title: Two independent RB1-inactivating mutations in peripheral blood DNA of a hereditary retinoblastoma patient.
abstract: We report the presence of a hemizygous inactivating germ-line RB1 mutation (a recurrent g.78250C-->T transition, resulting in a stop codon in exon 17) in peripheral blood DNA from a patient with hereditary bilateral retinoblastoma. Hemizygosity was established by sequencing that showed no traces of the wild-type C nucleotide and by quantitative real-time PCR, which showed loss of one copy of exon 17. Genotyping of the RB1 locus with several polymorphic markers delineated a maximal deletion region between g.76875 and g.99426, including exons 15-17 and a large piece (21 kb) of intron 17. The heterozygosity for the mutation found in skin fibroblasts proves that the intragenic RB1 deletion probably took place in the definitive hematopoietic lineage of the patient. The presence of a null Rb-/- genotype in the hematopoietic cell lineage suggests that the white blood cells of the proband could be useful in the investigation of the role of complementary RBI family proteins in the control of the cell cycle.
authors.affiliation: OncoLab, Unidad de Biología Molecular y Celular del Cáncer, Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM, Madrid, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Alonso
authors.forename: Ibis
authors.initials: I
authors.lastname: Menéndez
authors.forename: Andrés
authors.initials: A
authors.lastname: López
authors.forename: Helena
authors.initials: H
authors.lastname: Frayle
authors.forename: Nora
authors.initials: N
authors.lastname: Ruisánchez
authors.forename: Angel
authors.initials: A
authors.lastname: Pestaña
mesh_terms: D001773:Blood Cells / Q000737:chemistry; D002675:Child, Preschool; D002874:Chromosome Mapping / Q000379:methods; D004252:DNA Mutational Analysis / Q000379:methods; D004273:DNA, Neoplasm / Q000235:genetics; D005091:Exons / Q000235:genetics; D005260:Female; D016161:Genes, Retinoblastoma / Q000235:genetics; D005820:Genetic Testing; D018095:Germ-Line Mutation / Q000235:genetics*; D006801:Humans; D008297:Male; D010375:Pedigree; D019572:Retinal Neoplasms / Q000097:blood / Q000235:genetics*; D012175:Retinoblastoma / Q000097:blood / Q000235:genetics*; D016160:Retinoblastoma Protein / Q000172:deficiency* / Q000235:genetics
chemical_list: D004273:DNA, Neoplasm; D016160:Retinoblastoma Protein