Targeted Screening of RB1 Exon 18 in Sudanese Children with Retinoblastoma: A Molecular and Bioinformatics Study.

Background: Retinoblastoma (RB) is the most common intraocular malignancy in early childhood. It is most often related to mutations in the RB1 gene, with an incidence of 3% of all pediatric tumors. Methods: Thirty-one (n=31) clinically and histopathological diagnosed cases of RB attending Makkah Eye Complex Orbit clinic (Khartoum, Sudan) were included in this Molecular Genetic RB Analysis. Fresh blood samples were collected, from seven RB patients and 15 close families, for DNA extraction and PCR products were sent for Genetic Sequencing and Bioinformatics approach for “Exon 18 mutations” which is a known mutational hotspot globally. Results: Most patients (41.9%) were under five years old. Females were 58.1% and males were 41.9%. Leukocoria was the most common sign at presentation (41.9%). RB unilaterality was 77.4% while bilaterality was 19.4%. Both eyes were equally affected (50% each). The age at the time of diagnosis ranged from seven days to five years old. Consanguinity of parents was very high (85.7%); 1st degree cousins were much lower (28.6%) than 2nd degree cousins (57.1%). The patients’ ethnic background and geographical area were from seven different tribes; all belong to Western Sudan. The Functional Analysis and Single Nucleotide Polymorphisms (SNPs) prediction study of exon 18 from NCBI data base showed that the various computational approaches used (SIFT, PolyPhen-2, I-mutant and Project hope) identified 16 reported mutations worldwide, three of which (rs137853292, rs375645171 and rs772068738) are major nsSNPs (non-synonymous) which might contribute to native RB1 protein malfunction and ultimately causing carcinoma (Additional file 2). Our molecular genetic study showed that no mutations were detected in exon 18 among the Sudanese RB patients and their relatives Conclusion: RB mainly affected children under five years of age, and both sexes were equally affected. Unilaterality was predominant. Consanguinity plays a role in inheritance and most patients were from Western Sudan. The most detected deleterious mutations worldwide in exon 18 were not found in the Sudanese studies samples. Further studies targeting other frequently mutated exons (e.g., exons 8, 10, and 14) or employing next-generation sequencing (NGS) are recommended. Bioinformatics tools are useful in studying the functional analysis of SNPs.