Background and aims: Mutations in RB1 gene may lead to retinoblastoma which is the most common solid intraocular tumor in under-six year old children. To date, a wide spectrum of the mutations has been reported in the splicing ofRB1 which either affect splicing sequences or splicing regulatory elements. This report introduces a new mutation inRB1 and its influence on the splicing of mRNA.
Case report: In the present survey, mutation analysis was done in an Iranian patient with sporadic unilateral retinoblastoma using direct sequencing and MLPA. Also, RB1 gene splicing pattern was analyzed by RT-PCR method. As a result, a same-sense nucleotide change (g.70 320C>T) was found near the 5' end of exon 12. This alteration disrupts the consensus sequence of an exonic splicing enhancer and changes the binding site of SC-35 protein. Structural analysis of cDNA in this patient showed the disruption of normal splicing pattern and the skipping of exon 12 from theRB1 transcript.
Conclusion: Based on these findings, it may be reasonable to conclude that the above nucleotide change could be a pathogenic mutation. Also, for the first time we report an evidence for the presence of an exonic splicing enhancer in the exon 12 of theRB1 gene.