C.332C＞T, A New Site Of Mutation Of X Linked Retinoschsis And Its Pathogenesis

Background and Objective: XLRS (X-Linked Retinoschisis), also calledCongenital Retinoschsis,mainly affects male juveniles and cause their maculardegeneration. The condition is mainly X chromosome linked recessively hereditary,and the mutations of its gene XLRS1（X-Linked Retinoschisin1, NCBI Gene ID:6247）are inherited from carrier females to their descendants. However, there are alsofew reports of autosomal dominant retinoschisis. This article discovered a newmutation site of XLRS by investigating a case of this condition, and made somefurther research, trying to elucidate the pathogenesis of this new mutant.Method: A seven years old, XLRS affected boy was clinically diagnosed by visualacuity, direct ophthalmoscopy, OCT (Optical Coherence Tomography) examinationand ERG (Electroretinography). Subsequently, six exons of XLRS1were sequencedby extracting DNA from the boy and his parents, to confirm the site of mutation andits hereditary model. Further research include constructing a cell line of293Tconstitutively expressing RS1(Retinoschisin) tagged with the fusion protein3×FLAG, and investigating the expression pattern and polymerization of RS byreducing and non-reducing SDS-PAGE (Sodium Dodecyl Sulphate-PolyacrylamideGel Electrophoresis).Results: This affected boy was confirmed to have a point mutation, which locates inthe332ndbp of the CDS (Coding Sequence) of XLRS1, from C (Cytosine) to T(Thymine)（c.332C>T），while his mother has both of the wild type of C and themutant T alleles, but his father has no mutation. Two cell lines of293T expressingwild type and mutant type of RS1were successfully constructed by puromycin screening. Finally, it is confirmed that the mutant RS could not be secreted from293T.Conclusions: c.332C>T, a new site of mutation of X Linked Retinoschsis wasidentified, which conform to the pattern of the X chromosome linked recessiveheredity, and maybe the secretion incompetency of mutant RS1led to XLRS.