Schoen T J, Bondy C A, Zhou J, Dhawan R, Mazuruk K, Arnold D R, Rodriguez I R, Waldbillig R J, Beebe D C, Chader G J
Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Invest Ophthalmol Vis Sci. 1995 Dec;36(13):2652-62.
To determine the developmental expression and localization of mRNA for insulin-like growth factor binding protein-2 (IGFBP-2), a major binding protein of IGF-I and IGF-II, in ocular tissues of the embryonic and early posthatched chick.
In situ hybridization and northern blot analysis were used to analyze the cellular origin and relative expression of IGFBP-2 mRNA in ocular tissues.
Wholemount in situ hybridization reveals that, as early as 3.5 days of embryonic development (E3.5), IGFBP-2 mRNA is already expressed in many areas of the embryo, including surface ectoderm, certain regions of the brain, pharyngeal clefts, somites, and limb buds. In the eye, IGFBP-2 mRNA is expressed only in the presumptive corneal epithelium at this time. By E6, IGFBP-2 mRNA expression is present in both the corneal epithelium and endothelium. By E12, IGFBP-2 mRNA is detected clearly in the corneal stroma as well as in several other ocular structures, such as the sclera, eyelid, and ciliary body. In the neural retina, a low, diffuse expression of IGFBP-2 mRNA is found at E6, which becomes more localized to the nuclear layers by E12. Northern blot analysis confirms that a high level of IGFBP-2 expression is present in the cornea and sclera by E8 to E12. A high level of IGFBP-2 mRNA expression, however, is not observed in the retina until E18. At posthatch day 2 (P2), northern blot analyses of ocular tissues reveal that the cornea contains the highest ocular level of IGFBP-2 mRNA expression, a value equal to that of brain and liver.
The early appearance, along with differential temporal and spatial expression of IGFBP-2 mRNA in developing ocular tissues, suggests a role for IGFBP-2 in the regulation of growth and differentiation of several ocular tissues, including the cornea, sclera, and retina.
