A Review on the Methods for Identification of Mutations in the Tumour Suppressor Gene Retinoblastoma RB1

Abstract

Retinoblastoma is the most common intraocular cancer of childhood. RB1 is the gene responsible for causing retinoblastoma, spans more than 180 kilobases (kb) located on chromosome 13q14, which consist of 27 exons. Retinoblastoma in children may either be hereditary or non-hereditary. Mutations in RB1 gene are mostly point mutations of non-sense or missense type but could also be of frameshift type. These mutations can be identified from both blood and tumour samples by Sanger sequencing and other molecular identification techniques such as Multiplex Ligation-dependent Probe Amplification (MLPA). ‘Fragile’ codons are codons which gets point mutated to form stop codons so that the resulting protein will be incomplete or immature. In RB1, fragile codons get mutated predominantly and lead to the truncation of RB1 protein. The frequent mutations that predominantly occur in the arginine (CGA) codon, wherein changes in the single nucleotide results in the stop (UGA) codon, than any other fragile codon. The present paper reviews the role of RB1 mutations in retinoblastoma and the methods to identify it. We also make an attempt to identify the fragile codons in the RB genome based on the NCBI reference sequence NM_000321.2