Abstract
Purpose::
To analyze the retinal gene expression profiles after optic nerve transection (ONT) and to identify genes expressed in ganglion cells (RGCs).
Methods::
An axotomy animal model was generated by transection of the optic nerve with care not to damage the adjacent blood supply. The extent of cell loss was evaluated by counting cells in the ganglion cell layer (GCL) of flat-mounted retinas stained with cresyl violet. Gene expression profiles of control and ONT retinas were analyzed. Real-time RT-PCR was used to analyze changes in gene expression levels. In situ hybridization and immunohystochemistry were used to localize expression of genes of interest in the retina.
Results::
Several novel genes expressed in the GCL have been identified and their expression patterns in different tissues were analyzed. Three of these genes (XM 214677, AW529036, and BF404316) were shown with in situ hybridization/immunohistochemistry to be expressed in RGCs. XM 214677 encodes a protein containing a p25-alpha domain, which is characteristic to the family encoding a 25 kDa protein phosphorylated by a Ser/Thr-Pro kinase. AW529036 showed 93% similarity to mouse NM_177572, encoding a 380-amino acid hypothetical protein that contains an ATP binding domain. BF404316 is 88% homologous to the mouse tripartite motif containing 36 (Trim36).Thirteen differentially expressed genes in the ONT model characterized by RGC degeneration were mapped to the known loci associated with glaucomatous neuropathy. These include myocilin, and quiescin Q6 localized to1q24, the GLC1A locus for POAG; Fas apoptotic inhibitory molecule, ceruloplasmin, and transferrin mapped to 3q22.1, a GLC1C locus for POAG; acidic cysteine rich glycoprotein localized to 5q31, a locus for JOAG; endothelin converting enzyme 1, G-binding protein beta-1, 3-hydroxy-3-methylglutaryl CoA lyase, and enolase 1 alpha localized to 1p36, the GLC3B locus for the PCG; vasopressive intestinal peptide receptor 2 mapped to 7q36.3, the GLC1F and GPDS1 loci for POAG and pigmentary glaucoma, respectively; acetyl-CoA acyltransferase 2, retina and anterior neural fold homeobox, transthyretin, and parvalbumin mapped to GPDS2 locus for pigmentary glaucoma.
Conclusions::
Several novel genes expressed in the GCL, including three genes expressed in RGCs, have been identified and their expression patterns in different tissues were analyzed. Furthermore, genes differentially regulated in the retinas with axotomy-induced RGC death and mapped to known glaucoma loci may be considered for mutation screening in patients with inherited forms of this neuropathy.
Keywords: ganglion cells • gene/expression • in situ hybridization