Congenital X–Linked Retinoschisis: New Observations and Therapeutic Implications

Abstract

Abstract: : Purpose: An analysis of the intraschisis cavity fluid and vitreous samples of children with retinoschisis, vitreoretinal dystrophies, and normal pediatric vitreous, and its therapeutic implication are presented. Methods: Schisis fluid samples were obtained undiluted from the schisis cavity using a 39 gauge cannula. In addition, undiluted vitreous samples were collected from 5 eyes with congenital X–linked retinoschisis and familial exudative vitreoretinopathy and normal vitreous sample taken at the time of congenital cataract surgery. Protein levels were measured in duplicate using the Pierce BCA method. Protein composition of the schisis and vitreous samples were determined using one–dimensional SDS polyacrylamide gel electrophoresis with 5%, 7.5%, and 12% gels. Specific protein bands of interest were excised from the gels. The proteins were extracted from the gel, enzyme digested, and the peptides sequenced by Nanospray–mass spectroscopy. The obtained sequences were submitted to database searching (SwissProt and NCBI) to obtain identification. Results: Protein concentrations were 4.0 mg/ml for the undiluted vitreous and 2.4 and 4.2 mg/ml for the schisis fluid samples. SDS–PAGE showed that schisis fluid samples were very similar to vitreous samples in protein composition and in the relative abundance of specific proteins. Two bands (200 kD and 18 kD) that were absent from the vitreous, however, were seen in the schisis cavity samples. These samples were compared against the samples of other dystrophies, specifically familial exudative vitreoretinopathy, and also compared against normal pediatric vitreous. Conclusions: The similarity in protein composition of schisis and vitreous samples in congenital X–linked retinoschisis suggests that soluble vitreous proteins can easily diffuse through the portion of the inner retina separating the two cavities. This also suggests that manipulation of the vitreous cavity including positioning of a substance with less potential for diffusion may make it possible to control the size of schisis cavities.

Keywords: retinopathy of prematurity • proteomics