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Patterns of missplicing caused by RB1 gene mutations in patients with retinoblastoma and association with phenotypic expression
Author(s) -
Zhang Katherine,
Nowak Inga,
Rushlow Diane,
Gallie Brenda L.,
Lohmann Dietmar R.
Publication year - 2008
Publication title -
human mutation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 162
eISSN - 1098-1004
pISSN - 1059-7794
DOI - 10.1002/humu.20664
Subject(s) - biology , exon , splice site mutation , genetics , intron , gene , exon skipping , mutation , splice , missense mutation , point mutation , rna splicing , phenotype , microbiology and biotechnology , alternative splicing , rna
Abstract We have analyzed RNA from retinoblastoma patients and unaffected carriers with various RB1 gene mutations to determine the patterns of missplicing and associations with phenotypic expression. Most sequence alterations in or in the neighborhood of conserved splice signals that we tested resulted in simple exon skipping (15 mutations) or intron inclusion (new acceptor AG‐sites, four mutations) as expected. Two mutations resulted in skipping of a neighboring exon (exon 11), a complex pattern indicating competition for correct lariat formation. We observed no activation of a cryptic splice site but found that a recurrent missense mutation in exon 7 creates a new splice site (two families). RT‐PCR analysis enabled us to confirm the presence and to characterize the transcriptional consequences of gross insertions and deletions in the RB1 gene in six patients, including two patients with mutational mosaicism. We also used RT‐PCR analysis to search for unknown mutations in 15 patients and identified three oncogenic point mutations deep in introns. Two of these mutations are recurrent thus indicating that, despite the vast extent of the introns of the RB1 gene, few bases are effective targets for oncogenic mutations. When analyzing associations between phenotypic expression (16 families) and mutational consequences we observed no link to the presence or absence of a premature termination codon in the mutant transcript. However, the location of a mutation relative to the splice sequence has a strong and consistent influence on phenotypic expression. Hum Mutat 29(4), 475–484, 2008. © 2008 Wiley‐Liss, Inc.