<it>RB1 </it>gene mutation up-date, a meta-analysis based on 932 reported mutations available in a searchable database

• Main Authors: Pestaña Ángel, Palacios Itziar, Alonso Javier, Valverde José R
• Format: Article
• Language: English
• Published: BMC 2005-11-01
• Series: BMC Genetics
• Online Access: http://www.biomedcentral.com/1471-2156/6/53

<p>Abstract</p> <p>Background</p> <p>Retinoblastoma, a prototype of hereditary cancer, is the most common intraocular tumour in children and potential cause of blindness from therapeutic eye ablation, second tumours in germ line carrier's survivors, and even death when left untreated. The molecular scanning of <it>RB1 </it>in search of germ line mutations lead to the publication of more than 900 mutations whose knowledge is important for genetic counselling and the characterization of phenotypic-genotypic relationships.</p> <p>Results</p> <p>A searchable database (RBGMdb) has been constructed with 932 published <it>RB1 </it>mutations. The spectrum of these mutations has been analyzed with the following results: 1) the retinoblastoma protein is frequently inactivated by deletions and nonsense mutations while missense mutations are the main inactivating event in most genetic diseases. 2) Near 40% of <it>RB1 </it>gene mutations are recurrent and gather in sixteen hot points, including twelve nonsense, two missense and three splicing mutations. The remainder mutations are scattered along <it>RB1</it>, being most frequent in exons 9, 10, 14, 17, 18, 20, and 23. 3) The analysis of <it>RB1 </it>mutations by country of origin of the patients identifies two groups in which the incidence of nonsense and splicing mutations show differences extremely significant, and suggest the involvement of predisposing ethnic backgrounds. 4) A significant association between late age at diagnosis and splicing mutations in bilateral retinoblastoma patients suggests the occurrence of a delayed-onset genotype. 5) Most of the reported mutations in low-penetrance families fall in three groups: a) Mutations in regulatory sequences at the promoter resulting in low expression of a normal Rb; b) Missense and in-frame deletions affecting non-essential sequence motifs which result in a partial inactivation of Rb functions; c) Splicing mutations leading to the reduction of normal mRNA splicing or to alternative splicing involving either true oncogenic or defective (weak) alleles.</p> <p>Conclusion</p> <p>The analysis of <it>RB1 </it>gene mutations logged in the RBGMdb has shown relevant phenotype-genotype relationships and provided working hypothesis to ascertain mechanisms linking certain mutations to ethnicity, delayed onset of the disease and low-penetrance. Gene profiling of tumors will help to clarify the genetic background linked to ethnicity and variable expressivity or delayed onset phenotypes.</p>