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D017978:Receptors, Growth Factor / Q000378:metabolism; D017949:Retinal Cone Photoreceptor Cells / Q000378:metabolism*; D012164:Retinal Diseases / Q000235:genetics; D017948:Retinal Rod Photoreceptor Cells / Q000378:metabolism*; D051785:Smad Proteins; D015534:Trans-Activators / Q000378:metabolism; D051153:Wnt Proteins
D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; D005136:Eye Proteins; C084884:Nrl protein, mouse; D011518:Proto-Oncogene Proteins; D017978:Receptors, Growth Factor; D051785:Smad Proteins; D015534:Trans-Activators; D051153:Wnt Proteins; D052004:Bone Morphogenetic Protein Receptors