Immunoreactivity of the Septins SEPT4, SEPT5, and SEPT8 in the Human Eye

Abstract

Abstract: : Purpose: Septins are a novel family of GTP–binding proteins broadly distributed in many eukaryotes. It has become apparent that they are essential for active membrane movement such as cytokinesis and vesicle trafficking, moreover, they play a role in oncogenesis. In non–dividing cells such as platelets and neurons septins are implicated in exocytosis. We aimed to examine the distribution of SEPT4, SEPT5 and SEPT8 in the human eye. Methods: For each septin, 5–6 normal human eyes were examined by immunohistochemical staining of paraffin sections, using polyclonal antibodies against SEPT4, SEPT5 and SEPT8 and an ABC–detection system. Results: SEPT4 immunoreactivity (IR) was detected primarily in the epithelium of cornea, lens, and non–pigmented ciliary epithelium, in the endothelium of cornea and vessels of iris and retina, as well as in the retinal nerve fiber layer, the outer plexiform layer, the outer segments of the photoreceptor cells, the inner limiting membrane of the optic nerve head and optic nerve axons. SEPT5–IR was present in corneal endothelial cells, iris tissue, non–pigmented ciliary epithelium and epithelial cells of the lens. SEPT8–IR almost paralleled that of SEPT4 except for a lower SEPT8–IR of the outer photoreceptor segments and a positive staining of the meningothelial cell nests in the subarachnoidal space of the bulbar segment of the orbital optic nerve. Conclusions: SEPT4, SEPT5, and SEPT8 are expressed in various ocular tissues, each revealing a distinct expression pattern. Both physiological and potential pathophysiological role of septins in the human eye deserve further investigation.

Keywords: immunohistochemistry • anatomy • oncology