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WAI KIT CHU, Bining Zhang, Pancy Oi Sin Tam, Li Jia Chen, Tommy Chung Yan Chan, Vishal Jhanji, Chi Pui Pang; Functional study of RAD21 mutation identified in a sclerocornea pedigree. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1421.
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Sclerocornea is an abnormality of opacity at the peripheral part or the entire surface of a cornea. Those patients with sclerocornea affecting the whole corneal surface area usually suffer complete blindness. And those with peripheral sclerocornea would still have visual field restriction. Currently there is no medication to treat sclerocornea. Corneal transplantation is the only treatment to restore vision. Given the limited supply of cornea for transplantation, there is a need to understand the disease mechanism of sclerocornea for the development of alternative treatments.
A Chinese family showing peripheral sclerocornea-like characteristics in six individuals over three generations out of nineteen family members was identified. Blood was taken from four affected and one unaffected family members. Genomic DNA was extracted for exome sequencing. Peripheral blood mononuclear cells (PBMC) were extracted from blood using Ficoll-Paque and transformed with Epstein–Barr virus. The transformed cells were characterized by staining with B-cell marker CD23 and analyzed by flow cytometry. Allele-specific gene expression was studied by reverse-transcription DNA sequencing. Chromosomes were stained with Giemsa and counted under a light microscope. Statistics was done by using t-test and p < 0.05 was used to reflect statistical significance.
Heterozygous mutation in RAD21 was identified only in affected family members but not in the unaffected family members. These affected family members expressed both the wild-type and mutated RAD21 alleles. In the five transformed PBMC (four affected and one unaffected family members), 97.1% +/- 1.83% of the cell population stained positively with the CD23 marker. There was no significant difference in chromosome numbers between the affected and unaffected PBMC (p > 0.05).
We have identified a heterozygous mutation in RAD21in a Chinese family showing peripheral sclerocornea-like characteristics. RAD21 involves in sister chromatid separation and genome stability. However, the chromosome numbers remain normal in the affected family members. Further work will be done in studying the roles of RAD21 in sclerocornea.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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