Analysis of optic nerve stroke by retinal Bex expression

[摘要] Purpose: Few proteins are known to be selectively expressed inretinal ganglion cells (RGCs), the neurons directly affected by opticnerve stroke and glaucoma. In addition, subsets of RGCs are reported toproject to various CNS areas via the retinohypothalamic pathway inrodents and primates. Many of these areas exhibit immunoreactivity forthe brain-expressed X-linked (Bex) proteins Bex1 and Bex2. This promptedus to evaluate expression of these proteins in retina.Methods: We utilized rats and transgenic mice, coupled with a newrodent model of isolated optic nerve stroke (rodent anterior ischemicoptic neuropathy, rAION). An anti-Bex1 antibody was reacted to retinaltissue extracts. To evaluate short term effects of rAION on RGC Bexexpression, a double transgenic mouse strain was employed expressingcyan fluorescent protein (CFP) under control of the Thy-1 proteinpromotor, and beta-galactosidase (lacZ) under control of theimmediate early stress c-fos gene promotor. Positive identificationof rat RGCs was performed by retrograde fluorogold labeling viastereotactic CNS injection. Retinas were analyzed using bothdiaminobenzidine (DAB)-linked immunochemistry and confocal microscopy.Results: Bex immunoreactivity is present at high levels in theretina. Bex1 and Bex2 are selectively expressed in RGCs anddifferentially expressed in a subset of large RGC neurons. Bex signallevels are lower in small RGC neurons, which preferentially express highlevels of the transcription factor Brn3b. Post-stroke, Bex accumulatesin the RGC cytoplasm, consistent with the optic nerve edema produced byclinical AION.Conclusions: Bex immunoreactivity can be used to evaluate, ex vivo,the distribution of RGC cell bodies and their axons in the retina andrAION effects on RGC axonal loss. Thus, Bex can be utilized to evaluateboth long- and short-term effects of optic nerve stroke and may play asignificant role in regulating RGC functions in both the axonal and cellbody components of RGC neurons.

[学科分类] 生物化学/生物物理