Novel mutations in the XLRS1 gene may be caused by early Okazaki fragment sequence replacement.
OBJECTIVE
To determine whether two families diagnosed with X-linked retinoschisis contained mutations in the XLRS1 gene.


METHODS
DNA from the patients was obtained from blood lymphocytes using commercially available kits. Single-strand conformation assay was performed in an electrophoresis apparatus using 10% acrylamide TBE gels at 10 degrees C. The gels were stained with SYB green II and were scanned in a phosphoimager. DNA was sequenced using an automated fluorescence sequencer.


RESULTS
A deletion that eliminates exon 2 was found in one family. An abnormal sequence replacement in exon 4 was found in the other family. Both mutations have severe effects in the coding region by inserting premature stop codons.


CONCLUSIONS
Both of the families have mutations in the XLRS1 gene. One of these mutations points to a novel mechanism. The mutation is caused by a replacement of 17 bp of a normal sequence with 20 bp of a sequence originating from two different places in the antisense strand. This suggests that early Okazaki fragments were incorporated into the sense strand of exon 4, replacing the normal sequence.
National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
I R
IR
Rodriguez
K
K
Mazuruk
C
C
Jaworski
F
F
Iwata
E F
EF
Moreira
M I
MI
Kaiser-Kupfer
D000328:Adult; D001483:Base Sequence; D002648:Child; D004247:DNA / Q000032:analysis*; D004252:DNA Mutational Analysis; D004591:Electrophoresis, Polyacrylamide Gel; D005091:Exons; D005136:Eye Proteins / Q000235:genetics*; D005260:Female; D008040:Genetic Linkage; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D010375:Pedigree; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D012164:Retinal Diseases / Q000235:genetics*; D017384:Sequence Deletion; D014960:X Chromosome / Q000235:genetics
D005136:Eye Proteins; C108726:RS1 protein, human; D004247:DNA