Immunohistochemical Localization of Transglutaminase 4 in the Human Eye

ABSTRACT

PURPOSE: Transglutaminase 4 (TGase 4) belongs to a family of enzymes that catalyzes the post-translational modification of proteins. In an attempt to establish its physiological function(s), the distribution of TGase 4 expression in the human eye was determined. METHODS: Ocular tissues obtained from five human whole eyeball postmortem (40(+1) weeks at gestation age, 2 months, 48, 66, 76 years) were stained with monoclonal antibodies against human TGase 4 using indirect immunohistochemical method. RESULTS: TGase 4 was found in the lacrimal glands, corneal epithelium and endothelium, conjunctival epithelium, lens epithelium, retina (inner segment of photoreceptor, external limiting membrane, outer plexiform layer, inner plexiform layer, retinal nerve fiber layer and internal limiting membrane), iris, ciliary muscle, ciliary nonpigmented epithelium and trabecular meshwork. Endothelium of blood vessels in all ocular tissues was also stained. Conjunctival stroma, choroid, anterior tenon's capsule were faintly stained. No evidence of immunostaining for TGase 4 was found in the corneal stroma, iris stroma, lens nucleus, ciliary process, sclera, extraocular muscle and optic nerve. CONCLUSIONS: The expression pattern of TGase 4 was different from those of other TGase isoforms in the human eye. This result may be helpful in further investigation of the role of TGase 4 in the ocular tissue.