Bioinformatic and statistical analysis of a primate model of ocular hypertension

The transcriptional events preceding clinical cupping of the optic disc and tissue remodeling at the optic nerve head in human glaucoma are largely unknown and were the focus of the present investigation. Using oligonucleotide microarrays, we identified differentially expressed genes in astrocytes of the optic nerve head in a nonhuman primate model of ocular hypertension, and in spontaneous open angle glaucoma in a nonhuman primate. Disease progression was evaluated using axon counts, fundus photography, and GDx VCC scans. Twenty-two genes were identified as being significantly differentially expressed between control and experimental groups of cynomolgus macaques (Macaca mulata ). A bioinformatic approach predicted cell-specific expression by the cellular populations of the primate optic nerve head. Selected genes were confirmed by qRT-PCR and immunohistochemistry.; Two previously published datasets from our laboratory were also reanalyzed and overlapping differentially expressed genes across multiple studies were prioritized for further investigation. Many differentially expressed genes have presumptive roles in motility and extracellular matrix remodeling, including CAPG, and GPNMB. CAPG is a gelsolin family member that has been shown to affect cell motility. GPNMB, a transmembrane glycoprotein, is one of two null mutations in the DBAl2J mouse, which develops iris stromal atrophy (ISA) and pigment dispersion syndrome (PDS). The null mutation in gpnmb of the DBA12J mouse was previously mapped to PDS. Another set of differentially expressed genes from the primate model has established roles in neurite extension and regeneration, and immunohistochemical analysis of NEFH and GAP43 indicated that RGC axons may make regenerative sprouting attempts in glaucoma.; By oligonucleotide microarray, GPNMB was also differentially expressed in pure astrocyte cultures from healthy and glaucomatous Caucasian American donors, and in healthy donor astrocyte cultures exposed to elevated hydrostatic pressure for twenty-four hours. These results suggest a putative role for GPNMB in the severity and progression of optic nerve head excavation in human glaucoma, particularly in the context of astrocyte migration and extracellular matrix remodeling. Preliminary investigations into the transcriptional regulation of GPNMB indicated that regulatory elements for pressure-induced activation are not within the first two kilobases of the transcriptional start site.