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Aims: To describe the clinical phenotype of X linked juvenile retinoschisis in eight Italian families with six different mutations in the XLRS1 gene. Methods: Complete ophthalmic examinations, electroretinography and A and B-scan standardised echography were performed in 18 affected males. The coding sequences of the XLRS1 gene were amplified by polymerase chain reaction and directly sequenced on an automated sequencer. Results: Six different XLRS1 mutations were identified; two of these mutations Ile81Asn and the Trp122Cys, have not been previously described. The affected males showed an electronegative response to the standard white scotopic stimulus and a prolonged implicit time of the 30 Hz flicker. In the families with Trp112Cys and Trp122Cys mutations we observed a more severe retinoschisis (RS) clinical picture compared with the other genotypes. Conclusion: The severe RS phenotypes associated with Trp112Cys and to Trp122Cys mutations suggest that these mutations determine a notable alteration in the function of the retinoschisin protein.

Juvenile retinoschisis is an X‐linked recessive disease caused by mutations in the XLRS1 gene. We screened 31 new unrelated patients and families for XLRS1 mutations in addition to previously reported mutations for 60 of our families (Retinoschisis Consortium, Hum Mol Genet 1998;7:1185–1192). Twenty‐three different mutations including 12 novel ones were identified in 28 patients. Mutations identified in this study include 19 missense mutations, two nonsense mutations, one intragenic deletion, four microdeletions, one insertion, and one intronic sequence substitution that is likely to result in a splice site defect. Two novel mutations, c.38T→C (L13P) and c.667T→C (C223R), respectively, present the first genetic evidence for the functional significance of the putative leader peptide sequence and for the functional significance at the carboxyl terminal of the XLRS1 protein beyond the discoidin domain. Mutations in 25 of the families were localized to exons 4–6, emphasizing the critical functional significance of the discoidin domain of the XLRS1 protein. Hum Mutat 14:423–427, 1999. © 1999 Wiley‐Liss, Inc.

We examined the XLRS1 gene for mutations in 6 Japanese patients with X-linked juvenile retinoschisis from a total of three families (5 males and 1 female), and from 3 obligate carrier females. DNA was amplified for all six coding exons of the XLRS1 gene with established primer pairs, and was sequenced directly. Each family had a different mutation, Trp96stop, 522+1g→a, and Lys167Asn in the XLRS1 gene. Affected patients had a hemizygous mutant allele while the obligate carrier females were heterozygotes who had both wild-type and mutant-type alleles. A proband female, who was the offspring of asymptomatic and nonconsanguineous parents, was found to have a chromosomal karyotype (45, X) that was indicative of Turner’s syndrome. These three different mutations in the XLRS1 gene have not been previously reported. Further studies are needed to determine the relationship between these defects in the XLRS1 gene and the phenotypic expression of the disease.